lua: Update to 5.4.6vendor/lua/5.4.6

Sponsored by:		Netflix

49 files changed, 3355 insertions, 866 deletions

diff --git a/Makefile b/Makefile
index fef1af4821e6..8efa2eb3fdd6 100644
--- a/Makefile
+++ b/Makefile
@@ -36,7 +36,7 @@ RM= rm -f
 # == END OF USER SETTINGS -- NO NEED TO CHANGE ANYTHING BELOW THIS LINE =======
 
 # Convenience platforms targets.
-PLATS= guess aix bsd c89 freebsd generic linux linux-readline macosx mingw posix solaris
+PLATS= guess aix bsd c89 freebsd generic ios linux linux-readline macosx mingw posix solaris
 
 # What to install.
 TO_BIN= lua luac
@@ -46,7 +46,7 @@ TO_MAN= lua.1 luac.1
 
 # Lua version and release.
 V= 5.4
-R= $V.4
+R= $V.6
 
 # Targets start here.
 all:	$(PLAT)
diff --git a/README b/README
index c394c69828b5..1ae97165babe 100644
--- a/README
+++ b/README
@@ -1,5 +1,5 @@
 
-This is Lua 5.4.4, released on 13 Jan 2022.
+This is Lua 5.4.6, released on 02 May 2023.
 
 For installation instructions, license details, and
 further information about Lua, see doc/readme.html.
diff --git a/doc/contents.html b/doc/contents.html
index ab82eb4a9278..1231e6d2481d 100644
--- a/doc/contents.html
+++ b/doc/contents.html
@@ -32,7 +32,7 @@ For a complete introduction to Lua programming, see the book
 
 <P>
 <SMALL>
-Copyright &copy; 2020&ndash;2022 Lua.org, PUC-Rio.
+Copyright &copy; 2020&ndash;2023 Lua.org, PUC-Rio.
 Freely available under the terms of the
 <A HREF="http://www.lua.org/license.html">Lua license</A>.
 </SMALL>
@@ -85,6 +85,8 @@ Freely available under the terms of the
 <LI><A HREF="manual.html#3.4.9">3.4.9 &ndash; Table Constructors</A>
 <LI><A HREF="manual.html#3.4.10">3.4.10 &ndash; Function Calls</A>
 <LI><A HREF="manual.html#3.4.11">3.4.11 &ndash; Function Definitions</A>
+<LI><A HREF="manual.html#3.4.12">3.4.12 &ndash; Lists of expressions, multiple results, and adjustment<A>
+
 </UL>
 <LI><A HREF="manual.html#3.5">3.5 &ndash; Visibility Rules</A>
 </UL>
@@ -613,7 +615,7 @@ Freely available under the terms of the
 <A HREF="manual.html#pdf-LUA_HOOKLINE">LUA_HOOKLINE</A><BR>
 <A HREF="manual.html#pdf-LUA_HOOKRET">LUA_HOOKRET</A><BR>
 <A HREF="manual.html#pdf-LUA_HOOKTAILCALL">LUA_HOOKTAILCALL</A><BR>
-<A HREF="manual.html#pdf-LUAL_BUFFERSIZE">LUAL_BUFFERSIZE</A><BR>
+<A HREF="manual.html#pdf-LUA_LOADED_TABLE">LUA_LOADED_TABLE</A><BR>
 <A HREF="manual.html#pdf-LUA_MASKCALL">LUA_MASKCALL</A><BR>
 <A HREF="manual.html#pdf-LUA_MASKCOUNT">LUA_MASKCOUNT</A><BR>
 <A HREF="manual.html#pdf-LUA_MASKLINE">LUA_MASKLINE</A><BR>
@@ -641,6 +643,7 @@ Freely available under the terms of the
 <A HREF="manual.html#pdf-LUA_OPSHR">LUA_OPSHR</A><BR>
 <A HREF="manual.html#pdf-LUA_OPSUB">LUA_OPSUB</A><BR>
 <A HREF="manual.html#pdf-LUA_OPUNM">LUA_OPUNM</A><BR>
+<A HREF="manual.html#pdf-LUA_PRELOAD_TABLE">LUA_PRELOAD_TABLE</A><BR>
 <A HREF="manual.html#pdf-LUA_REFNIL">LUA_REFNIL</A><BR>
 <A HREF="manual.html#pdf-LUA_REGISTRYINDEX">LUA_REGISTRYINDEX</A><BR>
 <A HREF="manual.html#pdf-LUA_RIDX_GLOBALS">LUA_RIDX_GLOBALS</A><BR>
@@ -657,6 +660,7 @@ Freely available under the terms of the
 <A HREF="manual.html#pdf-LUA_TUSERDATA">LUA_TUSERDATA</A><BR>
 <A HREF="manual.html#pdf-LUA_USE_APICHECK">LUA_USE_APICHECK</A><BR>
 <A HREF="manual.html#pdf-LUA_YIELD">LUA_YIELD</A><BR>
+<A HREF="manual.html#pdf-LUAL_BUFFERSIZE">LUAL_BUFFERSIZE</A><BR>
 
 </TD>
 </TR>
@@ -664,10 +668,10 @@ Freely available under the terms of the
 
 <P CLASS="footer">
 Last update:
-Thu Jan 13 11:32:22 UTC 2022
+Sat Apr  1 17:57:05 UTC 2023
 </P>
 <!--
-Last change: revised for Lua 5.4.4
+Last change: revised for Lua 5.4.5
 -->
 
 </BODY>
diff --git a/doc/lua.1 b/doc/lua.1
index a46a1a67dd04..3f472fd81f62 100644
--- a/doc/lua.1
+++ b/doc/lua.1
@@ -1,5 +1,5 @@
-.\" $Id: lua.man,v 1.14 2020/05/21 19:31:21 lhf Exp $
-.TH LUA 1 "$Date: 2020/05/21 19:31:21 $"
+.\" $Id: lua.man,v 1.14 2022/09/23 09:06:36 lhf Exp $
+.TH LUA 1 "$Date: 2022/09/23 09:06:36 $"
 .SH NAME
 lua \- Lua interpreter
 .SH SYNOPSIS
@@ -86,11 +86,17 @@ execute statement
 enter interactive mode after executing
 .IR script .
 .TP
-.BI \-l " name"
+.BI \-l " mod"
 require library
-.I name
+.I mod
 into global
-.IR name .
+.IR mod .
+.TP
+.BI \-l " g=mod"
+require library
+.I mod
+into global
+.IR g .
 .TP
 .B \-v
 show version information.
diff --git a/doc/manual.html b/doc/manual.html
index 61a8220d7fd1..0af688b343c7 100644
--- a/doc/manual.html
+++ b/doc/manual.html
@@ -19,7 +19,7 @@ by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, Waldemar Celes
 
 <P>
 <SMALL>
-Copyright &copy; 2020&ndash;2022 Lua.org, PUC-Rio.
+Copyright &copy; 2020&ndash;2023 Lua.org, PUC-Rio.
 Freely available under the terms of the
 <a href="http://www.lua.org/license.html">Lua license</a>.
 </SMALL>
@@ -63,7 +63,7 @@ and rapid prototyping.
 
 <p>
 Lua is implemented as a library, written in <em>clean C</em>,
-the common subset of Standard&nbsp;C and C++.
+the common subset of standard&nbsp;C and C++.
 The Lua distribution includes a host program called <code>lua</code>,
 which uses the Lua library to offer a complete,
 standalone Lua interpreter,
@@ -1379,7 +1379,9 @@ Lua also accepts hexadecimal constants,
 which start with <code>0x</code> or <code>0X</code>.
 Hexadecimal constants also accept an optional fractional part
 plus an optional binary exponent,
-marked by a letter '<code>p</code>' or '<code>P</code>'.
+marked by a letter '<code>p</code>' or '<code>P</code>' and written in decimal.
+(For instance, <code>0x1.fp10</code> denotes 1984,
+which is <em>0x1f / 16</em> multiplied by <em>2<sup>10</sup></em>.)
 
 
 <p>
@@ -1621,21 +1623,13 @@ Expressions are discussed in <a href="#3.4">&sect;3.4</a>.
 <p>
 Before the assignment,
 the list of values is <em>adjusted</em> to the length of
-the list of variables.
-If there are more values than needed,
-the excess values are thrown away.
-If there are fewer values than needed,
-the list is extended with <b>nil</b>'s.
-If the list of expressions ends with a function call,
-then all values returned by that call enter the list of values,
-before the adjustment
-(except when the call is enclosed in parentheses; see <a href="#3.4">&sect;3.4</a>).
+the list of variables (see <a href="#3.4.12">&sect;3.4.12</a>).
 
 
 <p>
 If a variable is both assigned and read
 inside a multiple assignment,
-Lua ensures all reads get the value of the variable
+Lua ensures that all reads get the value of the variable
 before the assignment.
 Thus the code
 
@@ -1739,11 +1733,6 @@ even if this other label has been declared in an enclosing block.
 
 
 <p>
-Labels and empty statements are called <em>void statements</em>,
-as they perform no actions.
-
-
-<p>
 The <b>break</b> statement terminates the execution of a
 <b>while</b>, <b>repeat</b>, or <b>for</b> loop,
 skipping to the next statement after the loop:
@@ -2059,7 +2048,7 @@ function calls are explained in <a href="#3.4.10">&sect;3.4.10</a>;
 table constructors are explained in <a href="#3.4.9">&sect;3.4.9</a>.
 Vararg expressions,
 denoted by three dots ('<code>...</code>'), can only be used when
-directly inside a vararg function;
+directly inside a variadic function;
 they are explained in <a href="#3.4.11">&sect;3.4.11</a>.
 
 
@@ -2074,52 +2063,6 @@ the unary logical <b>not</b> (see <a href="#3.4.5">&sect;3.4.5</a>),
 and the unary <em>length operator</em> (see <a href="#3.4.7">&sect;3.4.7</a>).
 
 
-<p>
-Both function calls and vararg expressions can result in multiple values.
-If a function call is used as a statement (see <a href="#3.3.6">&sect;3.3.6</a>),
-then its return list is adjusted to zero elements,
-thus discarding all returned values.
-If an expression is used as the last (or the only) element
-of a list of expressions,
-then no adjustment is made
-(unless the expression is enclosed in parentheses).
-In all other contexts,
-Lua adjusts the result list to one element,
-either discarding all values except the first one
-or adding a single <b>nil</b> if there are no values.
-
-
-<p>
-Here are some examples:
-
-<pre>
-     f()                -- adjusted to 0 results
-     g(f(), x)          -- f() is adjusted to 1 result
-     g(x, f())          -- g gets x plus all results from f()
-     a,b,c = f(), x     -- f() is adjusted to 1 result (c gets nil)
-     a,b = ...          -- a gets the first vararg argument, b gets
-                        -- the second (both a and b can get nil if there
-                        -- is no corresponding vararg argument)
-     
-     a,b,c = x, f()     -- f() is adjusted to 2 results
-     a,b,c = f()        -- f() is adjusted to 3 results
-     return f()         -- returns all results from f()
-     return ...         -- returns all received vararg arguments
-     return x,y,f()     -- returns x, y, and all results from f()
-     {f()}              -- creates a list with all results from f()
-     {...}              -- creates a list with all vararg arguments
-     {f(), nil}         -- f() is adjusted to 1 result
-</pre>
-
-<p>
-Any expression enclosed in parentheses always results in only one value.
-Thus,
-<code>(f(x,y,z))</code> is always a single value,
-even if <code>f</code> returns several values.
-(The value of <code>(f(x,y,z))</code> is the first value returned by <code>f</code>
-or <b>nil</b> if <code>f</code> does not return any values.)
-
-
 
 
 
@@ -2252,8 +2195,9 @@ Note that bitwise operators do not do this coercion.
 
 
 <p>
-Nonetheless, it is always a good practice not to rely on these
-implicit coercions, as they are not always applied;
+It is always a good practice not to rely on the
+implicit coercions from strings to numbers,
+as they are not always applied;
 in particular, <code>"1"==1</code> is false and <code>"1"&lt;1</code> raises an error
 (see <a href="#3.4.4">&sect;3.4.4</a>).
 These coercions exist mainly for compatibility and may be removed
@@ -2558,9 +2502,9 @@ The order of the assignments in a constructor is undefined.
 
 <p>
 If the last field in the list has the form <code>exp</code>
-and the expression is a function call or a vararg expression,
+and the expression is a multires expression,
 then all values returned by this expression enter the list consecutively
-(see <a href="#3.4.10">&sect;3.4.10</a>).
+(see <a href="#3.4.12">&sect;3.4.12</a>).
 
 
 <p>
@@ -2624,7 +2568,7 @@ A call of the form <code>return <em>functioncall</em></code> not in the
 scope of a to-be-closed variable is called a <em>tail call</em>.
 Lua implements <em>proper tail calls</em>
 (or <em>proper tail recursion</em>):
-in a tail call,
+In a tail call,
 the called function reuses the stack entry of the calling function.
 Therefore, there is no limit on the number of nested tail calls that
 a program can execute.
@@ -2727,22 +2671,16 @@ initialized with the argument values:
 </pre><p>
 When a Lua function is called,
 it adjusts its list of arguments to
-the length of its list of parameters,
-unless the function is a <em>vararg function</em>,
+the length of its list of parameters (see <a href="#3.4.12">&sect;3.4.12</a>),
+unless the function is a <em>variadic function</em>,
 which is indicated by three dots ('<code>...</code>')
 at the end of its parameter list.
-A vararg function does not adjust its argument list;
+A variadic function does not adjust its argument list;
 instead, it collects all extra arguments and supplies them
 to the function through a <em>vararg expression</em>,
 which is also written as three dots.
 The value of this expression is a list of all actual extra arguments,
-similar to a function with multiple results.
-If a vararg expression is used inside another expression
-or in the middle of a list of expressions,
-then its return list is adjusted to one element.
-If the expression is used as the last element of a list of expressions,
-then no adjustment is made
-(unless that last expression is enclosed in parentheses).
+similar to a function with multiple results (see <a href="#3.4.12">&sect;3.4.12</a>).
 
 
 <p>
@@ -2803,6 +2741,122 @@ is syntactic sugar for
 
 
 
+<h3>3.4.12 &ndash; <a name="3.4.12">Lists of expressions, multiple results,
+and adjustment</a></h3>
+
+<p>
+Both function calls and vararg expressions can result in multiple values.
+These expressions are called <em>multires expressions</em>.
+
+
+<p>
+When a multires expression is used as the last element
+of a list of expressions,
+all results from the expression are added to the
+list of values produced by the list of expressions.
+Note that a single expression
+in a place that expects a list of expressions
+is the last expression in that (singleton) list.
+
+
+<p>
+These are the places where Lua expects a list of expressions:
+
+<ul>
+
+<li>A <b>return</b> statement,
+for instance <code>return e1, e2, e3</code> (see <a href="#3.3.4">&sect;3.3.4</a>).</li>
+
+<li>A table constructor,
+for instance <code>{e1, e2, e3}</code> (see <a href="#3.4.9">&sect;3.4.9</a>).</li>
+
+<li>The arguments of a function call,
+for instance <code>foo(e1, e2, e3)</code> (see <a href="#3.4.10">&sect;3.4.10</a>).</li>
+
+<li>A multiple assignment,
+for instance <code>a , b, c = e1, e2, e3</code> (see <a href="#3.3.3">&sect;3.3.3</a>).</li>
+
+<li>A local declaration,
+for instance <code>local a , b, c = e1, e2, e3</code> (see <a href="#3.3.7">&sect;3.3.7</a>).</li>
+
+<li>The initial values in a generic <b>for</b> loop,
+for instance <code>for k in e1, e2, e3 do ... end</code> (see <a href="#3.3.5">&sect;3.3.5</a>).</li>
+
+</ul><p>
+In the last four cases,
+the list of values from the list of expressions
+must be <em>adjusted</em> to a specific length:
+the number of parameters in a call to a non-variadic function
+(see <a href="#3.4.11">&sect;3.4.11</a>),
+the number of variables in a multiple assignment or
+a local declaration,
+and exactly four values for a generic <b>for</b> loop.
+The <em>adjustment</em> follows these rules:
+If there are more values than needed,
+the extra values are thrown away;
+if there are fewer values than needed,
+the list is extended with <b>nil</b>'s.
+When the list of expressions ends with a multires expression,
+all results from that expression enter the list of values
+before the adjustment.
+
+
+<p>
+When a multires expression is used
+in a list of expressions without being the last element,
+or in a place where the syntax expects a single expression,
+Lua adjusts the result list of that expression to one element.
+As a particular case,
+the syntax expects a single expression inside a parenthesized expression;
+therefore, adding parentheses around a multires expression
+forces it to produce exactly one result.
+
+
+<p>
+We seldom need to use a vararg expression in a place
+where the syntax expects a single expression.
+(Usually it is simpler to add a regular parameter before
+the variadic part and use that parameter.)
+When there is such a need,
+we recommend assigning the vararg expression
+to a single variable and using that variable
+in its place.
+
+
+<p>
+Here are some examples of uses of mutlres expressions.
+In all cases, when the construction needs
+"the n-th result" and there is no such result,
+it uses a <b>nil</b>.
+
+<pre>
+     print(x, f())      -- prints x and all results from f().
+     print(x, (f()))    -- prints x and the first result from f().
+     print(f(), x)      -- prints the first result from f() and x.
+     print(1 + f())     -- prints 1 added to the first result from f().
+     local x = ...      -- x gets the first vararg argument.
+     x,y = ...          -- x gets the first vararg argument,
+                        -- y gets the second vararg argument.
+     x,y,z = w, f()     -- x gets w, y gets the first result from f(),
+                        -- z gets the second result from f().
+     x,y,z = f()        -- x gets the first result from f(),
+                        -- y gets the second result from f(),
+                        -- z gets the third result from f().
+     x,y,z = f(), g()   -- x gets the first result from f(),
+                        -- y gets the first result from g(),
+                        -- z gets the second result from g().
+     x,y,z = (f())      -- x gets the first result from f(), y and z get nil.
+     return f()         -- returns all results from f().
+     return x, ...      -- returns x and all received vararg arguments.
+     return x,y,f()     -- returns x, y, and all results from f().
+     {f()}              -- creates a list with all results from f().
+     {...}              -- creates a list with all vararg arguments.
+     {f(), 5}           -- creates a list with the first result from f() and 5.
+</pre>
+
+
+
+
 
 
 <h2>3.5 &ndash; <a name="3.5">Visibility Rules</a></h2>
@@ -2813,6 +2867,7 @@ Lua is a lexically scoped language.
 The scope of a local variable begins at the first statement after
 its declaration and lasts until the last non-void statement
 of the innermost block that includes the declaration.
+(<em>Void statements</em> are labels and empty statements.)
 Consider the following example:
 
 <pre>
@@ -3071,7 +3126,7 @@ In general,
 Lua's garbage collection can free or move internal memory
 and then invalidate pointers to internal strings.
 To allow a safe use of these pointers,
-The API guarantees that any pointer to a string in a stack index
+the API guarantees that any pointer to a string in a stack index
 is valid while the string value at that index is not removed from the stack.
 (It can be moved to another index, though.)
 When the index is a pseudo-index (referring to an upvalue),
@@ -3537,7 +3592,7 @@ It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newst
          return realloc(ptr, nsize);
      }
 </pre><p>
-Note that Standard&nbsp;C ensures
+Note that ISO&nbsp;C ensures
 that <code>free(NULL)</code> has no effect and that
 <code>realloc(NULL,size)</code> is equivalent to <code>malloc(size)</code>.
 
@@ -3785,8 +3840,36 @@ when called through this function.
 
 
 <p>
-(Exceptionally, this function was introduced in release 5.4.3.
-It is not present in previous 5.4 releases.)
+(This function was introduced in release&nbsp;5.4.3.)
+
+
+
+
+
+<hr><h3><a name="lua_closethread"><code>lua_closethread</code></a></h3><p>
+<span class="apii">[-0, +?, &ndash;]</span>
+<pre>int lua_closethread (lua_State *L, lua_State *from);</pre>
+
+<p>
+Resets a thread, cleaning its call stack and closing all pending
+to-be-closed variables.
+Returns a status code:
+<a href="#pdf-LUA_OK"><code>LUA_OK</code></a> for no errors in the thread
+(either the original error that stopped the thread or
+errors in closing methods),
+or an error status otherwise.
+In case of error,
+leaves the error object on the top of the stack.
+
+
+<p>
+The parameter <code>from</code> represents the coroutine that is resetting <code>L</code>.
+If there is no such coroutine,
+this parameter can be <code>NULL</code>.
+
+
+<p>
+(This function was introduced in release&nbsp;5.4.6.)
 
 
 
@@ -4542,7 +4625,7 @@ Pops a key from the stack,
 and pushes a key&ndash;value pair from the table at the given index,
 the "next" pair after the given key.
 If there are no more elements in the table,
-then <a href="#lua_next"><code>lua_next</code></a> returns 0 and pushes nothing.
+then <a href="#lua_next"><code>lua_next</code></a> returns&nbsp;0 and pushes nothing.
 
 
 <p>
@@ -4985,6 +5068,7 @@ Also returns&nbsp;0 if any of the indices are not valid.
 <p>
 Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw access
 (i.e., without metamethods).
+The value at <code>index</code> must be a table.
 
 
 
@@ -5051,6 +5135,7 @@ For other values, this call returns&nbsp;0.
 <p>
 Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw assignment
 (i.e., without metamethods).
+The value at <code>index</code> must be a table.
 
 
 
@@ -5166,15 +5251,9 @@ and then pops the top element.
 <pre>int lua_resetthread (lua_State *L);</pre>
 
 <p>
-Resets a thread, cleaning its call stack and closing all pending
-to-be-closed variables.
-Returns a status code:
-<a href="#pdf-LUA_OK"><code>LUA_OK</code></a> for no errors in the thread
-(either the original error that stopped the thread or
-errors in closing methods),
-or an error status otherwise.
-In case of error,
-leaves the error object on the top of the stack.
+This function is deprecated;
+it is equivalent to <a href="#lua_closethread"><code>lua_closethread</code></a> with
+<code>from</code> being <code>NULL</code>.
 
 
 
@@ -6033,7 +6112,7 @@ the number of parameters of the function
 </li>
 
 <li><b><code>isvararg</code>: </b>
-true if the function is a vararg function
+true if the function is a variadic function
 (always true for C&nbsp;functions).
 </li>
 
@@ -6773,7 +6852,7 @@ Equivalent to the sequence
 <pre>void luaL_buffsub (luaL_Buffer *B, int n);</pre>
 
 <p>
-Removes <code>n</code> bytes from the the buffer <code>B</code>
+Removes <code>n</code> bytes from the buffer <code>B</code>
 (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
 The buffer must have at least that many bytes.
 
@@ -6968,8 +7047,8 @@ It is defined as the following macro:
 <pre>
      (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0))
 </pre><p>
-It returns <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if there are no errors,
-or an error code in case of errors (see <a href="#4.4.1">&sect;4.4.1</a>).
+It returns&nbsp;0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) if there are no errors,
+or 1 in case of errors.
 
 
 
@@ -6986,8 +7065,8 @@ It is defined as the following macro:
 <pre>
      (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0))
 </pre><p>
-It returns <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if there are no errors,
-or an error code in case of errors (see <a href="#4.4.1">&sect;4.4.1</a>).
+It returns&nbsp;0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) if there are no errors,
+or 1 in case of errors.
 
 
 
@@ -7294,7 +7373,7 @@ with <code>tname</code> in the registry.
 <p>
 Creates a new Lua state.
 It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an
-allocator based on the standard&nbsp;C allocation functions
+allocator based on the ISO&nbsp;C allocation functions
 and then sets a warning function and a panic function (see <a href="#4.4">&sect;4.4</a>)
 that print messages to the standard error output.
 
@@ -7685,9 +7764,7 @@ to start the traceback.
 
 <hr><h3><a name="luaL_typeerror"><code>luaL_typeerror</code></a></h3><p>
 <span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_typeerror (lua_State *L,
-                                      int arg,
-                                      const char *tname);</pre>
+<pre>int luaL_typeerror (lua_State *L, int arg, const char *tname);</pre>
 
 <p>
 Raises a type error for the argument <code>arg</code>
@@ -8708,6 +8785,8 @@ When you require a module <code>modname</code> and
 This variable is only a reference to the real table;
 assignments to this variable do not change the
 table used by <a href="#pdf-require"><code>require</code></a>.
+The real table is stored in the C registry (see <a href="#4.3">&sect;4.3</a>),
+indexed by the key <a name="pdf-LUA_LOADED_TABLE"><code>LUA_LOADED_TABLE</code></a>, a string.
 
 
 
@@ -8745,7 +8824,7 @@ including if necessary a path and an extension.
 
 
 <p>
-This function is not supported by Standard&nbsp;C.
+This functionality is not supported by ISO&nbsp;C.
 As such, it is only available on some platforms
 (Windows, Linux, Mac OS X, Solaris, BSD,
 plus other Unix systems that support the <code>dlfcn</code> standard).
@@ -8799,6 +8878,8 @@ A table to store loaders for specific modules
 This variable is only a reference to the real table;
 assignments to this variable do not change the
 table used by <a href="#pdf-require"><code>require</code></a>.
+The real table is stored in the C registry (see <a href="#4.3">&sect;4.3</a>),
+indexed by the key <a name="pdf-LUA_PRELOAD_TABLE"><code>LUA_PRELOAD_TABLE</code></a>, a string.
 
 
 
@@ -9311,7 +9392,7 @@ according to the format string <code>fmt</code> (see <a href="#6.4.2">&sect;6.4.
 
 
 <p>
-Returns the size of a string resulting from <a href="#pdf-string.pack"><code>string.pack</code></a>
+Returns the length of a string resulting from <a href="#pdf-string.pack"><code>string.pack</code></a>
 with the given format.
 The format string cannot have the variable-length options
 '<code>s</code>' or '<code>z</code>' (see <a href="#6.4.2">&sect;6.4.2</a>).
@@ -10091,9 +10172,9 @@ Returns the arc sine of <code>x</code> (in radians).
 
 
 <p>
-
+ 
 Returns the arc tangent of <code>y/x</code> (in radians),
-but uses the signs of both arguments to find the
+using the signs of both arguments to find the
 quadrant of the result.
 It also handles correctly the case of <code>x</code> being zero.
 
@@ -10953,7 +11034,7 @@ The default value for <code>code</code> is <b>true</b>.
 
 <p>
 If the optional second argument <code>close</code> is true,
-closes the Lua state before exiting.
+the function closes the Lua state before exiting (see <a href="#lua_close"><code>lua_close</code></a>).
 
 
 
@@ -11503,12 +11584,18 @@ The options are:
 <li><b><code>-i</code>: </b> enter interactive mode after running <em>script</em>;</li>
 <li><b><code>-l <em>mod</em></code>: </b> "require" <em>mod</em> and assign the
   result to global <em>mod</em>;</li>
+<li><b><code>-l <em>g=mod</em></code>: </b> "require" <em>mod</em> and assign the
+  result to global <em>g</em>;</li>
 <li><b><code>-v</code>: </b> print version information;</li>
 <li><b><code>-E</code>: </b> ignore environment variables;</li>
 <li><b><code>-W</code>: </b> turn warnings on;</li>
 <li><b><code>--</code>: </b> stop handling options;</li>
 <li><b><code>-</code>: </b> execute <code>stdin</code> as a file and stop handling options.</li>
 </ul><p>
+(The form <code>-l <em>g=mod</em></code> was introduced in release&nbsp;5.4.4.)
+
+
+<p>
 After handling its options, <code>lua</code> runs the given <em>script</em>.
 When called without arguments,
 <code>lua</code> behaves as <code>lua -v -i</code>
@@ -11582,7 +11669,7 @@ If there is a script,
 the script is called with arguments
 <code>arg[1]</code>, &middot;&middot;&middot;, <code>arg[#arg]</code>.
 Like all chunks in Lua,
-the script is compiled as a vararg function.
+the script is compiled as a variadic function.
 
 
 <p>
@@ -11949,10 +12036,10 @@ and LiteralString, see <a href="#3.1">&sect;3.1</a>.)
 
 <P CLASS="footer">
 Last update:
-Thu Jan 13 11:33:16 UTC 2022
+Tue May  2 20:09:38 UTC 2023
 </P>
 <!--
-Last change: revised for Lua 5.4.4
+Last change: revised for Lua 5.4.6
 -->
 
 </body></html>
diff --git a/doc/readme.html b/doc/readme.html
index 8afe38de923b..918ec8ed9378 100644
--- a/doc/readme.html
+++ b/doc/readme.html
@@ -98,9 +98,6 @@ and
 If you don't have the time or the inclination to compile Lua yourself,
 get a binary from
 <A HREF="http://lua-users.org/wiki/LuaBinaries">LuaBinaries</A>.
-Try also
-<A HREF="http://luadist.org/">LuaDist</A>,
-a multi-platform distribution of Lua that includes batteries.
 
 <H3>Building Lua</H3>
 <P>
@@ -110,7 +107,7 @@ Here are the details.
 <OL>
 <LI>
 Open a terminal window and move to
-the top-level directory, which is named <TT>lua-5.4.4</TT>.
+the top-level directory, which is named <TT>lua-5.4.6</TT>.
 The <TT>Makefile</TT> there controls both the build process and the installation process.
 <P>
 <LI>
@@ -121,7 +118,7 @@ The <TT>Makefile</TT> there controls both the build process and the installation
   The platforms currently supported are:
 <P>
 <P CLASS="display">
-   guess aix bsd c89 freebsd generic linux linux-readline macosx mingw posix solaris
+   guess aix bsd c89 freebsd generic ios linux linux-readline macosx mingw posix solaris
 </P>
 <P>
   If your platform is listed, just do "<KBD>make xxx</KBD>", where xxx
@@ -303,7 +300,7 @@ For details, see
 <A HREF="http://www.lua.org/license.html">this</A>.
 
 <BLOCKQUOTE STYLE="padding-bottom: 0em">
-Copyright &copy; 1994&ndash;2022 Lua.org, PUC-Rio.
+Copyright &copy; 1994&ndash;2023 Lua.org, PUC-Rio.
 
 <P>
 Permission is hereby granted, free of charge, to any person obtaining a copy
@@ -330,10 +327,10 @@ THE SOFTWARE.
 
 <P CLASS="footer">
 Last update:
-Mon Jan  3 09:54:18 UTC 2022
+Tue May  2 20:08:55 UTC 2023
 </P>
 <!--
-Last change: revised for Lua 5.4.4
+Last change: revised for Lua 5.4.6
 -->
 
 </BODY>
diff --git a/src/Makefile b/src/Makefile
index 1907381fef0a..b7711963bccd 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -30,7 +30,7 @@ CMCFLAGS=
 
 # == END OF USER SETTINGS -- NO NEED TO CHANGE ANYTHING BELOW THIS LINE =======
 
-PLATS= guess aix bsd c89 freebsd generic linux linux-readline macosx mingw posix solaris
+PLATS= guess aix bsd c89 freebsd generic ios linux linux-readline macosx mingw posix solaris
 
 LUA_A=	liblua.a
 CORE_O=	lapi.o lcode.o lctype.o ldebug.o ldo.o ldump.o lfunc.o lgc.o llex.o lmem.o lobject.o lopcodes.o lparser.o lstate.o lstring.o ltable.o ltm.o lundump.o lvm.o lzio.o
@@ -117,6 +117,9 @@ FreeBSD NetBSD OpenBSD freebsd:
 
 generic: $(ALL)
 
+ios:
+	$(MAKE) $(ALL) SYSCFLAGS="-DLUA_USE_IOS"
+
 Linux linux:	linux-noreadline
 
 linux-noreadline:
diff --git a/src/lapi.c b/src/lapi.c
index 5ee65792d277..34e64af1428c 100644
--- a/src/lapi.c
+++ b/src/lapi.c
@@ -60,27 +60,28 @@ const char lua_ident[] =
 static TValue *index2value (lua_State *L, int idx) {
   CallInfo *ci = L->ci;
   if (idx > 0) {
-    StkId o = ci->func + idx;
-    api_check(L, idx <= L->ci->top - (ci->func + 1), "unacceptable index");
-    if (o >= L->top) return &G(L)->nilvalue;
+    StkId o = ci->func.p + idx;
+    api_check(L, idx <= ci->top.p - (ci->func.p + 1), "unacceptable index");
+    if (o >= L->top.p) return &G(L)->nilvalue;
     else return s2v(o);
   }
   else if (!ispseudo(idx)) {  /* negative index */
-    api_check(L, idx != 0 && -idx <= L->top - (ci->func + 1), "invalid index");
-    return s2v(L->top + idx);
+    api_check(L, idx != 0 && -idx <= L->top.p - (ci->func.p + 1),
+                 "invalid index");
+    return s2v(L->top.p + idx);
   }
   else if (idx == LUA_REGISTRYINDEX)
     return &G(L)->l_registry;
   else {  /* upvalues */
     idx = LUA_REGISTRYINDEX - idx;
     api_check(L, idx <= MAXUPVAL + 1, "upvalue index too large");
-    if (ttisCclosure(s2v(ci->func))) {  /* C closure? */
-      CClosure *func = clCvalue(s2v(ci->func));
+    if (ttisCclosure(s2v(ci->func.p))) {  /* C closure? */
+      CClosure *func = clCvalue(s2v(ci->func.p));
       return (idx <= func->nupvalues) ? &func->upvalue[idx-1]
                                       : &G(L)->nilvalue;
     }
     else {  /* light C function or Lua function (through a hook)?) */
-      api_check(L, ttislcf(s2v(ci->func)), "caller not a C function");
+      api_check(L, ttislcf(s2v(ci->func.p)), "caller not a C function");
       return &G(L)->nilvalue;  /* no upvalues */
     }
   }
@@ -94,14 +95,15 @@ static TValue *index2value (lua_State *L, int idx) {
 l_sinline StkId index2stack (lua_State *L, int idx) {
   CallInfo *ci = L->ci;
   if (idx > 0) {
-    StkId o = ci->func + idx;
-    api_check(L, o < L->top, "invalid index");
+    StkId o = ci->func.p + idx;
+    api_check(L, o < L->top.p, "invalid index");
     return o;
   }
   else {    /* non-positive index */
-    api_check(L, idx != 0 && -idx <= L->top - (ci->func + 1), "invalid index");
+    api_check(L, idx != 0 && -idx <= L->top.p - (ci->func.p + 1),
+                 "invalid index");
     api_check(L, !ispseudo(idx), "invalid index");
-    return L->top + idx;
+    return L->top.p + idx;
   }
 }
 
@@ -112,17 +114,12 @@ LUA_API int lua_checkstack (lua_State *L, int n) {
   lua_lock(L);
   ci = L->ci;
   api_check(L, n >= 0, "negative 'n'");
-  if (L->stack_last - L->top > n)  /* stack large enough? */
+  if (L->stack_last.p - L->top.p > n)  /* stack large enough? */
     res = 1;  /* yes; check is OK */
-  else {  /* no; need to grow stack */
-    int inuse = cast_int(L->top - L->stack) + EXTRA_STACK;
-    if (inuse > LUAI_MAXSTACK - n)  /* can grow without overflow? */
-      res = 0;  /* no */
-    else  /* try to grow stack */
-      res = luaD_growstack(L, n, 0);
-  }
-  if (res && ci->top < L->top + n)
-    ci->top = L->top + n;  /* adjust frame top */
+  else  /* need to grow stack */
+    res = luaD_growstack(L, n, 0);
+  if (res && ci->top.p < L->top.p + n)
+    ci->top.p = L->top.p + n;  /* adjust frame top */
   lua_unlock(L);
   return res;
 }
@@ -134,11 +131,11 @@ LUA_API void lua_xmove (lua_State *from, lua_State *to, int n) {
   lua_lock(to);
   api_checknelems(from, n);
   api_check(from, G(from) == G(to), "moving among independent states");
-  api_check(from, to->ci->top - to->top >= n, "stack overflow");
-  from->top -= n;
+  api_check(from, to->ci->top.p - to->top.p >= n, "stack overflow");
+  from->top.p -= n;
   for (i = 0; i < n; i++) {
-    setobjs2s(to, to->top, from->top + i);
-    to->top++;  /* stack already checked by previous 'api_check' */
+    setobjs2s(to, to->top.p, from->top.p + i);
+    to->top.p++;  /* stack already checked by previous 'api_check' */
   }
   lua_unlock(to);
 }
@@ -172,12 +169,12 @@ LUA_API lua_Number lua_version (lua_State *L) {
 LUA_API int lua_absindex (lua_State *L, int idx) {
   return (idx > 0 || ispseudo(idx))
          ? idx
-         : cast_int(L->top - L->ci->func) + idx;
+         : cast_int(L->top.p - L->ci->func.p) + idx;
 }
 
 
 LUA_API int lua_gettop (lua_State *L) {
-  return cast_int(L->top - (L->ci->func + 1));
+  return cast_int(L->top.p - (L->ci->func.p + 1));
 }
 
 
@@ -187,24 +184,24 @@ LUA_API void lua_settop (lua_State *L, int idx) {
   ptrdiff_t diff;  /* difference for new top */
   lua_lock(L);
   ci = L->ci;
-  func = ci->func;
+  func = ci->func.p;
   if (idx >= 0) {
-    api_check(L, idx <= ci->top - (func + 1), "new top too large");
-    diff = ((func + 1) + idx) - L->top;
+    api_check(L, idx <= ci->top.p - (func + 1), "new top too large");
+    diff = ((func + 1) + idx) - L->top.p;
     for (; diff > 0; diff--)
-      setnilvalue(s2v(L->top++));  /* clear new slots */
+      setnilvalue(s2v(L->top.p++));  /* clear new slots */
   }
   else {
-    api_check(L, -(idx+1) <= (L->top - (func + 1)), "invalid new top");
+    api_check(L, -(idx+1) <= (L->top.p - (func + 1)), "invalid new top");
     diff = idx + 1;  /* will "subtract" index (as it is negative) */
   }
-  api_check(L, L->tbclist < L->top, "previous pop of an unclosed slot");
-  newtop = L->top + diff;
-  if (diff < 0 && L->tbclist >= newtop) {
+  api_check(L, L->tbclist.p < L->top.p, "previous pop of an unclosed slot");
+  newtop = L->top.p + diff;
+  if (diff < 0 && L->tbclist.p >= newtop) {
     lua_assert(hastocloseCfunc(ci->nresults));
-    luaF_close(L, newtop, CLOSEKTOP, 0);
+    newtop = luaF_close(L, newtop, CLOSEKTOP, 0);
   }
-  L->top = newtop;  /* correct top only after closing any upvalue */
+  L->top.p = newtop;  /* correct top only after closing any upvalue */
   lua_unlock(L);
 }
 
@@ -213,10 +210,9 @@ LUA_API void lua_closeslot (lua_State *L, int idx) {
   StkId level;
   lua_lock(L);
   level = index2stack(L, idx);
-  api_check(L, hastocloseCfunc(L->ci->nresults) && L->tbclist == level,
+  api_check(L, hastocloseCfunc(L->ci->nresults) && L->tbclist.p == level,
      "no variable to close at given level");
-  luaF_close(L, level, CLOSEKTOP, 0);
-  level = index2stack(L, idx);  /* stack may be moved */
+  level = luaF_close(L, level, CLOSEKTOP, 0);
   setnilvalue(s2v(level));
   lua_unlock(L);
 }
@@ -245,7 +241,7 @@ l_sinline void reverse (lua_State *L, StkId from, StkId to) {
 LUA_API void lua_rotate (lua_State *L, int idx, int n) {
   StkId p, t, m;
   lua_lock(L);
-  t = L->top - 1;  /* end of stack segment being rotated */
+  t = L->top.p - 1;  /* end of stack segment being rotated */
   p = index2stack(L, idx);  /* start of segment */
   api_check(L, (n >= 0 ? n : -n) <= (t - p + 1), "invalid 'n'");
   m = (n >= 0 ? t - n : p - n - 1);  /* end of prefix */
@@ -264,7 +260,7 @@ LUA_API void lua_copy (lua_State *L, int fromidx, int toidx) {
   api_check(L, isvalid(L, to), "invalid index");
   setobj(L, to, fr);
   if (isupvalue(toidx))  /* function upvalue? */
-    luaC_barrier(L, clCvalue(s2v(L->ci->func)), fr);
+    luaC_barrier(L, clCvalue(s2v(L->ci->func.p)), fr);
   /* LUA_REGISTRYINDEX does not need gc barrier
      (collector revisits it before finishing collection) */
   lua_unlock(L);
@@ -273,7 +269,7 @@ LUA_API void lua_copy (lua_State *L, int fromidx, int toidx) {
 
 LUA_API void lua_pushvalue (lua_State *L, int idx) {
   lua_lock(L);
-  setobj2s(L, L->top, index2value(L, idx));
+  setobj2s(L, L->top.p, index2value(L, idx));
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -342,12 +338,12 @@ LUA_API void lua_arith (lua_State *L, int op) {
     api_checknelems(L, 2);  /* all other operations expect two operands */
   else {  /* for unary operations, add fake 2nd operand */
     api_checknelems(L, 1);
-    setobjs2s(L, L->top, L->top - 1);
+    setobjs2s(L, L->top.p, L->top.p - 1);
     api_incr_top(L);
   }
   /* first operand at top - 2, second at top - 1; result go to top - 2 */
-  luaO_arith(L, op, s2v(L->top - 2), s2v(L->top - 1), L->top - 2);
-  L->top--;  /* remove second operand */
+  luaO_arith(L, op, s2v(L->top.p - 2), s2v(L->top.p - 1), L->top.p - 2);
+  L->top.p--;  /* remove second operand */
   lua_unlock(L);
 }
 
@@ -373,7 +369,7 @@ LUA_API int lua_compare (lua_State *L, int index1, int index2, int op) {
 
 
 LUA_API size_t lua_stringtonumber (lua_State *L, const char *s) {
-  size_t sz = luaO_str2num(s, s2v(L->top));
+  size_t sz = luaO_str2num(s, s2v(L->top.p));
   if (sz != 0)
     api_incr_top(L);
   return sz;
@@ -500,7 +496,7 @@ LUA_API const void *lua_topointer (lua_State *L, int idx) {
 
 LUA_API void lua_pushnil (lua_State *L) {
   lua_lock(L);
-  setnilvalue(s2v(L->top));
+  setnilvalue(s2v(L->top.p));
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -508,7 +504,7 @@ LUA_API void lua_pushnil (lua_State *L) {
 
 LUA_API void lua_pushnumber (lua_State *L, lua_Number n) {
   lua_lock(L);
-  setfltvalue(s2v(L->top), n);
+  setfltvalue(s2v(L->top.p), n);
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -516,7 +512,7 @@ LUA_API void lua_pushnumber (lua_State *L, lua_Number n) {
 
 LUA_API void lua_pushinteger (lua_State *L, lua_Integer n) {
   lua_lock(L);
-  setivalue(s2v(L->top), n);
+  setivalue(s2v(L->top.p), n);
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -531,7 +527,7 @@ LUA_API const char *lua_pushlstring (lua_State *L, const char *s, size_t len) {
   TString *ts;
   lua_lock(L);
   ts = (len == 0) ? luaS_new(L, "") : luaS_newlstr(L, s, len);
-  setsvalue2s(L, L->top, ts);
+  setsvalue2s(L, L->top.p, ts);
   api_incr_top(L);
   luaC_checkGC(L);
   lua_unlock(L);
@@ -542,11 +538,11 @@ LUA_API const char *lua_pushlstring (lua_State *L, const char *s, size_t len) {
 LUA_API const char *lua_pushstring (lua_State *L, const char *s) {
   lua_lock(L);
   if (s == NULL)
-    setnilvalue(s2v(L->top));
+    setnilvalue(s2v(L->top.p));
   else {
     TString *ts;
     ts = luaS_new(L, s);
-    setsvalue2s(L, L->top, ts);
+    setsvalue2s(L, L->top.p, ts);
     s = getstr(ts);  /* internal copy's address */
   }
   api_incr_top(L);
@@ -583,7 +579,7 @@ LUA_API const char *lua_pushfstring (lua_State *L, const char *fmt, ...) {
 LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
   lua_lock(L);
   if (n == 0) {
-    setfvalue(s2v(L->top), fn);
+    setfvalue(s2v(L->top.p), fn);
     api_incr_top(L);
   }
   else {
@@ -592,13 +588,13 @@ LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
     api_check(L, n <= MAXUPVAL, "upvalue index too large");
     cl = luaF_newCclosure(L, n);
     cl->f = fn;
-    L->top -= n;
+    L->top.p -= n;
     while (n--) {
-      setobj2n(L, &cl->upvalue[n], s2v(L->top + n));
+      setobj2n(L, &cl->upvalue[n], s2v(L->top.p + n));
       /* does not need barrier because closure is white */
       lua_assert(iswhite(cl));
     }
-    setclCvalue(L, s2v(L->top), cl);
+    setclCvalue(L, s2v(L->top.p), cl);
     api_incr_top(L);
     luaC_checkGC(L);
   }
@@ -609,9 +605,9 @@ LUA_API void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n) {
 LUA_API void lua_pushboolean (lua_State *L, int b) {
   lua_lock(L);
   if (b)
-    setbtvalue(s2v(L->top));
+    setbtvalue(s2v(L->top.p));
   else
-    setbfvalue(s2v(L->top));
+    setbfvalue(s2v(L->top.p));
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -619,7 +615,7 @@ LUA_API void lua_pushboolean (lua_State *L, int b) {
 
 LUA_API void lua_pushlightuserdata (lua_State *L, void *p) {
   lua_lock(L);
-  setpvalue(s2v(L->top), p);
+  setpvalue(s2v(L->top.p), p);
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -627,7 +623,7 @@ LUA_API void lua_pushlightuserdata (lua_State *L, void *p) {
 
 LUA_API int lua_pushthread (lua_State *L) {
   lua_lock(L);
-  setthvalue(L, s2v(L->top), L);
+  setthvalue(L, s2v(L->top.p), L);
   api_incr_top(L);
   lua_unlock(L);
   return (G(L)->mainthread == L);
@@ -644,16 +640,16 @@ l_sinline int auxgetstr (lua_State *L, const TValue *t, const char *k) {
   const TValue *slot;
   TString *str = luaS_new(L, k);
   if (luaV_fastget(L, t, str, slot, luaH_getstr)) {
-    setobj2s(L, L->top, slot);
+    setobj2s(L, L->top.p, slot);
     api_incr_top(L);
   }
   else {
-    setsvalue2s(L, L->top, str);
+    setsvalue2s(L, L->top.p, str);
     api_incr_top(L);
-    luaV_finishget(L, t, s2v(L->top - 1), L->top - 1, slot);
+    luaV_finishget(L, t, s2v(L->top.p - 1), L->top.p - 1, slot);
   }
   lua_unlock(L);
-  return ttype(s2v(L->top - 1));
+  return ttype(s2v(L->top.p - 1));
 }
 
 
@@ -680,13 +676,13 @@ LUA_API int lua_gettable (lua_State *L, int idx) {
   TValue *t;
   lua_lock(L);
   t = index2value(L, idx);
-  if (luaV_fastget(L, t, s2v(L->top - 1), slot, luaH_get)) {
-    setobj2s(L, L->top - 1, slot);
+  if (luaV_fastget(L, t, s2v(L->top.p - 1), slot, luaH_get)) {
+    setobj2s(L, L->top.p - 1, slot);
   }
   else
-    luaV_finishget(L, t, s2v(L->top - 1), L->top - 1, slot);
+    luaV_finishget(L, t, s2v(L->top.p - 1), L->top.p - 1, slot);
   lua_unlock(L);
-  return ttype(s2v(L->top - 1));
+  return ttype(s2v(L->top.p - 1));
 }
 
 
@@ -702,27 +698,27 @@ LUA_API int lua_geti (lua_State *L, int idx, lua_Integer n) {
   lua_lock(L);
   t = index2value(L, idx);
   if (luaV_fastgeti(L, t, n, slot)) {
-    setobj2s(L, L->top, slot);
+    setobj2s(L, L->top.p, slot);
   }
   else {
     TValue aux;
     setivalue(&aux, n);
-    luaV_finishget(L, t, &aux, L->top, slot);
+    luaV_finishget(L, t, &aux, L->top.p, slot);
   }
   api_incr_top(L);
   lua_unlock(L);
-  return ttype(s2v(L->top - 1));
+  return ttype(s2v(L->top.p - 1));
 }
 
 
 l_sinline int finishrawget (lua_State *L, const TValue *val) {
   if (isempty(val))  /* avoid copying empty items to the stack */
-    setnilvalue(s2v(L->top));
+    setnilvalue(s2v(L->top.p));
   else
-    setobj2s(L, L->top, val);
+    setobj2s(L, L->top.p, val);
   api_incr_top(L);
   lua_unlock(L);
-  return ttype(s2v(L->top - 1));
+  return ttype(s2v(L->top.p - 1));
 }
 
 
@@ -739,8 +735,8 @@ LUA_API int lua_rawget (lua_State *L, int idx) {
   lua_lock(L);
   api_checknelems(L, 1);
   t = gettable(L, idx);
-  val = luaH_get(t, s2v(L->top - 1));
-  L->top--;  /* remove key */
+  val = luaH_get(t, s2v(L->top.p - 1));
+  L->top.p--;  /* remove key */
   return finishrawget(L, val);
 }
 
@@ -767,7 +763,7 @@ LUA_API void lua_createtable (lua_State *L, int narray, int nrec) {
   Table *t;
   lua_lock(L);
   t = luaH_new(L);
-  sethvalue2s(L, L->top, t);
+  sethvalue2s(L, L->top.p, t);
   api_incr_top(L);
   if (narray > 0 || nrec > 0)
     luaH_resize(L, t, narray, nrec);
@@ -794,7 +790,7 @@ LUA_API int lua_getmetatable (lua_State *L, int objindex) {
       break;
   }
   if (mt != NULL) {
-    sethvalue2s(L, L->top, mt);
+    sethvalue2s(L, L->top.p, mt);
     api_incr_top(L);
     res = 1;
   }
@@ -810,12 +806,12 @@ LUA_API int lua_getiuservalue (lua_State *L, int idx, int n) {
   o = index2value(L, idx);
   api_check(L, ttisfulluserdata(o), "full userdata expected");
   if (n <= 0 || n > uvalue(o)->nuvalue) {
-    setnilvalue(s2v(L->top));
+    setnilvalue(s2v(L->top.p));
     t = LUA_TNONE;
   }
   else {
-    setobj2s(L, L->top, &uvalue(o)->uv[n - 1].uv);
-    t = ttype(s2v(L->top));
+    setobj2s(L, L->top.p, &uvalue(o)->uv[n - 1].uv);
+    t = ttype(s2v(L->top.p));
   }
   api_incr_top(L);
   lua_unlock(L);
@@ -835,14 +831,14 @@ static void auxsetstr (lua_State *L, const TValue *t, const char *k) {
   TString *str = luaS_new(L, k);
   api_checknelems(L, 1);
   if (luaV_fastget(L, t, str, slot, luaH_getstr)) {
-    luaV_finishfastset(L, t, slot, s2v(L->top - 1));
-    L->top--;  /* pop value */
+    luaV_finishfastset(L, t, slot, s2v(L->top.p - 1));
+    L->top.p--;  /* pop value */
   }
   else {
-    setsvalue2s(L, L->top, str);  /* push 'str' (to make it a TValue) */
+    setsvalue2s(L, L->top.p, str);  /* push 'str' (to make it a TValue) */
     api_incr_top(L);
-    luaV_finishset(L, t, s2v(L->top - 1), s2v(L->top - 2), slot);
-    L->top -= 2;  /* pop value and key */
+    luaV_finishset(L, t, s2v(L->top.p - 1), s2v(L->top.p - 2), slot);
+    L->top.p -= 2;  /* pop value and key */
   }
   lua_unlock(L);  /* lock done by caller */
 }
@@ -862,12 +858,12 @@ LUA_API void lua_settable (lua_State *L, int idx) {
   lua_lock(L);
   api_checknelems(L, 2);
   t = index2value(L, idx);
-  if (luaV_fastget(L, t, s2v(L->top - 2), slot, luaH_get)) {
-    luaV_finishfastset(L, t, slot, s2v(L->top - 1));
+  if (luaV_fastget(L, t, s2v(L->top.p - 2), slot, luaH_get)) {
+    luaV_finishfastset(L, t, slot, s2v(L->top.p - 1));
   }
   else
-    luaV_finishset(L, t, s2v(L->top - 2), s2v(L->top - 1), slot);
-  L->top -= 2;  /* pop index and value */
+    luaV_finishset(L, t, s2v(L->top.p - 2), s2v(L->top.p - 1), slot);
+  L->top.p -= 2;  /* pop index and value */
   lua_unlock(L);
 }
 
@@ -885,14 +881,14 @@ LUA_API void lua_seti (lua_State *L, int idx, lua_Integer n) {
   api_checknelems(L, 1);
   t = index2value(L, idx);
   if (luaV_fastgeti(L, t, n, slot)) {
-    luaV_finishfastset(L, t, slot, s2v(L->top - 1));
+    luaV_finishfastset(L, t, slot, s2v(L->top.p - 1));
   }
   else {
     TValue aux;
     setivalue(&aux, n);
-    luaV_finishset(L, t, &aux, s2v(L->top - 1), slot);
+    luaV_finishset(L, t, &aux, s2v(L->top.p - 1), slot);
   }
-  L->top--;  /* pop value */
+  L->top.p--;  /* pop value */
   lua_unlock(L);
 }
 
@@ -902,16 +898,16 @@ static void aux_rawset (lua_State *L, int idx, TValue *key, int n) {
   lua_lock(L);
   api_checknelems(L, n);
   t = gettable(L, idx);
-  luaH_set(L, t, key, s2v(L->top - 1));
+  luaH_set(L, t, key, s2v(L->top.p - 1));
   invalidateTMcache(t);
-  luaC_barrierback(L, obj2gco(t), s2v(L->top - 1));
-  L->top -= n;
+  luaC_barrierback(L, obj2gco(t), s2v(L->top.p - 1));
+  L->top.p -= n;
   lua_unlock(L);
 }
 
 
 LUA_API void lua_rawset (lua_State *L, int idx) {
-  aux_rawset(L, idx, s2v(L->top - 2), 2);
+  aux_rawset(L, idx, s2v(L->top.p - 2), 2);
 }
 
 
@@ -927,9 +923,9 @@ LUA_API void lua_rawseti (lua_State *L, int idx, lua_Integer n) {
   lua_lock(L);
   api_checknelems(L, 1);
   t = gettable(L, idx);
-  luaH_setint(L, t, n, s2v(L->top - 1));
-  luaC_barrierback(L, obj2gco(t), s2v(L->top - 1));
-  L->top--;
+  luaH_setint(L, t, n, s2v(L->top.p - 1));
+  luaC_barrierback(L, obj2gco(t), s2v(L->top.p - 1));
+  L->top.p--;
   lua_unlock(L);
 }
 
@@ -940,11 +936,11 @@ LUA_API int lua_setmetatable (lua_State *L, int objindex) {
   lua_lock(L);
   api_checknelems(L, 1);
   obj = index2value(L, objindex);
-  if (ttisnil(s2v(L->top - 1)))
+  if (ttisnil(s2v(L->top.p - 1)))
     mt = NULL;
   else {
-    api_check(L, ttistable(s2v(L->top - 1)), "table expected");
-    mt = hvalue(s2v(L->top - 1));
+    api_check(L, ttistable(s2v(L->top.p - 1)), "table expected");
+    mt = hvalue(s2v(L->top.p - 1));
   }
   switch (ttype(obj)) {
     case LUA_TTABLE: {
@@ -968,7 +964,7 @@ LUA_API int lua_setmetatable (lua_State *L, int objindex) {
       break;
     }
   }
-  L->top--;
+  L->top.p--;
   lua_unlock(L);
   return 1;
 }
@@ -984,11 +980,11 @@ LUA_API int lua_setiuservalue (lua_State *L, int idx, int n) {
   if (!(cast_uint(n) - 1u < cast_uint(uvalue(o)->nuvalue)))
     res = 0;  /* 'n' not in [1, uvalue(o)->nuvalue] */
   else {
-    setobj(L, &uvalue(o)->uv[n - 1].uv, s2v(L->top - 1));
-    luaC_barrierback(L, gcvalue(o), s2v(L->top - 1));
+    setobj(L, &uvalue(o)->uv[n - 1].uv, s2v(L->top.p - 1));
+    luaC_barrierback(L, gcvalue(o), s2v(L->top.p - 1));
     res = 1;
   }
-  L->top--;
+  L->top.p--;
   lua_unlock(L);
   return res;
 }
@@ -1000,7 +996,8 @@ LUA_API int lua_setiuservalue (lua_State *L, int idx, int n) {
 
 
 #define checkresults(L,na,nr) \
-     api_check(L, (nr) == LUA_MULTRET || (L->ci->top - L->top >= (nr) - (na)), \
+     api_check(L, (nr) == LUA_MULTRET \
+               || (L->ci->top.p - L->top.p >= (nr) - (na)), \
 	"results from function overflow current stack size")
 
 
@@ -1013,7 +1010,7 @@ LUA_API void lua_callk (lua_State *L, int nargs, int nresults,
   api_checknelems(L, nargs+1);
   api_check(L, L->status == LUA_OK, "cannot do calls on non-normal thread");
   checkresults(L, nargs, nresults);
-  func = L->top - (nargs+1);
+  func = L->top.p - (nargs+1);
   if (k != NULL && yieldable(L)) {  /* need to prepare continuation? */
     L->ci->u.c.k = k;  /* save continuation */
     L->ci->u.c.ctx = ctx;  /* save context */
@@ -1061,7 +1058,7 @@ LUA_API int lua_pcallk (lua_State *L, int nargs, int nresults, int errfunc,
     api_check(L, ttisfunction(s2v(o)), "error handler must be a function");
     func = savestack(L, o);
   }
-  c.func = L->top - (nargs+1);  /* function to be called */
+  c.func = L->top.p - (nargs+1);  /* function to be called */
   if (k == NULL || !yieldable(L)) {  /* no continuation or no yieldable? */
     c.nresults = nresults;  /* do a 'conventional' protected call */
     status = luaD_pcall(L, f_call, &c, savestack(L, c.func), func);
@@ -1096,12 +1093,12 @@ LUA_API int lua_load (lua_State *L, lua_Reader reader, void *data,
   luaZ_init(L, &z, reader, data);
   status = luaD_protectedparser(L, &z, chunkname, mode);
   if (status == LUA_OK) {  /* no errors? */
-    LClosure *f = clLvalue(s2v(L->top - 1));  /* get newly created function */
+    LClosure *f = clLvalue(s2v(L->top.p - 1));  /* get new function */
     if (f->nupvalues >= 1) {  /* does it have an upvalue? */
       /* get global table from registry */
       const TValue *gt = getGtable(L);
       /* set global table as 1st upvalue of 'f' (may be LUA_ENV) */
-      setobj(L, f->upvals[0]->v, gt);
+      setobj(L, f->upvals[0]->v.p, gt);
       luaC_barrier(L, f->upvals[0], gt);
     }
   }
@@ -1115,7 +1112,7 @@ LUA_API int lua_dump (lua_State *L, lua_Writer writer, void *data, int strip) {
   TValue *o;
   lua_lock(L);
   api_checknelems(L, 1);
-  o = s2v(L->top - 1);
+  o = s2v(L->top.p - 1);
   if (isLfunction(o))
     status = luaU_dump(L, getproto(o), writer, data, strip);
   else
@@ -1241,7 +1238,7 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
 LUA_API int lua_error (lua_State *L) {
   TValue *errobj;
   lua_lock(L);
-  errobj = s2v(L->top - 1);
+  errobj = s2v(L->top.p - 1);
   api_checknelems(L, 1);
   /* error object is the memory error message? */
   if (ttisshrstring(errobj) && eqshrstr(tsvalue(errobj), G(L)->memerrmsg))
@@ -1259,12 +1256,12 @@ LUA_API int lua_next (lua_State *L, int idx) {
   lua_lock(L);
   api_checknelems(L, 1);
   t = gettable(L, idx);
-  more = luaH_next(L, t, L->top - 1);
+  more = luaH_next(L, t, L->top.p - 1);
   if (more) {
     api_incr_top(L);
   }
   else  /* no more elements */
-    L->top -= 1;  /* remove key */
+    L->top.p -= 1;  /* remove key */
   lua_unlock(L);
   return more;
 }
@@ -1276,7 +1273,7 @@ LUA_API void lua_toclose (lua_State *L, int idx) {
   lua_lock(L);
   o = index2stack(L, idx);
   nresults = L->ci->nresults;
-  api_check(L, L->tbclist < o, "given index below or equal a marked one");
+  api_check(L, L->tbclist.p < o, "given index below or equal a marked one");
   luaF_newtbcupval(L, o);  /* create new to-be-closed upvalue */
   if (!hastocloseCfunc(nresults))  /* function not marked yet? */
     L->ci->nresults = codeNresults(nresults);  /* mark it */
@@ -1291,7 +1288,7 @@ LUA_API void lua_concat (lua_State *L, int n) {
   if (n > 0)
     luaV_concat(L, n);
   else {  /* nothing to concatenate */
-    setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));  /* push empty string */
+    setsvalue2s(L, L->top.p, luaS_newlstr(L, "", 0));  /* push empty string */
     api_incr_top(L);
   }
   luaC_checkGC(L);
@@ -1303,7 +1300,7 @@ LUA_API void lua_len (lua_State *L, int idx) {
   TValue *t;
   lua_lock(L);
   t = index2value(L, idx);
-  luaV_objlen(L, L->top, t);
+  luaV_objlen(L, L->top.p, t);
   api_incr_top(L);
   lua_unlock(L);
 }
@@ -1348,7 +1345,7 @@ LUA_API void *lua_newuserdatauv (lua_State *L, size_t size, int nuvalue) {
   lua_lock(L);
   api_check(L, 0 <= nuvalue && nuvalue < USHRT_MAX, "invalid value");
   u = luaS_newudata(L, size, nuvalue);
-  setuvalue(L, s2v(L->top), u);
+  setuvalue(L, s2v(L->top.p), u);
   api_incr_top(L);
   luaC_checkGC(L);
   lua_unlock(L);
@@ -1374,7 +1371,7 @@ static const char *aux_upvalue (TValue *fi, int n, TValue **val,
       Proto *p = f->p;
       if (!(cast_uint(n) - 1u  < cast_uint(p->sizeupvalues)))
         return NULL;  /* 'n' not in [1, p->sizeupvalues] */
-      *val = f->upvals[n-1]->v;
+      *val = f->upvals[n-1]->v.p;
       if (owner) *owner = obj2gco(f->upvals[n - 1]);
       name = p->upvalues[n-1].name;
       return (name == NULL) ? "(no name)" : getstr(name);
@@ -1390,7 +1387,7 @@ LUA_API const char *lua_getupvalue (lua_State *L, int funcindex, int n) {
   lua_lock(L);
   name = aux_upvalue(index2value(L, funcindex), n, &val, NULL);
   if (name) {
-    setobj2s(L, L->top, val);
+    setobj2s(L, L->top.p, val);
     api_incr_top(L);
   }
   lua_unlock(L);
@@ -1408,8 +1405,8 @@ LUA_API const char *lua_setupvalue (lua_State *L, int funcindex, int n) {
   api_checknelems(L, 1);
   name = aux_upvalue(fi, n, &val, &owner);
   if (name) {
-    L->top--;
-    setobj(L, val, s2v(L->top));
+    L->top.p--;
+    setobj(L, val, s2v(L->top.p));
     luaC_barrier(L, owner, val);
   }
   lua_unlock(L);
diff --git a/src/lapi.h b/src/lapi.h
index 9e99cc44824d..a742427cdc79 100644
--- a/src/lapi.h
+++ b/src/lapi.h
@@ -12,23 +12,26 @@
 #include "lstate.h"
 
 
-/* Increments 'L->top', checking for stack overflows */
-#define api_incr_top(L)   {L->top++; api_check(L, L->top <= L->ci->top, \
-				"stack overflow");}
+/* Increments 'L->top.p', checking for stack overflows */
+#define api_incr_top(L)	{L->top.p++; \
+			 api_check(L, L->top.p <= L->ci->top.p, \
+					"stack overflow");}
 
 
 /*
 ** If a call returns too many multiple returns, the callee may not have
 ** stack space to accommodate all results. In this case, this macro
-** increases its stack space ('L->ci->top').
+** increases its stack space ('L->ci->top.p').
 */
 #define adjustresults(L,nres) \
-    { if ((nres) <= LUA_MULTRET && L->ci->top < L->top) L->ci->top = L->top; }
+    { if ((nres) <= LUA_MULTRET && L->ci->top.p < L->top.p) \
+	L->ci->top.p = L->top.p; }
 
 
 /* Ensure the stack has at least 'n' elements */
-#define api_checknelems(L,n)	api_check(L, (n) < (L->top - L->ci->func), \
-				  "not enough elements in the stack")
+#define api_checknelems(L,n) \
+	api_check(L, (n) < (L->top.p - L->ci->func.p), \
+			  "not enough elements in the stack")
 
 
 /*
diff --git a/src/lauxlib.c b/src/lauxlib.c
index 8ed1da1122fc..4ca6c6548899 100644
--- a/src/lauxlib.c
+++ b/src/lauxlib.c
@@ -526,13 +526,14 @@ static void newbox (lua_State *L) {
 
 /*
 ** Compute new size for buffer 'B', enough to accommodate extra 'sz'
-** bytes.
+** bytes. (The test for "not big enough" also gets the case when the
+** computation of 'newsize' overflows.)
 */
 static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
-  size_t newsize = B->size * 2;  /* double buffer size */
+  size_t newsize = (B->size / 2) * 3;  /* buffer size * 1.5 */
   if (l_unlikely(MAX_SIZET - sz < B->n))  /* overflow in (B->n + sz)? */
     return luaL_error(B->L, "buffer too large");
-  if (newsize < B->n + sz)  /* double is not big enough? */
+  if (newsize < B->n + sz)  /* not big enough? */
     newsize = B->n + sz;
   return newsize;
 }
@@ -611,7 +612,7 @@ LUALIB_API void luaL_pushresultsize (luaL_Buffer *B, size_t sz) {
 ** box (if existent) is not on the top of the stack. So, instead of
 ** calling 'luaL_addlstring', it replicates the code using -2 as the
 ** last argument to 'prepbuffsize', signaling that the box is (or will
-** be) bellow the string being added to the buffer. (Box creation can
+** be) below the string being added to the buffer. (Box creation can
 ** trigger an emergency GC, so we should not remove the string from the
 ** stack before we have the space guaranteed.)
 */
@@ -739,17 +740,18 @@ static int errfile (lua_State *L, const char *what, int fnameindex) {
 }
 
 
-static int skipBOM (LoadF *lf) {
-  const char *p = "\xEF\xBB\xBF";  /* UTF-8 BOM mark */
-  int c;
-  lf->n = 0;
-  do {
-    c = getc(lf->f);
-    if (c == EOF || c != *(const unsigned char *)p++) return c;
-    lf->buff[lf->n++] = c;  /* to be read by the parser */
-  } while (*p != '\0');
-  lf->n = 0;  /* prefix matched; discard it */
-  return getc(lf->f);  /* return next character */
+/*
+** Skip an optional BOM at the start of a stream. If there is an
+** incomplete BOM (the first character is correct but the rest is
+** not), returns the first character anyway to force an error
+** (as no chunk can start with 0xEF).
+*/
+static int skipBOM (FILE *f) {
+  int c = getc(f);  /* read first character */
+  if (c == 0xEF && getc(f) == 0xBB && getc(f) == 0xBF)  /* correct BOM? */
+    return getc(f);  /* ignore BOM and return next char */
+  else  /* no (valid) BOM */
+    return c;  /* return first character */
 }
 
 
@@ -760,13 +762,13 @@ static int skipBOM (LoadF *lf) {
 ** first "valid" character of the file (after the optional BOM and
 ** a first-line comment).
 */
-static int skipcomment (LoadF *lf, int *cp) {
-  int c = *cp = skipBOM(lf);
+static int skipcomment (FILE *f, int *cp) {
+  int c = *cp = skipBOM(f);
   if (c == '#') {  /* first line is a comment (Unix exec. file)? */
     do {  /* skip first line */
-      c = getc(lf->f);
+      c = getc(f);
     } while (c != EOF && c != '\n');
-    *cp = getc(lf->f);  /* skip end-of-line, if present */
+    *cp = getc(f);  /* next character after comment, if present */
     return 1;  /* there was a comment */
   }
   else return 0;  /* no comment */
@@ -788,12 +790,16 @@ LUALIB_API int luaL_loadfilex (lua_State *L, const char *filename,
     lf.f = fopen(filename, "r");
     if (lf.f == NULL) return errfile(L, "open", fnameindex);
   }
-  if (skipcomment(&lf, &c))  /* read initial portion */
-    lf.buff[lf.n++] = '\n';  /* add line to correct line numbers */
-  if (c == LUA_SIGNATURE[0] && filename) {  /* binary file? */
-    lf.f = freopen(filename, "rb", lf.f);  /* reopen in binary mode */
-    if (lf.f == NULL) return errfile(L, "reopen", fnameindex);
-    skipcomment(&lf, &c);  /* re-read initial portion */
+  lf.n = 0;
+  if (skipcomment(lf.f, &c))  /* read initial portion */
+    lf.buff[lf.n++] = '\n';  /* add newline to correct line numbers */
+  if (c == LUA_SIGNATURE[0]) {  /* binary file? */
+    lf.n = 0;  /* remove possible newline */
+    if (filename) {  /* "real" file? */
+      lf.f = freopen(filename, "rb", lf.f);  /* reopen in binary mode */
+      if (lf.f == NULL) return errfile(L, "reopen", fnameindex);
+      skipcomment(lf.f, &c);  /* re-read initial portion */
+    }
   }
   if (c != EOF)
     lf.buff[lf.n++] = c;  /* 'c' is the first character of the stream */
diff --git a/src/lcode.c b/src/lcode.c
index 06425a1db800..1a371ca943ba 100644
--- a/src/lcode.c
+++ b/src/lcode.c
@@ -1352,6 +1352,35 @@ static int constfolding (FuncState *fs, int op, expdesc *e1,
 
 
 /*
+** Convert a BinOpr to an OpCode  (ORDER OPR - ORDER OP)
+*/
+l_sinline OpCode binopr2op (BinOpr opr, BinOpr baser, OpCode base) {
+  lua_assert(baser <= opr &&
+            ((baser == OPR_ADD && opr <= OPR_SHR) ||
+             (baser == OPR_LT && opr <= OPR_LE)));
+  return cast(OpCode, (cast_int(opr) - cast_int(baser)) + cast_int(base));
+}
+
+
+/*
+** Convert a UnOpr to an OpCode  (ORDER OPR - ORDER OP)
+*/
+l_sinline OpCode unopr2op (UnOpr opr) {
+  return cast(OpCode, (cast_int(opr) - cast_int(OPR_MINUS)) +
+                                       cast_int(OP_UNM));
+}
+
+
+/*
+** Convert a BinOpr to a tag method  (ORDER OPR - ORDER TM)
+*/
+l_sinline TMS binopr2TM (BinOpr opr) {
+  lua_assert(OPR_ADD <= opr && opr <= OPR_SHR);
+  return cast(TMS, (cast_int(opr) - cast_int(OPR_ADD)) + cast_int(TM_ADD));
+}
+
+
+/*
 ** Emit code for unary expressions that "produce values"
 ** (everything but 'not').
 ** Expression to produce final result will be encoded in 'e'.
@@ -1389,12 +1418,15 @@ static void finishbinexpval (FuncState *fs, expdesc *e1, expdesc *e2,
 ** Emit code for binary expressions that "produce values" over
 ** two registers.
 */
-static void codebinexpval (FuncState *fs, OpCode op,
+static void codebinexpval (FuncState *fs, BinOpr opr,
                            expdesc *e1, expdesc *e2, int line) {
-  int v2 = luaK_exp2anyreg(fs, e2);  /* both operands are in registers */
+  OpCode op = binopr2op(opr, OPR_ADD, OP_ADD);
+  int v2 = luaK_exp2anyreg(fs, e2);  /* make sure 'e2' is in a register */
+  /* 'e1' must be already in a register or it is a constant */
+  lua_assert((VNIL <= e1->k && e1->k <= VKSTR) ||
+             e1->k == VNONRELOC || e1->k == VRELOC);
   lua_assert(OP_ADD <= op && op <= OP_SHR);
-  finishbinexpval(fs, e1, e2, op, v2, 0, line, OP_MMBIN,
-                  cast(TMS, (op - OP_ADD) + TM_ADD));
+  finishbinexpval(fs, e1, e2, op, v2, 0, line, OP_MMBIN, binopr2TM(opr));
 }
 
 
@@ -1410,6 +1442,18 @@ static void codebini (FuncState *fs, OpCode op,
 }
 
 
+/*
+** Code binary operators with K operand.
+*/
+static void codebinK (FuncState *fs, BinOpr opr,
+                      expdesc *e1, expdesc *e2, int flip, int line) {
+  TMS event = binopr2TM(opr);
+  int v2 = e2->u.info;  /* K index */
+  OpCode op = binopr2op(opr, OPR_ADD, OP_ADDK);
+  finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK, event);
+}
+
+
 /* Try to code a binary operator negating its second operand.
 ** For the metamethod, 2nd operand must keep its original value.
 */
@@ -1438,23 +1482,26 @@ static void swapexps (expdesc *e1, expdesc *e2) {
 
 
 /*
+** Code binary operators with no constant operand.
+*/
+static void codebinNoK (FuncState *fs, BinOpr opr,
+                        expdesc *e1, expdesc *e2, int flip, int line) {
+  if (flip)
+    swapexps(e1, e2);  /* back to original order */
+  codebinexpval(fs, opr, e1, e2, line);  /* use standard operators */
+}
+
+
+/*
 ** Code arithmetic operators ('+', '-', ...). If second operand is a
 ** constant in the proper range, use variant opcodes with K operands.
 */
 static void codearith (FuncState *fs, BinOpr opr,
                        expdesc *e1, expdesc *e2, int flip, int line) {
-  TMS event = cast(TMS, opr + TM_ADD);
-  if (tonumeral(e2, NULL) && luaK_exp2K(fs, e2)) {  /* K operand? */
-    int v2 = e2->u.info;  /* K index */
-    OpCode op = cast(OpCode, opr + OP_ADDK);
-    finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK, event);
-  }
-  else {  /* 'e2' is neither an immediate nor a K operand */
-    OpCode op = cast(OpCode, opr + OP_ADD);
-    if (flip)
-      swapexps(e1, e2);  /* back to original order */
-    codebinexpval(fs, op, e1, e2, line);  /* use standard operators */
-  }
+  if (tonumeral(e2, NULL) && luaK_exp2K(fs, e2))  /* K operand? */
+    codebinK(fs, opr, e1, e2, flip, line);
+  else  /* 'e2' is neither an immediate nor a K operand */
+    codebinNoK(fs, opr, e1, e2, flip, line);
 }
 
 
@@ -1471,35 +1518,27 @@ static void codecommutative (FuncState *fs, BinOpr op,
     flip = 1;
   }
   if (op == OPR_ADD && isSCint(e2))  /* immediate operand? */
-    codebini(fs, cast(OpCode, OP_ADDI), e1, e2, flip, line, TM_ADD);
+    codebini(fs, OP_ADDI, e1, e2, flip, line, TM_ADD);
   else
     codearith(fs, op, e1, e2, flip, line);
 }
 
 
 /*
-** Code bitwise operations; they are all associative, so the function
+** Code bitwise operations; they are all commutative, so the function
 ** tries to put an integer constant as the 2nd operand (a K operand).
 */
 static void codebitwise (FuncState *fs, BinOpr opr,
                          expdesc *e1, expdesc *e2, int line) {
   int flip = 0;
-  int v2;
-  OpCode op;
-  if (e1->k == VKINT && luaK_exp2RK(fs, e1)) {
+  if (e1->k == VKINT) {
     swapexps(e1, e2);  /* 'e2' will be the constant operand */
     flip = 1;
   }
-  else if (!(e2->k == VKINT && luaK_exp2RK(fs, e2))) {  /* no constants? */
-    op = cast(OpCode, opr + OP_ADD);
-    codebinexpval(fs, op, e1, e2, line);  /* all-register opcodes */
-    return;
-  }
-  v2 = e2->u.info;  /* index in K array */
-  op = cast(OpCode, opr + OP_ADDK);
-  lua_assert(ttisinteger(&fs->f->k[v2]));
-  finishbinexpval(fs, e1, e2, op, v2, flip, line, OP_MMBINK,
-                  cast(TMS, opr + TM_ADD));
+  if (e2->k == VKINT && luaK_exp2K(fs, e2))  /* K operand? */
+    codebinK(fs, opr, e1, e2, flip, line);
+  else  /* no constants */
+    codebinNoK(fs, opr, e1, e2, flip, line);
 }
 
 
@@ -1507,25 +1546,27 @@ static void codebitwise (FuncState *fs, BinOpr opr,
 ** Emit code for order comparisons. When using an immediate operand,
 ** 'isfloat' tells whether the original value was a float.
 */
-static void codeorder (FuncState *fs, OpCode op, expdesc *e1, expdesc *e2) {
+static void codeorder (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
   int r1, r2;
   int im;
   int isfloat = 0;
+  OpCode op;
   if (isSCnumber(e2, &im, &isfloat)) {
     /* use immediate operand */
     r1 = luaK_exp2anyreg(fs, e1);
     r2 = im;
-    op = cast(OpCode, (op - OP_LT) + OP_LTI);
+    op = binopr2op(opr, OPR_LT, OP_LTI);
   }
   else if (isSCnumber(e1, &im, &isfloat)) {
     /* transform (A < B) to (B > A) and (A <= B) to (B >= A) */
     r1 = luaK_exp2anyreg(fs, e2);
     r2 = im;
-    op = (op == OP_LT) ? OP_GTI : OP_GEI;
+    op = binopr2op(opr, OPR_LT, OP_GTI);
   }
   else {  /* regular case, compare two registers */
     r1 = luaK_exp2anyreg(fs, e1);
     r2 = luaK_exp2anyreg(fs, e2);
+    op = binopr2op(opr, OPR_LT, OP_LT);
   }
   freeexps(fs, e1, e2);
   e1->u.info = condjump(fs, op, r1, r2, isfloat, 1);
@@ -1551,7 +1592,7 @@ static void codeeq (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
     op = OP_EQI;
     r2 = im;  /* immediate operand */
   }
-  else if (luaK_exp2RK(fs, e2)) {  /* 1st expression is constant? */
+  else if (luaK_exp2RK(fs, e2)) {  /* 2nd expression is constant? */
     op = OP_EQK;
     r2 = e2->u.info;  /* constant index */
   }
@@ -1568,16 +1609,16 @@ static void codeeq (FuncState *fs, BinOpr opr, expdesc *e1, expdesc *e2) {
 /*
 ** Apply prefix operation 'op' to expression 'e'.
 */
-void luaK_prefix (FuncState *fs, UnOpr op, expdesc *e, int line) {
+void luaK_prefix (FuncState *fs, UnOpr opr, expdesc *e, int line) {
   static const expdesc ef = {VKINT, {0}, NO_JUMP, NO_JUMP};
   luaK_dischargevars(fs, e);
-  switch (op) {
+  switch (opr) {
     case OPR_MINUS: case OPR_BNOT:  /* use 'ef' as fake 2nd operand */
-      if (constfolding(fs, op + LUA_OPUNM, e, &ef))
+      if (constfolding(fs, opr + LUA_OPUNM, e, &ef))
         break;
       /* else */ /* FALLTHROUGH */
     case OPR_LEN:
-      codeunexpval(fs, cast(OpCode, op + OP_UNM), e, line);
+      codeunexpval(fs, unopr2op(opr), e, line);
       break;
     case OPR_NOT: codenot(fs, e); break;
     default: lua_assert(0);
@@ -1611,7 +1652,8 @@ void luaK_infix (FuncState *fs, BinOpr op, expdesc *v) {
     case OPR_SHL: case OPR_SHR: {
       if (!tonumeral(v, NULL))
         luaK_exp2anyreg(fs, v);
-      /* else keep numeral, which may be folded with 2nd operand */
+      /* else keep numeral, which may be folded or used as an immediate
+         operand */
       break;
     }
     case OPR_EQ: case OPR_NE: {
@@ -1706,30 +1748,27 @@ void luaK_posfix (FuncState *fs, BinOpr opr,
         /* coded as (r1 >> -I) */;
       }
       else  /* regular case (two registers) */
-       codebinexpval(fs, OP_SHL, e1, e2, line);
+       codebinexpval(fs, opr, e1, e2, line);
       break;
     }
     case OPR_SHR: {
       if (isSCint(e2))
         codebini(fs, OP_SHRI, e1, e2, 0, line, TM_SHR);  /* r1 >> I */
       else  /* regular case (two registers) */
-        codebinexpval(fs, OP_SHR, e1, e2, line);
+        codebinexpval(fs, opr, e1, e2, line);
       break;
     }
     case OPR_EQ: case OPR_NE: {
       codeeq(fs, opr, e1, e2);
       break;
     }
-    case OPR_LT: case OPR_LE: {
-      OpCode op = cast(OpCode, (opr - OPR_EQ) + OP_EQ);
-      codeorder(fs, op, e1, e2);
-      break;
-    }
     case OPR_GT: case OPR_GE: {
       /* '(a > b)' <=> '(b < a)';  '(a >= b)' <=> '(b <= a)' */
-      OpCode op = cast(OpCode, (opr - OPR_NE) + OP_EQ);
       swapexps(e1, e2);
-      codeorder(fs, op, e1, e2);
+      opr = cast(BinOpr, (opr - OPR_GT) + OPR_LT);
+    }  /* FALLTHROUGH */
+    case OPR_LT: case OPR_LE: {
+      codeorder(fs, opr, e1, e2);
       break;
     }
     default: lua_assert(0);
diff --git a/src/lcorolib.c b/src/lcorolib.c
index 785a1e81aa0a..c64adf08a8e1 100644
--- a/src/lcorolib.c
+++ b/src/lcorolib.c
@@ -76,7 +76,7 @@ static int luaB_auxwrap (lua_State *L) {
   if (l_unlikely(r < 0)) {  /* error? */
     int stat = lua_status(co);
     if (stat != LUA_OK && stat != LUA_YIELD) {  /* error in the coroutine? */
-      stat = lua_resetthread(co);  /* close its tbc variables */
+      stat = lua_closethread(co, L);  /* close its tbc variables */
       lua_assert(stat != LUA_OK);
       lua_xmove(co, L, 1);  /* move error message to the caller */
     }
@@ -172,7 +172,7 @@ static int luaB_close (lua_State *L) {
   int status = auxstatus(L, co);
   switch (status) {
     case COS_DEAD: case COS_YIELD: {
-      status = lua_resetthread(co);
+      status = lua_closethread(co, L);
       if (status == LUA_OK) {
         lua_pushboolean(L, 1);
         return 1;
diff --git a/src/ldebug.c b/src/ldebug.c
index a716d95e22f6..28b1caabf77e 100644
--- a/src/ldebug.c
+++ b/src/ldebug.c
@@ -182,10 +182,10 @@ static const char *upvalname (const Proto *p, int uv) {
 
 
 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
-  if (clLvalue(s2v(ci->func))->p->is_vararg) {
+  if (clLvalue(s2v(ci->func.p))->p->is_vararg) {
     int nextra = ci->u.l.nextraargs;
     if (n >= -nextra) {  /* 'n' is negative */
-      *pos = ci->func - nextra - (n + 1);
+      *pos = ci->func.p - nextra - (n + 1);
       return "(vararg)";  /* generic name for any vararg */
     }
   }
@@ -194,7 +194,7 @@ static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
 
 
 const char *luaG_findlocal (lua_State *L, CallInfo *ci, int n, StkId *pos) {
-  StkId base = ci->func + 1;
+  StkId base = ci->func.p + 1;
   const char *name = NULL;
   if (isLua(ci)) {
     if (n < 0)  /* access to vararg values? */
@@ -203,7 +203,7 @@ const char *luaG_findlocal (lua_State *L, CallInfo *ci, int n, StkId *pos) {
       name = luaF_getlocalname(ci_func(ci)->p, n, currentpc(ci));
   }
   if (name == NULL) {  /* no 'standard' name? */
-    StkId limit = (ci == L->ci) ? L->top : ci->next->func;
+    StkId limit = (ci == L->ci) ? L->top.p : ci->next->func.p;
     if (limit - base >= n && n > 0) {  /* is 'n' inside 'ci' stack? */
       /* generic name for any valid slot */
       name = isLua(ci) ? "(temporary)" : "(C temporary)";
@@ -221,16 +221,16 @@ LUA_API const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n) {
   const char *name;
   lua_lock(L);
   if (ar == NULL) {  /* information about non-active function? */
-    if (!isLfunction(s2v(L->top - 1)))  /* not a Lua function? */
+    if (!isLfunction(s2v(L->top.p - 1)))  /* not a Lua function? */
       name = NULL;
     else  /* consider live variables at function start (parameters) */
-      name = luaF_getlocalname(clLvalue(s2v(L->top - 1))->p, n, 0);
+      name = luaF_getlocalname(clLvalue(s2v(L->top.p - 1))->p, n, 0);
   }
   else {  /* active function; get information through 'ar' */
     StkId pos = NULL;  /* to avoid warnings */
     name = luaG_findlocal(L, ar->i_ci, n, &pos);
     if (name) {
-      setobjs2s(L, L->top, pos);
+      setobjs2s(L, L->top.p, pos);
       api_incr_top(L);
     }
   }
@@ -245,8 +245,8 @@ LUA_API const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n) {
   lua_lock(L);
   name = luaG_findlocal(L, ar->i_ci, n, &pos);
   if (name) {
-    setobjs2s(L, pos, L->top - 1);
-    L->top--;  /* pop value */
+    setobjs2s(L, pos, L->top.p - 1);
+    L->top.p--;  /* pop value */
   }
   lua_unlock(L);
   return name;
@@ -289,7 +289,7 @@ static int nextline (const Proto *p, int currentline, int pc) {
 
 static void collectvalidlines (lua_State *L, Closure *f) {
   if (noLuaClosure(f)) {
-    setnilvalue(s2v(L->top));
+    setnilvalue(s2v(L->top.p));
     api_incr_top(L);
   }
   else {
@@ -298,7 +298,7 @@ static void collectvalidlines (lua_State *L, Closure *f) {
     const Proto *p = f->l.p;
     int currentline = p->linedefined;
     Table *t = luaH_new(L);  /* new table to store active lines */
-    sethvalue2s(L, L->top, t);  /* push it on stack */
+    sethvalue2s(L, L->top.p, t);  /* push it on stack */
     api_incr_top(L);
     setbtvalue(&v);  /* boolean 'true' to be the value of all indices */
     if (!p->is_vararg)  /* regular function? */
@@ -388,20 +388,20 @@ LUA_API int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar) {
   lua_lock(L);
   if (*what == '>') {
     ci = NULL;
-    func = s2v(L->top - 1);
+    func = s2v(L->top.p - 1);
     api_check(L, ttisfunction(func), "function expected");
     what++;  /* skip the '>' */
-    L->top--;  /* pop function */
+    L->top.p--;  /* pop function */
   }
   else {
     ci = ar->i_ci;
-    func = s2v(ci->func);
+    func = s2v(ci->func.p);
     lua_assert(ttisfunction(func));
   }
   cl = ttisclosure(func) ? clvalue(func) : NULL;
   status = auxgetinfo(L, what, ar, cl, ci);
   if (strchr(what, 'f')) {
-    setobj2s(L, L->top, func);
+    setobj2s(L, L->top.p, func);
     api_incr_top(L);
   }
   if (strchr(what, 'L'))
@@ -656,18 +656,19 @@ static const char *funcnamefromcall (lua_State *L, CallInfo *ci,
 
 
 /*
-** Check whether pointer 'o' points to some value in the stack
-** frame of the current function. Because 'o' may not point to a
-** value in this stack, we cannot compare it with the region
-** boundaries (undefined behaviour in ISO C).
+** Check whether pointer 'o' points to some value in the stack frame of
+** the current function and, if so, returns its index.  Because 'o' may
+** not point to a value in this stack, we cannot compare it with the
+** region boundaries (undefined behavior in ISO C).
 */
-static int isinstack (CallInfo *ci, const TValue *o) {
-  StkId pos;
-  for (pos = ci->func + 1; pos < ci->top; pos++) {
-    if (o == s2v(pos))
-      return 1;
+static int instack (CallInfo *ci, const TValue *o) {
+  int pos;
+  StkId base = ci->func.p + 1;
+  for (pos = 0; base + pos < ci->top.p; pos++) {
+    if (o == s2v(base + pos))
+      return pos;
   }
-  return 0;  /* not found */
+  return -1;  /* not found */
 }
 
 
@@ -681,7 +682,7 @@ static const char *getupvalname (CallInfo *ci, const TValue *o,
   LClosure *c = ci_func(ci);
   int i;
   for (i = 0; i < c->nupvalues; i++) {
-    if (c->upvals[i]->v == o) {
+    if (c->upvals[i]->v.p == o) {
       *name = upvalname(c->p, i);
       return "upvalue";
     }
@@ -708,9 +709,11 @@ static const char *varinfo (lua_State *L, const TValue *o) {
   const char *kind = NULL;
   if (isLua(ci)) {
     kind = getupvalname(ci, o, &name);  /* check whether 'o' is an upvalue */
-    if (!kind && isinstack(ci, o))  /* no? try a register */
-      kind = getobjname(ci_func(ci)->p, currentpc(ci),
-                        cast_int(cast(StkId, o) - (ci->func + 1)), &name);
+    if (!kind) {  /* not an upvalue? */
+      int reg = instack(ci, o);  /* try a register */
+      if (reg >= 0)  /* is 'o' a register? */
+        kind = getobjname(ci_func(ci)->p, currentpc(ci), reg, &name);
+    }
   }
   return formatvarinfo(L, kind, name);
 }
@@ -807,10 +810,10 @@ l_noret luaG_errormsg (lua_State *L) {
   if (L->errfunc != 0) {  /* is there an error handling function? */
     StkId errfunc = restorestack(L, L->errfunc);
     lua_assert(ttisfunction(s2v(errfunc)));
-    setobjs2s(L, L->top, L->top - 1);  /* move argument */
-    setobjs2s(L, L->top - 1, errfunc);  /* push function */
-    L->top++;  /* assume EXTRA_STACK */
-    luaD_callnoyield(L, L->top - 2, 1);  /* call it */
+    setobjs2s(L, L->top.p, L->top.p - 1);  /* move argument */
+    setobjs2s(L, L->top.p - 1, errfunc);  /* push function */
+    L->top.p++;  /* assume EXTRA_STACK */
+    luaD_callnoyield(L, L->top.p - 2, 1);  /* call it */
   }
   luaD_throw(L, LUA_ERRRUN);
 }
@@ -824,8 +827,11 @@ l_noret luaG_runerror (lua_State *L, const char *fmt, ...) {
   va_start(argp, fmt);
   msg = luaO_pushvfstring(L, fmt, argp);  /* format message */
   va_end(argp);
-  if (isLua(ci))  /* if Lua function, add source:line information */
+  if (isLua(ci)) {  /* if Lua function, add source:line information */
     luaG_addinfo(L, msg, ci_func(ci)->p->source, getcurrentline(ci));
+    setobjs2s(L, L->top.p - 2, L->top.p - 1);  /* remove 'msg' */
+    L->top.p--;
+  }
   luaG_errormsg(L);
 }
 
@@ -842,7 +848,7 @@ static int changedline (const Proto *p, int oldpc, int newpc) {
   if (p->lineinfo == NULL)  /* no debug information? */
     return 0;
   if (newpc - oldpc < MAXIWTHABS / 2) {  /* not too far apart? */
-    int delta = 0;  /* line diference */
+    int delta = 0;  /* line difference */
     int pc = oldpc;
     for (;;) {
       int lineinfo = p->lineinfo[++pc];
@@ -869,7 +875,7 @@ static int changedline (const Proto *p, int oldpc, int newpc) {
 ** invalid; if so, use zero as a valid value. (A wrong but valid 'oldpc'
 ** at most causes an extra call to a line hook.)
 ** This function is not "Protected" when called, so it should correct
-** 'L->top' before calling anything that can run the GC.
+** 'L->top.p' before calling anything that can run the GC.
 */
 int luaG_traceexec (lua_State *L, const Instruction *pc) {
   CallInfo *ci = L->ci;
@@ -892,7 +898,7 @@ int luaG_traceexec (lua_State *L, const Instruction *pc) {
     return 1;  /* do not call hook again (VM yielded, so it did not move) */
   }
   if (!isIT(*(ci->u.l.savedpc - 1)))  /* top not being used? */
-    L->top = ci->top;  /* correct top */
+    L->top.p = ci->top.p;  /* correct top */
   if (counthook)
     luaD_hook(L, LUA_HOOKCOUNT, -1, 0, 0);  /* call count hook */
   if (mask & LUA_MASKLINE) {
diff --git a/src/ldebug.h b/src/ldebug.h
index 974960e99da0..2c3074c61b6f 100644
--- a/src/ldebug.h
+++ b/src/ldebug.h
@@ -15,7 +15,7 @@
 
 
 /* Active Lua function (given call info) */
-#define ci_func(ci)		(clLvalue(s2v((ci)->func)))
+#define ci_func(ci)		(clLvalue(s2v((ci)->func.p)))
 
 
 #define resethookcount(L)	(L->hookcount = L->basehookcount)
diff --git a/src/ldo.c b/src/ldo.c
index a48e35f9dba9..2a0017ca62a3 100644
--- a/src/ldo.c
+++ b/src/ldo.c
@@ -104,11 +104,11 @@ void luaD_seterrorobj (lua_State *L, int errcode, StkId oldtop) {
     }
     default: {
       lua_assert(errorstatus(errcode));  /* real error */
-      setobjs2s(L, oldtop, L->top - 1);  /* error message on current top */
+      setobjs2s(L, oldtop, L->top.p - 1);  /* error message on current top */
       break;
     }
   }
-  L->top = oldtop + 1;
+  L->top.p = oldtop + 1;
 }
 
 
@@ -121,7 +121,7 @@ l_noret luaD_throw (lua_State *L, int errcode) {
     global_State *g = G(L);
     errcode = luaE_resetthread(L, errcode);  /* close all upvalues */
     if (g->mainthread->errorJmp) {  /* main thread has a handler? */
-      setobjs2s(L, g->mainthread->top++, L->top - 1);  /* copy error obj. */
+      setobjs2s(L, g->mainthread->top.p++, L->top.p - 1);  /* copy error obj. */
       luaD_throw(g->mainthread, errcode);  /* re-throw in main thread */
     }
     else {  /* no handler at all; abort */
@@ -157,16 +157,38 @@ int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 ** Stack reallocation
 ** ===================================================================
 */
-static void correctstack (lua_State *L, StkId oldstack, StkId newstack) {
+
+
+/*
+** Change all pointers to the stack into offsets.
+*/
+static void relstack (lua_State *L) {
+  CallInfo *ci;
+  UpVal *up;
+  L->top.offset = savestack(L, L->top.p);
+  L->tbclist.offset = savestack(L, L->tbclist.p);
+  for (up = L->openupval; up != NULL; up = up->u.open.next)
+    up->v.offset = savestack(L, uplevel(up));
+  for (ci = L->ci; ci != NULL; ci = ci->previous) {
+    ci->top.offset = savestack(L, ci->top.p);
+    ci->func.offset = savestack(L, ci->func.p);
+  }
+}
+
+
+/*
+** Change back all offsets into pointers.
+*/
+static void correctstack (lua_State *L) {
   CallInfo *ci;
   UpVal *up;
-  L->top = (L->top - oldstack) + newstack;
-  L->tbclist = (L->tbclist - oldstack) + newstack;
+  L->top.p = restorestack(L, L->top.offset);
+  L->tbclist.p = restorestack(L, L->tbclist.offset);
   for (up = L->openupval; up != NULL; up = up->u.open.next)
-    up->v = s2v((uplevel(up) - oldstack) + newstack);
+    up->v.p = s2v(restorestack(L, up->v.offset));
   for (ci = L->ci; ci != NULL; ci = ci->previous) {
-    ci->top = (ci->top - oldstack) + newstack;
-    ci->func = (ci->func - oldstack) + newstack;
+    ci->top.p = restorestack(L, ci->top.offset);
+    ci->func.p = restorestack(L, ci->func.offset);
     if (isLua(ci))
       ci->u.l.trap = 1;  /* signal to update 'trap' in 'luaV_execute' */
   }
@@ -176,44 +198,45 @@ static void correctstack (lua_State *L, StkId oldstack, StkId newstack) {
 /* some space for error handling */
 #define ERRORSTACKSIZE	(LUAI_MAXSTACK + 200)
 
-
 /*
-** Reallocate the stack to a new size, correcting all pointers into
-** it. (There are pointers to a stack from its upvalues, from its list
-** of call infos, plus a few individual pointers.) The reallocation is
-** done in two steps (allocation + free) because the correction must be
-** done while both addresses (the old stack and the new one) are valid.
-** (In ISO C, any pointer use after the pointer has been deallocated is
-** undefined behavior.)
+** Reallocate the stack to a new size, correcting all pointers into it.
+** In ISO C, any pointer use after the pointer has been deallocated is
+** undefined behavior. So, before the reallocation, all pointers are
+** changed to offsets, and after the reallocation they are changed back
+** to pointers. As during the reallocation the pointers are invalid, the
+** reallocation cannot run emergency collections.
+**
 ** In case of allocation error, raise an error or return false according
 ** to 'raiseerror'.
 */
 int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
   int oldsize = stacksize(L);
   int i;
-  StkId newstack = luaM_reallocvector(L, NULL, 0,
-                                      newsize + EXTRA_STACK, StackValue);
+  StkId newstack;
+  int oldgcstop = G(L)->gcstopem;
   lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
+  relstack(L);  /* change pointers to offsets */
+  G(L)->gcstopem = 1;  /* stop emergency collection */
+  newstack = luaM_reallocvector(L, L->stack.p, oldsize + EXTRA_STACK,
+                                   newsize + EXTRA_STACK, StackValue);
+  G(L)->gcstopem = oldgcstop;  /* restore emergency collection */
   if (l_unlikely(newstack == NULL)) {  /* reallocation failed? */
+    correctstack(L);  /* change offsets back to pointers */
     if (raiseerror)
       luaM_error(L);
     else return 0;  /* do not raise an error */
   }
-  /* number of elements to be copied to the new stack */
-  i = ((oldsize <= newsize) ? oldsize : newsize) + EXTRA_STACK;
-  memcpy(newstack, L->stack, i * sizeof(StackValue));
-  for (; i < newsize + EXTRA_STACK; i++)
+  L->stack.p = newstack;
+  correctstack(L);  /* change offsets back to pointers */
+  L->stack_last.p = L->stack.p + newsize;
+  for (i = oldsize + EXTRA_STACK; i < newsize + EXTRA_STACK; i++)
     setnilvalue(s2v(newstack + i)); /* erase new segment */
-  correctstack(L, L->stack, newstack);
-  luaM_freearray(L, L->stack, oldsize + EXTRA_STACK);
-  L->stack = newstack;
-  L->stack_last = L->stack + newsize;
   return 1;
 }
 
 
 /*
-** Try to grow the stack by at least 'n' elements. when 'raiseerror'
+** Try to grow the stack by at least 'n' elements. When 'raiseerror'
 ** is true, raises any error; otherwise, return 0 in case of errors.
 */
 int luaD_growstack (lua_State *L, int n, int raiseerror) {
@@ -227,35 +250,38 @@ int luaD_growstack (lua_State *L, int n, int raiseerror) {
       luaD_throw(L, LUA_ERRERR);  /* error inside message handler */
     return 0;  /* if not 'raiseerror', just signal it */
   }
-  else {
+  else if (n < LUAI_MAXSTACK) {  /* avoids arithmetic overflows */
     int newsize = 2 * size;  /* tentative new size */
-    int needed = cast_int(L->top - L->stack) + n;
+    int needed = cast_int(L->top.p - L->stack.p) + n;
     if (newsize > LUAI_MAXSTACK)  /* cannot cross the limit */
       newsize = LUAI_MAXSTACK;
     if (newsize < needed)  /* but must respect what was asked for */
       newsize = needed;
     if (l_likely(newsize <= LUAI_MAXSTACK))
       return luaD_reallocstack(L, newsize, raiseerror);
-    else {  /* stack overflow */
-      /* add extra size to be able to handle the error message */
-      luaD_reallocstack(L, ERRORSTACKSIZE, raiseerror);
-      if (raiseerror)
-        luaG_runerror(L, "stack overflow");
-      return 0;
-    }
   }
+  /* else stack overflow */
+  /* add extra size to be able to handle the error message */
+  luaD_reallocstack(L, ERRORSTACKSIZE, raiseerror);
+  if (raiseerror)
+    luaG_runerror(L, "stack overflow");
+  return 0;
 }
 
 
+/*
+** Compute how much of the stack is being used, by computing the
+** maximum top of all call frames in the stack and the current top.
+*/
 static int stackinuse (lua_State *L) {
   CallInfo *ci;
   int res;
-  StkId lim = L->top;
+  StkId lim = L->top.p;
   for (ci = L->ci; ci != NULL; ci = ci->previous) {
-    if (lim < ci->top) lim = ci->top;
+    if (lim < ci->top.p) lim = ci->top.p;
   }
-  lua_assert(lim <= L->stack_last);
-  res = cast_int(lim - L->stack) + 1;  /* part of stack in use */
+  lua_assert(lim <= L->stack_last.p + EXTRA_STACK);
+  res = cast_int(lim - L->stack.p) + 1;  /* part of stack in use */
   if (res < LUA_MINSTACK)
     res = LUA_MINSTACK;  /* ensure a minimum size */
   return res;
@@ -273,17 +299,13 @@ static int stackinuse (lua_State *L) {
 */
 void luaD_shrinkstack (lua_State *L) {
   int inuse = stackinuse(L);
-  int nsize = inuse * 2;  /* proposed new size */
-  int max = inuse * 3;  /* maximum "reasonable" size */
-  if (max > LUAI_MAXSTACK) {
-    max = LUAI_MAXSTACK;  /* respect stack limit */
-    if (nsize > LUAI_MAXSTACK)
-      nsize = LUAI_MAXSTACK;
-  }
+  int max = (inuse > LUAI_MAXSTACK / 3) ? LUAI_MAXSTACK : inuse * 3;
   /* if thread is currently not handling a stack overflow and its
      size is larger than maximum "reasonable" size, shrink it */
-  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max)
+  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max) {
+    int nsize = (inuse > LUAI_MAXSTACK / 2) ? LUAI_MAXSTACK : inuse * 2;
     luaD_reallocstack(L, nsize, 0);  /* ok if that fails */
+  }
   else  /* don't change stack */
     condmovestack(L,{},{});  /* (change only for debugging) */
   luaE_shrinkCI(L);  /* shrink CI list */
@@ -292,7 +314,7 @@ void luaD_shrinkstack (lua_State *L) {
 
 void luaD_inctop (lua_State *L) {
   luaD_checkstack(L, 1);
-  L->top++;
+  L->top.p++;
 }
 
 /* }================================================================== */
@@ -309,8 +331,8 @@ void luaD_hook (lua_State *L, int event, int line,
   if (hook && L->allowhook) {  /* make sure there is a hook */
     int mask = CIST_HOOKED;
     CallInfo *ci = L->ci;
-    ptrdiff_t top = savestack(L, L->top);  /* preserve original 'top' */
-    ptrdiff_t ci_top = savestack(L, ci->top);  /* idem for 'ci->top' */
+    ptrdiff_t top = savestack(L, L->top.p);  /* preserve original 'top' */
+    ptrdiff_t ci_top = savestack(L, ci->top.p);  /* idem for 'ci->top' */
     lua_Debug ar;
     ar.event = event;
     ar.currentline = line;
@@ -320,11 +342,11 @@ void luaD_hook (lua_State *L, int event, int line,
       ci->u2.transferinfo.ftransfer = ftransfer;
       ci->u2.transferinfo.ntransfer = ntransfer;
     }
-    if (isLua(ci) && L->top < ci->top)
-      L->top = ci->top;  /* protect entire activation register */
+    if (isLua(ci) && L->top.p < ci->top.p)
+      L->top.p = ci->top.p;  /* protect entire activation register */
     luaD_checkstack(L, LUA_MINSTACK);  /* ensure minimum stack size */
-    if (ci->top < L->top + LUA_MINSTACK)
-      ci->top = L->top + LUA_MINSTACK;
+    if (ci->top.p < L->top.p + LUA_MINSTACK)
+      ci->top.p = L->top.p + LUA_MINSTACK;
     L->allowhook = 0;  /* cannot call hooks inside a hook */
     ci->callstatus |= mask;
     lua_unlock(L);
@@ -332,8 +354,8 @@ void luaD_hook (lua_State *L, int event, int line,
     lua_lock(L);
     lua_assert(!L->allowhook);
     L->allowhook = 1;
-    ci->top = restorestack(L, ci_top);
-    L->top = restorestack(L, top);
+    ci->top.p = restorestack(L, ci_top);
+    L->top.p = restorestack(L, top);
     ci->callstatus &= ~mask;
   }
 }
@@ -364,7 +386,7 @@ void luaD_hookcall (lua_State *L, CallInfo *ci) {
 */
 static void rethook (lua_State *L, CallInfo *ci, int nres) {
   if (L->hookmask & LUA_MASKRET) {  /* is return hook on? */
-    StkId firstres = L->top - nres;  /* index of first result */
+    StkId firstres = L->top.p - nres;  /* index of first result */
     int delta = 0;  /* correction for vararg functions */
     int ftransfer;
     if (isLua(ci)) {
@@ -372,10 +394,10 @@ static void rethook (lua_State *L, CallInfo *ci, int nres) {
       if (p->is_vararg)
         delta = ci->u.l.nextraargs + p->numparams + 1;
     }
-    ci->func += delta;  /* if vararg, back to virtual 'func' */
-    ftransfer = cast(unsigned short, firstres - ci->func);
+    ci->func.p += delta;  /* if vararg, back to virtual 'func' */
+    ftransfer = cast(unsigned short, firstres - ci->func.p);
     luaD_hook(L, LUA_HOOKRET, -1, ftransfer, nres);  /* call it */
-    ci->func -= delta;
+    ci->func.p -= delta;
   }
   if (isLua(ci = ci->previous))
     L->oldpc = pcRel(ci->u.l.savedpc, ci_func(ci)->p);  /* set 'oldpc' */
@@ -394,9 +416,9 @@ StkId luaD_tryfuncTM (lua_State *L, StkId func) {
   tm = luaT_gettmbyobj(L, s2v(func), TM_CALL);  /* (after previous GC) */
   if (l_unlikely(ttisnil(tm)))
     luaG_callerror(L, s2v(func));  /* nothing to call */
-  for (p = L->top; p > func; p--)  /* open space for metamethod */
+  for (p = L->top.p; p > func; p--)  /* open space for metamethod */
     setobjs2s(L, p, p-1);
-  L->top++;  /* stack space pre-allocated by the caller */
+  L->top.p++;  /* stack space pre-allocated by the caller */
   setobj2s(L, func, tm);  /* metamethod is the new function to be called */
   return func;
 }
@@ -413,28 +435,29 @@ l_sinline void moveresults (lua_State *L, StkId res, int nres, int wanted) {
   int i;
   switch (wanted) {  /* handle typical cases separately */
     case 0:  /* no values needed */
-      L->top = res;
+      L->top.p = res;
       return;
     case 1:  /* one value needed */
       if (nres == 0)   /* no results? */
         setnilvalue(s2v(res));  /* adjust with nil */
       else  /* at least one result */
-        setobjs2s(L, res, L->top - nres);  /* move it to proper place */
-      L->top = res + 1;
+        setobjs2s(L, res, L->top.p - nres);  /* move it to proper place */
+      L->top.p = res + 1;
       return;
     case LUA_MULTRET:
       wanted = nres;  /* we want all results */
       break;
     default:  /* two/more results and/or to-be-closed variables */
       if (hastocloseCfunc(wanted)) {  /* to-be-closed variables? */
-        ptrdiff_t savedres = savestack(L, res);
         L->ci->callstatus |= CIST_CLSRET;  /* in case of yields */
         L->ci->u2.nres = nres;
-        luaF_close(L, res, CLOSEKTOP, 1);
+        res = luaF_close(L, res, CLOSEKTOP, 1);
         L->ci->callstatus &= ~CIST_CLSRET;
-        if (L->hookmask)  /* if needed, call hook after '__close's */
+        if (L->hookmask) {  /* if needed, call hook after '__close's */
+          ptrdiff_t savedres = savestack(L, res);
           rethook(L, L->ci, nres);
-        res = restorestack(L, savedres);  /* close and hook can move stack */
+          res = restorestack(L, savedres);  /* hook can move stack */
+        }
         wanted = decodeNresults(wanted);
         if (wanted == LUA_MULTRET)
           wanted = nres;  /* we want all results */
@@ -442,14 +465,14 @@ l_sinline void moveresults (lua_State *L, StkId res, int nres, int wanted) {
       break;
   }
   /* generic case */
-  firstresult = L->top - nres;  /* index of first result */
+  firstresult = L->top.p - nres;  /* index of first result */
   if (nres > wanted)  /* extra results? */
     nres = wanted;  /* don't need them */
   for (i = 0; i < nres; i++)  /* move all results to correct place */
     setobjs2s(L, res + i, firstresult + i);
   for (; i < wanted; i++)  /* complete wanted number of results */
     setnilvalue(s2v(res + i));
-  L->top = res + wanted;  /* top points after the last result */
+  L->top.p = res + wanted;  /* top points after the last result */
 }
 
 
@@ -464,7 +487,7 @@ void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
   if (l_unlikely(L->hookmask && !hastocloseCfunc(wanted)))
     rethook(L, ci, nres);
   /* move results to proper place */
-  moveresults(L, ci->func, nres, wanted);
+  moveresults(L, ci->func.p, nres, wanted);
   /* function cannot be in any of these cases when returning */
   lua_assert(!(ci->callstatus &
         (CIST_HOOKED | CIST_YPCALL | CIST_FIN | CIST_TRAN | CIST_CLSRET)));
@@ -479,10 +502,10 @@ void luaD_poscall (lua_State *L, CallInfo *ci, int nres) {
 l_sinline CallInfo *prepCallInfo (lua_State *L, StkId func, int nret,
                                                 int mask, StkId top) {
   CallInfo *ci = L->ci = next_ci(L);  /* new frame */
-  ci->func = func;
+  ci->func.p = func;
   ci->nresults = nret;
   ci->callstatus = mask;
-  ci->top = top;
+  ci->top.p = top;
   return ci;
 }
 
@@ -496,10 +519,10 @@ l_sinline int precallC (lua_State *L, StkId func, int nresults,
   CallInfo *ci;
   checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
   L->ci = ci = prepCallInfo(L, func, nresults, CIST_C,
-                               L->top + LUA_MINSTACK);
-  lua_assert(ci->top <= L->stack_last);
+                               L->top.p + LUA_MINSTACK);
+  lua_assert(ci->top.p <= L->stack_last.p);
   if (l_unlikely(L->hookmask & LUA_MASKCALL)) {
-    int narg = cast_int(L->top - func) - 1;
+    int narg = cast_int(L->top.p - func) - 1;
     luaD_hook(L, LUA_HOOKCALL, -1, 1, narg);
   }
   lua_unlock(L);
@@ -531,17 +554,17 @@ int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
       int nfixparams = p->numparams;
       int i;
       checkstackGCp(L, fsize - delta, func);
-      ci->func -= delta;  /* restore 'func' (if vararg) */
+      ci->func.p -= delta;  /* restore 'func' (if vararg) */
       for (i = 0; i < narg1; i++)  /* move down function and arguments */
-        setobjs2s(L, ci->func + i, func + i);
-      func = ci->func;  /* moved-down function */
+        setobjs2s(L, ci->func.p + i, func + i);
+      func = ci->func.p;  /* moved-down function */
       for (; narg1 <= nfixparams; narg1++)
         setnilvalue(s2v(func + narg1));  /* complete missing arguments */
-      ci->top = func + 1 + fsize;  /* top for new function */
-      lua_assert(ci->top <= L->stack_last);
+      ci->top.p = func + 1 + fsize;  /* top for new function */
+      lua_assert(ci->top.p <= L->stack_last.p);
       ci->u.l.savedpc = p->code;  /* starting point */
       ci->callstatus |= CIST_TAIL;
-      L->top = func + narg1;  /* set top */
+      L->top.p = func + narg1;  /* set top */
       return -1;
     }
     default: {  /* not a function */
@@ -574,15 +597,15 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
     case LUA_VLCL: {  /* Lua function */
       CallInfo *ci;
       Proto *p = clLvalue(s2v(func))->p;
-      int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
+      int narg = cast_int(L->top.p - func) - 1;  /* number of real arguments */
       int nfixparams = p->numparams;
       int fsize = p->maxstacksize;  /* frame size */
       checkstackGCp(L, fsize, func);
       L->ci = ci = prepCallInfo(L, func, nresults, 0, func + 1 + fsize);
       ci->u.l.savedpc = p->code;  /* starting point */
       for (; narg < nfixparams; narg++)
-        setnilvalue(s2v(L->top++));  /* complete missing arguments */
-      lua_assert(ci->top <= L->stack_last);
+        setnilvalue(s2v(L->top.p++));  /* complete missing arguments */
+      lua_assert(ci->top.p <= L->stack_last.p);
       return ci;
     }
     default: {  /* not a function */
@@ -598,12 +621,17 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
 ** Call a function (C or Lua) through C. 'inc' can be 1 (increment
 ** number of recursive invocations in the C stack) or nyci (the same
 ** plus increment number of non-yieldable calls).
+** This function can be called with some use of EXTRA_STACK, so it should
+** check the stack before doing anything else. 'luaD_precall' already
+** does that.
 */
-l_sinline void ccall (lua_State *L, StkId func, int nResults, int inc) {
+l_sinline void ccall (lua_State *L, StkId func, int nResults, l_uint32 inc) {
   CallInfo *ci;
   L->nCcalls += inc;
-  if (l_unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
+  if (l_unlikely(getCcalls(L) >= LUAI_MAXCCALLS)) {
+    checkstackp(L, 0, func);  /* free any use of EXTRA_STACK */
     luaE_checkcstack(L);
+  }
   if ((ci = luaD_precall(L, func, nResults)) != NULL) {  /* Lua function? */
     ci->callstatus = CIST_FRESH;  /* mark that it is a "fresh" execute */
     luaV_execute(L, ci);  /* call it */
@@ -651,8 +679,7 @@ static int finishpcallk (lua_State *L,  CallInfo *ci) {
   else {  /* error */
     StkId func = restorestack(L, ci->u2.funcidx);
     L->allowhook = getoah(ci->callstatus);  /* restore 'allowhook' */
-    luaF_close(L, func, status, 1);  /* can yield or raise an error */
-    func = restorestack(L, ci->u2.funcidx);  /* stack may be moved */
+    func = luaF_close(L, func, status, 1);  /* can yield or raise an error */
     luaD_seterrorobj(L, status, func);
     luaD_shrinkstack(L);   /* restore stack size in case of overflow */
     setcistrecst(ci, LUA_OK);  /* clear original status */
@@ -740,8 +767,8 @@ static CallInfo *findpcall (lua_State *L) {
 ** coroutine error handler and should not kill the coroutine.)
 */
 static int resume_error (lua_State *L, const char *msg, int narg) {
-  L->top -= narg;  /* remove args from the stack */
-  setsvalue2s(L, L->top, luaS_new(L, msg));  /* push error message */
+  L->top.p -= narg;  /* remove args from the stack */
+  setsvalue2s(L, L->top.p, luaS_new(L, msg));  /* push error message */
   api_incr_top(L);
   lua_unlock(L);
   return LUA_ERRRUN;
@@ -757,7 +784,7 @@ static int resume_error (lua_State *L, const char *msg, int narg) {
 */
 static void resume (lua_State *L, void *ud) {
   int n = *(cast(int*, ud));  /* number of arguments */
-  StkId firstArg = L->top - n;  /* first argument */
+  StkId firstArg = L->top.p - n;  /* first argument */
   CallInfo *ci = L->ci;
   if (L->status == LUA_OK)  /* starting a coroutine? */
     ccall(L, firstArg - 1, LUA_MULTRET, 0);  /* just call its body */
@@ -765,7 +792,7 @@ static void resume (lua_State *L, void *ud) {
     lua_assert(L->status == LUA_YIELD);
     L->status = LUA_OK;  /* mark that it is running (again) */
     if (isLua(ci)) {  /* yielded inside a hook? */
-      L->top = firstArg;  /* discard arguments */
+      L->top.p = firstArg;  /* discard arguments */
       luaV_execute(L, ci);  /* just continue running Lua code */
     }
     else {  /* 'common' yield */
@@ -808,7 +835,7 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
   if (L->status == LUA_OK) {  /* may be starting a coroutine */
     if (L->ci != &L->base_ci)  /* not in base level? */
       return resume_error(L, "cannot resume non-suspended coroutine", nargs);
-    else if (L->top - (L->ci->func + 1) == nargs)  /* no function? */
+    else if (L->top.p - (L->ci->func.p + 1) == nargs)  /* no function? */
       return resume_error(L, "cannot resume dead coroutine", nargs);
   }
   else if (L->status != LUA_YIELD)  /* ended with errors? */
@@ -826,11 +853,11 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs,
     lua_assert(status == L->status);  /* normal end or yield */
   else {  /* unrecoverable error */
     L->status = cast_byte(status);  /* mark thread as 'dead' */
-    luaD_seterrorobj(L, status, L->top);  /* push error message */
-    L->ci->top = L->top;
+    luaD_seterrorobj(L, status, L->top.p);  /* push error message */
+    L->ci->top.p = L->top.p;
   }
   *nresults = (status == LUA_YIELD) ? L->ci->u2.nyield
-                                    : cast_int(L->top - (L->ci->func + 1));
+                                    : cast_int(L->top.p - (L->ci->func.p + 1));
   lua_unlock(L);
   return status;
 }
@@ -985,7 +1012,7 @@ int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
   p.dyd.gt.arr = NULL; p.dyd.gt.size = 0;
   p.dyd.label.arr = NULL; p.dyd.label.size = 0;
   luaZ_initbuffer(L, &p.buff);
-  status = luaD_pcall(L, f_parser, &p, savestack(L, L->top), L->errfunc);
+  status = luaD_pcall(L, f_parser, &p, savestack(L, L->top.p), L->errfunc);
   luaZ_freebuffer(L, &p.buff);
   luaM_freearray(L, p.dyd.actvar.arr, p.dyd.actvar.size);
   luaM_freearray(L, p.dyd.gt.arr, p.dyd.gt.size);
diff --git a/src/ldo.h b/src/ldo.h
index 911e67f660a1..1aa446ad09e9 100644
--- a/src/ldo.h
+++ b/src/ldo.h
@@ -8,6 +8,7 @@
 #define ldo_h
 
 
+#include "llimits.h"
 #include "lobject.h"
 #include "lstate.h"
 #include "lzio.h"
@@ -23,7 +24,7 @@
 ** at every check.
 */
 #define luaD_checkstackaux(L,n,pre,pos)  \
-	if (l_unlikely(L->stack_last - L->top <= (n))) \
+	if (l_unlikely(L->stack_last.p - L->top.p <= (n))) \
 	  { pre; luaD_growstack(L, n, 1); pos; } \
         else { condmovestack(L,pre,pos); }
 
@@ -32,11 +33,18 @@
 
 
 
-#define savestack(L,p)		((char *)(p) - (char *)L->stack)
-#define restorestack(L,n)	((StkId)((char *)L->stack + (n)))
+#define savestack(L,pt)		(cast_charp(pt) - cast_charp(L->stack.p))
+#define restorestack(L,n)	cast(StkId, cast_charp(L->stack.p) + (n))
 
 
 /* macro to check stack size, preserving 'p' */
+#define checkstackp(L,n,p)  \
+  luaD_checkstackaux(L, n, \
+    ptrdiff_t t__ = savestack(L, p),  /* save 'p' */ \
+    p = restorestack(L, t__))  /* 'pos' part: restore 'p' */
+
+
+/* macro to check stack size and GC, preserving 'p' */
 #define checkstackGCp(L,n,p)  \
   luaD_checkstackaux(L, n, \
     ptrdiff_t t__ = savestack(L, p);  /* save 'p' */ \
@@ -58,7 +66,8 @@ LUAI_FUNC int luaD_protectedparser (lua_State *L, ZIO *z, const char *name,
 LUAI_FUNC void luaD_hook (lua_State *L, int event, int line,
                                         int fTransfer, int nTransfer);
 LUAI_FUNC void luaD_hookcall (lua_State *L, CallInfo *ci);
-LUAI_FUNC int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,                                                    int narg1, int delta);
+LUAI_FUNC int luaD_pretailcall (lua_State *L, CallInfo *ci, StkId func,
+                                              int narg1, int delta);
 LUAI_FUNC CallInfo *luaD_precall (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_call (lua_State *L, StkId func, int nResults);
 LUAI_FUNC void luaD_callnoyield (lua_State *L, StkId func, int nResults);
diff --git a/src/ldump.c b/src/ldump.c
index f848b669cbdd..f231691b7795 100644
--- a/src/ldump.c
+++ b/src/ldump.c
@@ -10,6 +10,7 @@
 #include "lprefix.h"
 
 
+#include <limits.h>
 #include <stddef.h>
 
 #include "lua.h"
@@ -55,8 +56,11 @@ static void dumpByte (DumpState *D, int y) {
 }
 
 
-/* dumpInt Buff Size */
-#define DIBS    ((sizeof(size_t) * 8 / 7) + 1)
+/*
+** 'dumpSize' buffer size: each byte can store up to 7 bits. (The "+6"
+** rounds up the division.)
+*/
+#define DIBS    ((sizeof(size_t) * CHAR_BIT + 6) / 7)
 
 static void dumpSize (DumpState *D, size_t x) {
   lu_byte buff[DIBS];
diff --git a/src/lfunc.c b/src/lfunc.c
index f5889a21d12e..0945f241de2d 100644
--- a/src/lfunc.c
+++ b/src/lfunc.c
@@ -50,8 +50,8 @@ void luaF_initupvals (lua_State *L, LClosure *cl) {
   for (i = 0; i < cl->nupvalues; i++) {
     GCObject *o = luaC_newobj(L, LUA_VUPVAL, sizeof(UpVal));
     UpVal *uv = gco2upv(o);
-    uv->v = &uv->u.value;  /* make it closed */
-    setnilvalue(uv->v);
+    uv->v.p = &uv->u.value;  /* make it closed */
+    setnilvalue(uv->v.p);
     cl->upvals[i] = uv;
     luaC_objbarrier(L, cl, uv);
   }
@@ -62,12 +62,11 @@ void luaF_initupvals (lua_State *L, LClosure *cl) {
 ** Create a new upvalue at the given level, and link it to the list of
 ** open upvalues of 'L' after entry 'prev'.
 **/
-static UpVal *newupval (lua_State *L, int tbc, StkId level, UpVal **prev) {
+static UpVal *newupval (lua_State *L, StkId level, UpVal **prev) {
   GCObject *o = luaC_newobj(L, LUA_VUPVAL, sizeof(UpVal));
   UpVal *uv = gco2upv(o);
   UpVal *next = *prev;
-  uv->v = s2v(level);  /* current value lives in the stack */
-  uv->tbc = tbc;
+  uv->v.p = s2v(level);  /* current value lives in the stack */
   uv->u.open.next = next;  /* link it to list of open upvalues */
   uv->u.open.previous = prev;
   if (next)
@@ -96,7 +95,7 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
     pp = &p->u.open.next;
   }
   /* not found: create a new upvalue after 'pp' */
-  return newupval(L, 0, level, pp);
+  return newupval(L, level, pp);
 }
 
 
@@ -106,12 +105,12 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
 ** (This function assumes EXTRA_STACK.)
 */
 static void callclosemethod (lua_State *L, TValue *obj, TValue *err, int yy) {
-  StkId top = L->top;
+  StkId top = L->top.p;
   const TValue *tm = luaT_gettmbyobj(L, obj, TM_CLOSE);
   setobj2s(L, top, tm);  /* will call metamethod... */
   setobj2s(L, top + 1, obj);  /* with 'self' as the 1st argument */
   setobj2s(L, top + 2, err);  /* and error msg. as 2nd argument */
-  L->top = top + 3;  /* add function and arguments */
+  L->top.p = top + 3;  /* add function and arguments */
   if (yy)
     luaD_call(L, top, 0);
   else
@@ -126,7 +125,7 @@ static void callclosemethod (lua_State *L, TValue *obj, TValue *err, int yy) {
 static void checkclosemth (lua_State *L, StkId level) {
   const TValue *tm = luaT_gettmbyobj(L, s2v(level), TM_CLOSE);
   if (ttisnil(tm)) {  /* no metamethod? */
-    int idx = cast_int(level - L->ci->func);  /* variable index */
+    int idx = cast_int(level - L->ci->func.p);  /* variable index */
     const char *vname = luaG_findlocal(L, L->ci, idx, NULL);
     if (vname == NULL) vname = "?";
     luaG_runerror(L, "variable '%s' got a non-closable value", vname);
@@ -160,23 +159,23 @@ static void prepcallclosemth (lua_State *L, StkId level, int status, int yy) {
 ** is used.)
 */
 #define MAXDELTA  \
-	((256ul << ((sizeof(L->stack->tbclist.delta) - 1) * 8)) - 1)
+	((256ul << ((sizeof(L->stack.p->tbclist.delta) - 1) * 8)) - 1)
 
 
 /*
 ** Insert a variable in the list of to-be-closed variables.
 */
 void luaF_newtbcupval (lua_State *L, StkId level) {
-  lua_assert(level > L->tbclist);
+  lua_assert(level > L->tbclist.p);
   if (l_isfalse(s2v(level)))
     return;  /* false doesn't need to be closed */
   checkclosemth(L, level);  /* value must have a close method */
-  while (cast_uint(level - L->tbclist) > MAXDELTA) {
-    L->tbclist += MAXDELTA;  /* create a dummy node at maximum delta */
-    L->tbclist->tbclist.delta = 0;
+  while (cast_uint(level - L->tbclist.p) > MAXDELTA) {
+    L->tbclist.p += MAXDELTA;  /* create a dummy node at maximum delta */
+    L->tbclist.p->tbclist.delta = 0;
   }
-  level->tbclist.delta = cast(unsigned short, level - L->tbclist);
-  L->tbclist = level;
+  level->tbclist.delta = cast(unsigned short, level - L->tbclist.p);
+  L->tbclist.p = level;
 }
 
 
@@ -196,10 +195,10 @@ void luaF_closeupval (lua_State *L, StkId level) {
   StkId upl;  /* stack index pointed by 'uv' */
   while ((uv = L->openupval) != NULL && (upl = uplevel(uv)) >= level) {
     TValue *slot = &uv->u.value;  /* new position for value */
-    lua_assert(uplevel(uv) < L->top);
+    lua_assert(uplevel(uv) < L->top.p);
     luaF_unlinkupval(uv);  /* remove upvalue from 'openupval' list */
-    setobj(L, slot, uv->v);  /* move value to upvalue slot */
-    uv->v = slot;  /* now current value lives here */
+    setobj(L, slot, uv->v.p);  /* move value to upvalue slot */
+    uv->v.p = slot;  /* now current value lives here */
     if (!iswhite(uv)) {  /* neither white nor dead? */
       nw2black(uv);  /* closed upvalues cannot be gray */
       luaC_barrier(L, uv, slot);
@@ -209,31 +208,32 @@ void luaF_closeupval (lua_State *L, StkId level) {
 
 
 /*
-** Remove firt element from the tbclist plus its dummy nodes.
+** Remove first element from the tbclist plus its dummy nodes.
 */
 static void poptbclist (lua_State *L) {
-  StkId tbc = L->tbclist;
+  StkId tbc = L->tbclist.p;
   lua_assert(tbc->tbclist.delta > 0);  /* first element cannot be dummy */
   tbc -= tbc->tbclist.delta;
-  while (tbc > L->stack && tbc->tbclist.delta == 0)
+  while (tbc > L->stack.p && tbc->tbclist.delta == 0)
     tbc -= MAXDELTA;  /* remove dummy nodes */
-  L->tbclist = tbc;
+  L->tbclist.p = tbc;
 }
 
 
 /*
 ** Close all upvalues and to-be-closed variables up to the given stack
-** level.
+** level. Return restored 'level'.
 */
-void luaF_close (lua_State *L, StkId level, int status, int yy) {
+StkId luaF_close (lua_State *L, StkId level, int status, int yy) {
   ptrdiff_t levelrel = savestack(L, level);
   luaF_closeupval(L, level);  /* first, close the upvalues */
-  while (L->tbclist >= level) {  /* traverse tbc's down to that level */
-    StkId tbc = L->tbclist;  /* get variable index */
+  while (L->tbclist.p >= level) {  /* traverse tbc's down to that level */
+    StkId tbc = L->tbclist.p;  /* get variable index */
     poptbclist(L);  /* remove it from list */
     prepcallclosemth(L, tbc, status, yy);  /* close variable */
     level = restorestack(L, levelrel);
   }
+  return level;
 }
 
 
diff --git a/src/lfunc.h b/src/lfunc.h
index dc1cebccd1bc..3be265efb584 100644
--- a/src/lfunc.h
+++ b/src/lfunc.h
@@ -29,10 +29,10 @@
 #define MAXUPVAL	255
 
 
-#define upisopen(up)	((up)->v != &(up)->u.value)
+#define upisopen(up)	((up)->v.p != &(up)->u.value)
 
 
-#define uplevel(up)	check_exp(upisopen(up), cast(StkId, (up)->v))
+#define uplevel(up)	check_exp(upisopen(up), cast(StkId, (up)->v.p))
 
 
 /*
@@ -54,7 +54,7 @@ LUAI_FUNC void luaF_initupvals (lua_State *L, LClosure *cl);
 LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
 LUAI_FUNC void luaF_newtbcupval (lua_State *L, StkId level);
 LUAI_FUNC void luaF_closeupval (lua_State *L, StkId level);
-LUAI_FUNC void luaF_close (lua_State *L, StkId level, int status, int yy);
+LUAI_FUNC StkId luaF_close (lua_State *L, StkId level, int status, int yy);
 LUAI_FUNC void luaF_unlinkupval (UpVal *uv);
 LUAI_FUNC void luaF_freeproto (lua_State *L, Proto *f);
 LUAI_FUNC const char *luaF_getlocalname (const Proto *func, int local_number,
diff --git a/src/lgc.c b/src/lgc.c
index 42a73d813acc..a3094ff57126 100644
--- a/src/lgc.c
+++ b/src/lgc.c
@@ -252,12 +252,13 @@ void luaC_fix (lua_State *L, GCObject *o) {
 
 
 /*
-** create a new collectable object (with given type and size) and link
-** it to 'allgc' list.
+** create a new collectable object (with given type, size, and offset)
+** and link it to 'allgc' list.
 */
-GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
+GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
   global_State *g = G(L);
-  GCObject *o = cast(GCObject *, luaM_newobject(L, novariant(tt), sz));
+  char *p = cast_charp(luaM_newobject(L, novariant(tt), sz));
+  GCObject *o = cast(GCObject *, p + offset);
   o->marked = luaC_white(g);
   o->tt = tt;
   o->next = g->allgc;
@@ -265,6 +266,11 @@ GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
   return o;
 }
 
+
+GCObject *luaC_newobj (lua_State *L, int tt, size_t sz) {
+  return luaC_newobjdt(L, tt, sz, 0);
+}
+
 /* }====================================================== */
 
 
@@ -301,7 +307,7 @@ static void reallymarkobject (global_State *g, GCObject *o) {
         set2gray(uv);  /* open upvalues are kept gray */
       else
         set2black(uv);  /* closed upvalues are visited here */
-      markvalue(g, uv->v);  /* mark its content */
+      markvalue(g, uv->v.p);  /* mark its content */
       break;
     }
     case LUA_VUSERDATA: {
@@ -376,7 +382,7 @@ static int remarkupvals (global_State *g) {
         work++;
         if (!iswhite(uv)) {  /* upvalue already visited? */
           lua_assert(upisopen(uv) && isgray(uv));
-          markvalue(g, uv->v);  /* mark its value */
+          markvalue(g, uv->v.p);  /* mark its value */
         }
       }
     }
@@ -620,19 +626,19 @@ static int traverseLclosure (global_State *g, LClosure *cl) {
 */
 static int traversethread (global_State *g, lua_State *th) {
   UpVal *uv;
-  StkId o = th->stack;
+  StkId o = th->stack.p;
   if (isold(th) || g->gcstate == GCSpropagate)
     linkgclist(th, g->grayagain);  /* insert into 'grayagain' list */
   if (o == NULL)
     return 1;  /* stack not completely built yet */
   lua_assert(g->gcstate == GCSatomic ||
              th->openupval == NULL || isintwups(th));
-  for (; o < th->top; o++)  /* mark live elements in the stack */
+  for (; o < th->top.p; o++)  /* mark live elements in the stack */
     markvalue(g, s2v(o));
   for (uv = th->openupval; uv != NULL; uv = uv->u.open.next)
     markobject(g, uv);  /* open upvalues cannot be collected */
   if (g->gcstate == GCSatomic) {  /* final traversal? */
-    for (; o < th->stack_last + EXTRA_STACK; o++)
+    for (; o < th->stack_last.p + EXTRA_STACK; o++)
       setnilvalue(s2v(o));  /* clear dead stack slice */
     /* 'remarkupvals' may have removed thread from 'twups' list */
     if (!isintwups(th) && th->openupval != NULL) {
@@ -892,7 +898,7 @@ static GCObject *udata2finalize (global_State *g) {
 
 static void dothecall (lua_State *L, void *ud) {
   UNUSED(ud);
-  luaD_callnoyield(L, L->top - 2, 0);
+  luaD_callnoyield(L, L->top.p - 2, 0);
 }
 
 
@@ -909,16 +915,16 @@ static void GCTM (lua_State *L) {
     int oldgcstp  = g->gcstp;
     g->gcstp |= GCSTPGC;  /* avoid GC steps */
     L->allowhook = 0;  /* stop debug hooks during GC metamethod */
-    setobj2s(L, L->top++, tm);  /* push finalizer... */
-    setobj2s(L, L->top++, &v);  /* ... and its argument */
+    setobj2s(L, L->top.p++, tm);  /* push finalizer... */
+    setobj2s(L, L->top.p++, &v);  /* ... and its argument */
     L->ci->callstatus |= CIST_FIN;  /* will run a finalizer */
-    status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top - 2), 0);
+    status = luaD_pcall(L, dothecall, NULL, savestack(L, L->top.p - 2), 0);
     L->ci->callstatus &= ~CIST_FIN;  /* not running a finalizer anymore */
     L->allowhook = oldah;  /* restore hooks */
     g->gcstp = oldgcstp;  /* restore state */
     if (l_unlikely(status != LUA_OK)) {  /* error while running __gc? */
       luaE_warnerror(L, "__gc");
-      L->top--;  /* pops error object */
+      L->top.p--;  /* pops error object */
     }
   }
 }
@@ -1041,7 +1047,25 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
 ** =======================================================
 */
 
-static void setpause (global_State *g);
+
+/*
+** Set the "time" to wait before starting a new GC cycle; cycle will
+** start when memory use hits the threshold of ('estimate' * pause /
+** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero,
+** because Lua cannot even start with less than PAUSEADJ bytes).
+*/
+static void setpause (global_State *g) {
+  l_mem threshold, debt;
+  int pause = getgcparam(g->gcpause);
+  l_mem estimate = g->GCestimate / PAUSEADJ;  /* adjust 'estimate' */
+  lua_assert(estimate > 0);
+  threshold = (pause < MAX_LMEM / estimate)  /* overflow? */
+            ? estimate * pause  /* no overflow */
+            : MAX_LMEM;  /* overflow; truncate to maximum */
+  debt = gettotalbytes(g) - threshold;
+  if (debt > 0) debt = 0;
+  luaE_setdebt(g, debt);
+}
 
 
 /*
@@ -1286,6 +1310,15 @@ static void atomic2gen (lua_State *L, global_State *g) {
 
 
 /*
+** Set debt for the next minor collection, which will happen when
+** memory grows 'genminormul'%.
+*/
+static void setminordebt (global_State *g) {
+  luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul));
+}
+
+
+/*
 ** Enter generational mode. Must go until the end of an atomic cycle
 ** to ensure that all objects are correctly marked and weak tables
 ** are cleared. Then, turn all objects into old and finishes the
@@ -1297,6 +1330,7 @@ static lu_mem entergen (lua_State *L, global_State *g) {
   luaC_runtilstate(L, bitmask(GCSpropagate));  /* start new cycle */
   numobjs = atomic(L);  /* propagates all and then do the atomic stuff */
   atomic2gen(L, g);
+  setminordebt(g);  /* set debt assuming next cycle will be minor */
   return numobjs;
 }
 
@@ -1343,15 +1377,6 @@ static lu_mem fullgen (lua_State *L, global_State *g) {
 
 
 /*
-** Set debt for the next minor collection, which will happen when
-** memory grows 'genminormul'%.
-*/
-static void setminordebt (global_State *g) {
-  luaE_setdebt(g, -(cast(l_mem, (gettotalbytes(g) / 100)) * g->genminormul));
-}
-
-
-/*
 ** Does a major collection after last collection was a "bad collection".
 **
 ** When the program is building a big structure, it allocates lots of
@@ -1422,8 +1447,8 @@ static void genstep (lua_State *L, global_State *g) {
       lu_mem numobjs = fullgen(L, g);  /* do a major collection */
       if (gettotalbytes(g) < majorbase + (majorinc / 2)) {
         /* collected at least half of memory growth since last major
-           collection; keep doing minor collections */
-        setminordebt(g);
+           collection; keep doing minor collections. */
+        lua_assert(g->lastatomic == 0);
       }
       else {  /* bad collection */
         g->lastatomic = numobjs;  /* signal that last collection was bad */
@@ -1450,26 +1475,6 @@ static void genstep (lua_State *L, global_State *g) {
 
 
 /*
-** Set the "time" to wait before starting a new GC cycle; cycle will
-** start when memory use hits the threshold of ('estimate' * pause /
-** PAUSEADJ). (Division by 'estimate' should be OK: it cannot be zero,
-** because Lua cannot even start with less than PAUSEADJ bytes).
-*/
-static void setpause (global_State *g) {
-  l_mem threshold, debt;
-  int pause = getgcparam(g->gcpause);
-  l_mem estimate = g->GCestimate / PAUSEADJ;  /* adjust 'estimate' */
-  lua_assert(estimate > 0);
-  threshold = (pause < MAX_LMEM / estimate)  /* overflow? */
-            ? estimate * pause  /* no overflow */
-            : MAX_LMEM;  /* overflow; truncate to maximum */
-  debt = gettotalbytes(g) - threshold;
-  if (debt > 0) debt = 0;
-  luaE_setdebt(g, debt);
-}
-
-
-/*
 ** Enter first sweep phase.
 ** The call to 'sweeptolive' makes the pointer point to an object
 ** inside the list (instead of to the header), so that the real sweep do
@@ -1676,12 +1681,15 @@ static void incstep (lua_State *L, global_State *g) {
 }
 
 /*
-** performs a basic GC step if collector is running
+** Performs a basic GC step if collector is running. (If collector is
+** not running, set a reasonable debt to avoid it being called at
+** every single check.)
 */
 void luaC_step (lua_State *L) {
   global_State *g = G(L);
-  lua_assert(!g->gcemergency);
-  if (gcrunning(g)) {  /* running? */
+  if (!gcrunning(g))  /* not running? */
+    luaE_setdebt(g, -2000);
+  else {
     if(isdecGCmodegen(g))
       genstep(L, g);
     else
diff --git a/src/lgc.h b/src/lgc.h
index 4a125634b9ea..538f6edcccf2 100644
--- a/src/lgc.h
+++ b/src/lgc.h
@@ -172,24 +172,27 @@
 #define luaC_checkGC(L)		luaC_condGC(L,(void)0,(void)0)
 
 
-#define luaC_barrier(L,p,v) (  \
-	(iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ?  \
-	luaC_barrier_(L,obj2gco(p),gcvalue(v)) : cast_void(0))
-
-#define luaC_barrierback(L,p,v) (  \
-	(iscollectable(v) && isblack(p) && iswhite(gcvalue(v))) ? \
-	luaC_barrierback_(L,p) : cast_void(0))
-
 #define luaC_objbarrier(L,p,o) (  \
 	(isblack(p) && iswhite(o)) ? \
 	luaC_barrier_(L,obj2gco(p),obj2gco(o)) : cast_void(0))
 
+#define luaC_barrier(L,p,v) (  \
+	iscollectable(v) ? luaC_objbarrier(L,p,gcvalue(v)) : cast_void(0))
+
+#define luaC_objbarrierback(L,p,o) (  \
+	(isblack(p) && iswhite(o)) ? luaC_barrierback_(L,p) : cast_void(0))
+
+#define luaC_barrierback(L,p,v) (  \
+	iscollectable(v) ? luaC_objbarrierback(L, p, gcvalue(v)) : cast_void(0))
+
 LUAI_FUNC void luaC_fix (lua_State *L, GCObject *o);
 LUAI_FUNC void luaC_freeallobjects (lua_State *L);
 LUAI_FUNC void luaC_step (lua_State *L);
 LUAI_FUNC void luaC_runtilstate (lua_State *L, int statesmask);
 LUAI_FUNC void luaC_fullgc (lua_State *L, int isemergency);
 LUAI_FUNC GCObject *luaC_newobj (lua_State *L, int tt, size_t sz);
+LUAI_FUNC GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz,
+                                                 size_t offset);
 LUAI_FUNC void luaC_barrier_ (lua_State *L, GCObject *o, GCObject *v);
 LUAI_FUNC void luaC_barrierback_ (lua_State *L, GCObject *o);
 LUAI_FUNC void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt);
diff --git a/src/llex.c b/src/llex.c
index e99151787a63..5fc39a5cdec1 100644
--- a/src/llex.c
+++ b/src/llex.c
@@ -128,7 +128,7 @@ l_noret luaX_syntaxerror (LexState *ls, const char *msg) {
 ** ensuring there is only one copy of each unique string.  The table
 ** here is used as a set: the string enters as the key, while its value
 ** is irrelevant. We use the string itself as the value only because it
-** is a TValue readly available. Later, the code generation can change
+** is a TValue readily available. Later, the code generation can change
 ** this value.
 */
 TString *luaX_newstring (LexState *ls, const char *str, size_t l) {
@@ -138,12 +138,12 @@ TString *luaX_newstring (LexState *ls, const char *str, size_t l) {
   if (!ttisnil(o))  /* string already present? */
     ts = keystrval(nodefromval(o));  /* get saved copy */
   else {  /* not in use yet */
-    TValue *stv = s2v(L->top++);  /* reserve stack space for string */
+    TValue *stv = s2v(L->top.p++);  /* reserve stack space for string */
     setsvalue(L, stv, ts);  /* temporarily anchor the string */
     luaH_finishset(L, ls->h, stv, o, stv);  /* t[string] = string */
     /* table is not a metatable, so it does not need to invalidate cache */
     luaC_checkGC(L);
-    L->top--;  /* remove string from stack */
+    L->top.p--;  /* remove string from stack */
   }
   return ts;
 }
diff --git a/src/llimits.h b/src/llimits.h
index 52a32f92e302..1c826f7be205 100644
--- a/src/llimits.h
+++ b/src/llimits.h
@@ -71,11 +71,24 @@ typedef signed char ls_byte;
 
 
 /*
-** conversion of pointer to unsigned integer:
-** this is for hashing only; there is no problem if the integer
-** cannot hold the whole pointer value
+** conversion of pointer to unsigned integer: this is for hashing only;
+** there is no problem if the integer cannot hold the whole pointer
+** value. (In strict ISO C this may cause undefined behavior, but no
+** actual machine seems to bother.)
 */
-#define point2uint(p)	((unsigned int)((size_t)(p) & UINT_MAX))
+#if !defined(LUA_USE_C89) && defined(__STDC_VERSION__) && \
+    __STDC_VERSION__ >= 199901L
+#include <stdint.h>
+#if defined(UINTPTR_MAX)  /* even in C99 this type is optional */
+#define L_P2I	uintptr_t
+#else  /* no 'intptr'? */
+#define L_P2I	uintmax_t  /* use the largest available integer */
+#endif
+#else  /* C89 option */
+#define L_P2I	size_t
+#endif
+
+#define point2uint(p)	((unsigned int)((L_P2I)(p) & UINT_MAX))
 
 
 
diff --git a/src/lmathlib.c b/src/lmathlib.c
index e0c61a168d98..d0b1e1e5d6f5 100644
--- a/src/lmathlib.c
+++ b/src/lmathlib.c
@@ -267,7 +267,7 @@ static int math_type (lua_State *L) {
 
 /* try to find an integer type with at least 64 bits */
 
-#if (ULONG_MAX >> 31 >> 31) >= 3
+#if ((ULONG_MAX >> 31) >> 31) >= 3
 
 /* 'long' has at least 64 bits */
 #define Rand64		unsigned long
@@ -277,9 +277,9 @@ static int math_type (lua_State *L) {
 /* there is a 'long long' type (which must have at least 64 bits) */
 #define Rand64		unsigned long long
 
-#elif (LUA_MAXUNSIGNED >> 31 >> 31) >= 3
+#elif ((LUA_MAXUNSIGNED >> 31) >> 31) >= 3
 
-/* 'lua_Integer' has at least 64 bits */
+/* 'lua_Unsigned' has at least 64 bits */
 #define Rand64		lua_Unsigned
 
 #endif
@@ -500,12 +500,12 @@ static lua_Number I2d (Rand64 x) {
 
 /* convert a 'Rand64' to a 'lua_Unsigned' */
 static lua_Unsigned I2UInt (Rand64 x) {
-  return ((lua_Unsigned)trim32(x.h) << 31 << 1) | (lua_Unsigned)trim32(x.l);
+  return (((lua_Unsigned)trim32(x.h) << 31) << 1) | (lua_Unsigned)trim32(x.l);
 }
 
 /* convert a 'lua_Unsigned' to a 'Rand64' */
 static Rand64 Int2I (lua_Unsigned n) {
-  return packI((lu_int32)(n >> 31 >> 1), (lu_int32)n);
+  return packI((lu_int32)((n >> 31) >> 1), (lu_int32)n);
 }
 
 #endif  /* } */
diff --git a/src/lmem.c b/src/lmem.c
index 9029d588c12e..9800a86fc024 100644
--- a/src/lmem.c
+++ b/src/lmem.c
@@ -22,25 +22,6 @@
 #include "lstate.h"
 
 
-#if defined(EMERGENCYGCTESTS)
-/*
-** First allocation will fail whenever not building initial state.
-** (This fail will trigger 'tryagain' and a full GC cycle at every
-** allocation.)
-*/
-static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
-  if (completestate(g) && ns > 0)  /* frees never fail */
-    return NULL;  /* fail */
-  else  /* normal allocation */
-    return (*g->frealloc)(g->ud, block, os, ns);
-}
-#else
-#define firsttry(g,block,os,ns)    ((*g->frealloc)(g->ud, block, os, ns))
-#endif
-
-
-
-
 
 /*
 ** About the realloc function:
@@ -60,6 +41,43 @@ static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
 */
 
 
+/*
+** Macro to call the allocation function.
+*/
+#define callfrealloc(g,block,os,ns)    ((*g->frealloc)(g->ud, block, os, ns))
+
+
+/*
+** When an allocation fails, it will try again after an emergency
+** collection, except when it cannot run a collection.  The GC should
+** not be called while the state is not fully built, as the collector
+** is not yet fully initialized. Also, it should not be called when
+** 'gcstopem' is true, because then the interpreter is in the middle of
+** a collection step.
+*/
+#define cantryagain(g)	(completestate(g) && !g->gcstopem)
+
+
+
+
+#if defined(EMERGENCYGCTESTS)
+/*
+** First allocation will fail except when freeing a block (frees never
+** fail) and when it cannot try again; this fail will trigger 'tryagain'
+** and a full GC cycle at every allocation.
+*/
+static void *firsttry (global_State *g, void *block, size_t os, size_t ns) {
+  if (ns > 0 && cantryagain(g))
+    return NULL;  /* fail */
+  else  /* normal allocation */
+    return callfrealloc(g, block, os, ns);
+}
+#else
+#define firsttry(g,block,os,ns)    callfrealloc(g, block, os, ns)
+#endif
+
+
+
 
 
 /*
@@ -132,7 +150,7 @@ l_noret luaM_toobig (lua_State *L) {
 void luaM_free_ (lua_State *L, void *block, size_t osize) {
   global_State *g = G(L);
   lua_assert((osize == 0) == (block == NULL));
-  (*g->frealloc)(g->ud, block, osize, 0);
+  callfrealloc(g, block, osize, 0);
   g->GCdebt -= osize;
 }
 
@@ -140,19 +158,15 @@ void luaM_free_ (lua_State *L, void *block, size_t osize) {
 /*
 ** In case of allocation fail, this function will do an emergency
 ** collection to free some memory and then try the allocation again.
-** The GC should not be called while state is not fully built, as the
-** collector is not yet fully initialized. Also, it should not be called
-** when 'gcstopem' is true, because then the interpreter is in the
-** middle of a collection step.
 */
 static void *tryagain (lua_State *L, void *block,
                        size_t osize, size_t nsize) {
   global_State *g = G(L);
-  if (completestate(g) && !g->gcstopem) {
+  if (cantryagain(g)) {
     luaC_fullgc(L, 1);  /* try to free some memory... */
-    return (*g->frealloc)(g->ud, block, osize, nsize);  /* try again */
+    return callfrealloc(g, block, osize, nsize);  /* try again */
   }
-  else return NULL;  /* cannot free any memory without a full state */
+  else return NULL;  /* cannot run an emergency collection */
 }
 
 
diff --git a/src/loadlib.c b/src/loadlib.c
index 6f9fa37366e4..d792dffaa03b 100644
--- a/src/loadlib.c
+++ b/src/loadlib.c
@@ -708,8 +708,13 @@ static const luaL_Reg ll_funcs[] = {
 
 
 static void createsearcherstable (lua_State *L) {
-  static const lua_CFunction searchers[] =
-    {searcher_preload, searcher_Lua, searcher_C, searcher_Croot, NULL};
+  static const lua_CFunction searchers[] = {
+    searcher_preload,
+    searcher_Lua,
+    searcher_C,
+    searcher_Croot,
+    NULL
+  };
   int i;
   /* create 'searchers' table */
   lua_createtable(L, sizeof(searchers)/sizeof(searchers[0]) - 1, 0);
diff --git a/src/lobject.c b/src/lobject.c
index 301aa900be0a..f73ffc6d92bd 100644
--- a/src/lobject.c
+++ b/src/lobject.c
@@ -62,7 +62,7 @@ static lua_Integer intarith (lua_State *L, int op, lua_Integer v1,
     case LUA_OPBOR: return intop(|, v1, v2);
     case LUA_OPBXOR: return intop(^, v1, v2);
     case LUA_OPSHL: return luaV_shiftl(v1, v2);
-    case LUA_OPSHR: return luaV_shiftl(v1, -v2);
+    case LUA_OPSHR: return luaV_shiftr(v1, v2);
     case LUA_OPUNM: return intop(-, 0, v1);
     case LUA_OPBNOT: return intop(^, ~l_castS2U(0), v1);
     default: lua_assert(0); return 0;
@@ -386,29 +386,39 @@ void luaO_tostring (lua_State *L, TValue *obj) {
 ** ===================================================================
 */
 
-/* size for buffer space used by 'luaO_pushvfstring' */
-#define BUFVFS		200
+/*
+** Size for buffer space used by 'luaO_pushvfstring'. It should be
+** (LUA_IDSIZE + MAXNUMBER2STR) + a minimal space for basic messages,
+** so that 'luaG_addinfo' can work directly on the buffer.
+*/
+#define BUFVFS		(LUA_IDSIZE + MAXNUMBER2STR + 95)
 
 /* buffer used by 'luaO_pushvfstring' */
 typedef struct BuffFS {
   lua_State *L;
-  int pushed;  /* number of string pieces already on the stack */
+  int pushed;  /* true if there is a part of the result on the stack */
   int blen;  /* length of partial string in 'space' */
   char space[BUFVFS];  /* holds last part of the result */
 } BuffFS;
 
 
 /*
-** Push given string to the stack, as part of the buffer, and
-** join the partial strings in the stack into one.
+** Push given string to the stack, as part of the result, and
+** join it to previous partial result if there is one.
+** It may call 'luaV_concat' while using one slot from EXTRA_STACK.
+** This call cannot invoke metamethods, as both operands must be
+** strings. It can, however, raise an error if the result is too
+** long. In that case, 'luaV_concat' frees the extra slot before
+** raising the error.
 */
-static void pushstr (BuffFS *buff, const char *str, size_t l) {
+static void pushstr (BuffFS *buff, const char *str, size_t lstr) {
   lua_State *L = buff->L;
-  setsvalue2s(L, L->top, luaS_newlstr(L, str, l));
-  L->top++;  /* may use one extra slot */
-  buff->pushed++;
-  luaV_concat(L, buff->pushed);  /* join partial results into one */
-  buff->pushed = 1;
+  setsvalue2s(L, L->top.p, luaS_newlstr(L, str, lstr));
+  L->top.p++;  /* may use one slot from EXTRA_STACK */
+  if (!buff->pushed)  /* no previous string on the stack? */
+    buff->pushed = 1;  /* now there is one */
+  else  /* join previous string with new one */
+    luaV_concat(L, 2);
 }
 
 
@@ -454,7 +464,7 @@ static void addstr2buff (BuffFS *buff, const char *str, size_t slen) {
 
 
 /*
-** Add a number to the buffer.
+** Add a numeral to the buffer.
 */
 static void addnum2buff (BuffFS *buff, TValue *num) {
   char *numbuff = getbuff(buff, MAXNUMBER2STR);
@@ -532,7 +542,7 @@ const char *luaO_pushvfstring (lua_State *L, const char *fmt, va_list argp) {
   addstr2buff(&buff, fmt, strlen(fmt));  /* rest of 'fmt' */
   clearbuff(&buff);  /* empty buffer into the stack */
   lua_assert(buff.pushed == 1);
-  return svalue(s2v(L->top - 1));
+  return svalue(s2v(L->top.p - 1));
 }
 
 
diff --git a/src/lobject.h b/src/lobject.h
index 0e05b3e42ea9..556608e4aa21 100644
--- a/src/lobject.h
+++ b/src/lobject.h
@@ -52,6 +52,8 @@ typedef union Value {
   lua_CFunction f; /* light C functions */
   lua_Integer i;   /* integer numbers */
   lua_Number n;    /* float numbers */
+  /* not used, but may avoid warnings for uninitialized value */
+  lu_byte ub;
 } Value;
 
 
@@ -155,6 +157,17 @@ typedef union StackValue {
 /* index to stack elements */
 typedef StackValue *StkId;
 
+
+/*
+** When reallocating the stack, change all pointers to the stack into
+** proper offsets.
+*/
+typedef union {
+  StkId p;  /* actual pointer */
+  ptrdiff_t offset;  /* used while the stack is being reallocated */
+} StkIdRel;
+
+
 /* convert a 'StackValue' to a 'TValue' */
 #define s2v(o)	(&(o)->val)
 
@@ -615,8 +628,10 @@ typedef struct Proto {
 */
 typedef struct UpVal {
   CommonHeader;
-  lu_byte tbc;  /* true if it represents a to-be-closed variable */
-  TValue *v;  /* points to stack or to its own value */
+  union {
+    TValue *p;  /* points to stack or to its own value */
+    ptrdiff_t offset;  /* used while the stack is being reallocated */
+  } v;
   union {
     struct {  /* (when open) */
       struct UpVal *next;  /* linked list */
diff --git a/src/lopcodes.h b/src/lopcodes.h
index 7c2745159606..4c55145399ff 100644
--- a/src/lopcodes.h
+++ b/src/lopcodes.h
@@ -21,7 +21,7 @@ iABC          C(8)     |      B(8)     |k|     A(8)      |   Op(7)     |
 iABx                Bx(17)               |     A(8)      |   Op(7)     |
 iAsBx              sBx (signed)(17)      |     A(8)      |   Op(7)     |
 iAx                           Ax(25)                     |   Op(7)     |
-isJ                           sJ(25)                     |   Op(7)     |
+isJ                           sJ (signed)(25)            |   Op(7)     |
 
   A signed argument is represented in excess K: the represented value is
   the written unsigned value minus K, where K is half the maximum for the
diff --git a/src/loslib.c b/src/loslib.c
index 3e20d622bacd..ad5a92768852 100644
--- a/src/loslib.c
+++ b/src/loslib.c
@@ -30,23 +30,14 @@
 */
 #if !defined(LUA_STRFTIMEOPTIONS)	/* { */
 
-/* options for ANSI C 89 (only 1-char options) */
-#define L_STRFTIMEC89		"aAbBcdHIjmMpSUwWxXyYZ%"
-
-/* options for ISO C 99 and POSIX */
-#define L_STRFTIMEC99 "aAbBcCdDeFgGhHIjmMnprRStTuUVwWxXyYzZ%" \
-    "||" "EcECExEXEyEY" "OdOeOHOIOmOMOSOuOUOVOwOWOy"  /* two-char options */
-
-/* options for Windows */
-#define L_STRFTIMEWIN "aAbBcdHIjmMpSUwWxXyYzZ%" \
-    "||" "#c#x#d#H#I#j#m#M#S#U#w#W#y#Y"  /* two-char options */
-
 #if defined(LUA_USE_WINDOWS)
-#define LUA_STRFTIMEOPTIONS	L_STRFTIMEWIN
-#elif defined(LUA_USE_C89)
-#define LUA_STRFTIMEOPTIONS	L_STRFTIMEC89
+#define LUA_STRFTIMEOPTIONS  "aAbBcdHIjmMpSUwWxXyYzZ%" \
+    "||" "#c#x#d#H#I#j#m#M#S#U#w#W#y#Y"  /* two-char options */
+#elif defined(LUA_USE_C89)  /* ANSI C 89 (only 1-char options) */
+#define LUA_STRFTIMEOPTIONS  "aAbBcdHIjmMpSUwWxXyYZ%"
 #else  /* C99 specification */
-#define LUA_STRFTIMEOPTIONS	L_STRFTIMEC99
+#define LUA_STRFTIMEOPTIONS  "aAbBcCdDeFgGhHIjmMnprRStTuUVwWxXyYzZ%" \
+    "||" "EcECExEXEyEY" "OdOeOHOIOmOMOSOuOUOVOwOWOy"  /* two-char options */
 #endif
 
 #endif					/* } */
@@ -138,12 +129,21 @@
 /* }================================================================== */
 
 
+#if !defined(l_system)
+#if defined(LUA_USE_IOS)
+/* Despite claiming to be ISO C, iOS does not implement 'system'. */
+#define l_system(cmd) ((cmd) == NULL ? 0 : -1)
+#else
+#define l_system(cmd)	system(cmd)  /* default definition */
+#endif
+#endif
+
 
 static int os_execute (lua_State *L) {
   const char *cmd = luaL_optstring(L, 1, NULL);
   int stat;
   errno = 0;
-  stat = system(cmd);
+  stat = l_system(cmd);
   if (cmd != NULL)
     return luaL_execresult(L, stat);
   else {
@@ -260,9 +260,7 @@ static int getfield (lua_State *L, const char *key, int d, int delta) {
     res = d;
   }
   else {
-    /* unsigned avoids overflow when lua_Integer has 32 bits */
-    if (!(res >= 0 ? (lua_Unsigned)res <= (lua_Unsigned)INT_MAX + delta
-                   : (lua_Integer)INT_MIN + delta <= res))
+    if (!(res >= 0 ? res - delta <= INT_MAX : INT_MIN + delta <= res))
       return luaL_error(L, "field '%s' is out-of-bound", key);
     res -= delta;
   }
diff --git a/src/lparser.c b/src/lparser.c
index 3abe3d75187b..b745f236f068 100644
--- a/src/lparser.c
+++ b/src/lparser.c
@@ -468,6 +468,7 @@ static void singlevar (LexState *ls, expdesc *var) {
     expdesc key;
     singlevaraux(fs, ls->envn, var, 1);  /* get environment variable */
     lua_assert(var->k != VVOID);  /* this one must exist */
+    luaK_exp2anyregup(fs, var);  /* but could be a constant */
     codestring(&key, varname);  /* key is variable name */
     luaK_indexed(fs, var, &key);  /* env[varname] */
   }
@@ -520,12 +521,12 @@ static l_noret jumpscopeerror (LexState *ls, Labeldesc *gt) {
 
 /*
 ** Solves the goto at index 'g' to given 'label' and removes it
-** from the list of pending goto's.
+** from the list of pending gotos.
 ** If it jumps into the scope of some variable, raises an error.
 */
 static void solvegoto (LexState *ls, int g, Labeldesc *label) {
   int i;
-  Labellist *gl = &ls->dyd->gt;  /* list of goto's */
+  Labellist *gl = &ls->dyd->gt;  /* list of gotos */
   Labeldesc *gt = &gl->arr[g];  /* goto to be resolved */
   lua_assert(eqstr(gt->name, label->name));
   if (l_unlikely(gt->nactvar < label->nactvar))  /* enter some scope? */
@@ -579,7 +580,7 @@ static int newgotoentry (LexState *ls, TString *name, int line, int pc) {
 /*
 ** Solves forward jumps. Check whether new label 'lb' matches any
 ** pending gotos in current block and solves them. Return true
-** if any of the goto's need to close upvalues.
+** if any of the gotos need to close upvalues.
 */
 static int solvegotos (LexState *ls, Labeldesc *lb) {
   Labellist *gl = &ls->dyd->gt;
@@ -600,7 +601,7 @@ static int solvegotos (LexState *ls, Labeldesc *lb) {
 /*
 ** Create a new label with the given 'name' at the given 'line'.
 ** 'last' tells whether label is the last non-op statement in its
-** block. Solves all pending goto's to this new label and adds
+** block. Solves all pending gotos to this new label and adds
 ** a close instruction if necessary.
 ** Returns true iff it added a close instruction.
 */
@@ -673,19 +674,19 @@ static void leaveblock (FuncState *fs) {
   LexState *ls = fs->ls;
   int hasclose = 0;
   int stklevel = reglevel(fs, bl->nactvar);  /* level outside the block */
-  if (bl->isloop)  /* fix pending breaks? */
+  removevars(fs, bl->nactvar);  /* remove block locals */
+  lua_assert(bl->nactvar == fs->nactvar);  /* back to level on entry */
+  if (bl->isloop)  /* has to fix pending breaks? */
     hasclose = createlabel(ls, luaS_newliteral(ls->L, "break"), 0, 0);
-  if (!hasclose && bl->previous && bl->upval)
+  if (!hasclose && bl->previous && bl->upval)  /* still need a 'close'? */
     luaK_codeABC(fs, OP_CLOSE, stklevel, 0, 0);
-  fs->bl = bl->previous;
-  removevars(fs, bl->nactvar);
-  lua_assert(bl->nactvar == fs->nactvar);
   fs->freereg = stklevel;  /* free registers */
   ls->dyd->label.n = bl->firstlabel;  /* remove local labels */
-  if (bl->previous)  /* inner block? */
-    movegotosout(fs, bl);  /* update pending gotos to outer block */
+  fs->bl = bl->previous;  /* current block now is previous one */
+  if (bl->previous)  /* was it a nested block? */
+    movegotosout(fs, bl);  /* update pending gotos to enclosing block */
   else {
-    if (bl->firstgoto < ls->dyd->gt.n)  /* pending gotos in outer block? */
+    if (bl->firstgoto < ls->dyd->gt.n)  /* still pending gotos? */
       undefgoto(ls, &ls->dyd->gt.arr[bl->firstgoto]);  /* error */
   }
 }
@@ -1943,10 +1944,10 @@ LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
   LexState lexstate;
   FuncState funcstate;
   LClosure *cl = luaF_newLclosure(L, 1);  /* create main closure */
-  setclLvalue2s(L, L->top, cl);  /* anchor it (to avoid being collected) */
+  setclLvalue2s(L, L->top.p, cl);  /* anchor it (to avoid being collected) */
   luaD_inctop(L);
   lexstate.h = luaH_new(L);  /* create table for scanner */
-  sethvalue2s(L, L->top, lexstate.h);  /* anchor it */
+  sethvalue2s(L, L->top.p, lexstate.h);  /* anchor it */
   luaD_inctop(L);
   funcstate.f = cl->p = luaF_newproto(L);
   luaC_objbarrier(L, cl, cl->p);
@@ -1960,7 +1961,7 @@ LClosure *luaY_parser (lua_State *L, ZIO *z, Mbuffer *buff,
   lua_assert(!funcstate.prev && funcstate.nups == 1 && !lexstate.fs);
   /* all scopes should be correctly finished */
   lua_assert(dyd->actvar.n == 0 && dyd->gt.n == 0 && dyd->label.n == 0);
-  L->top--;  /* remove scanner's table */
+  L->top.p--;  /* remove scanner's table */
   return cl;  /* closure is on the stack, too */
 }
 
diff --git a/src/lstate.c b/src/lstate.c
index 1ffe1a0f71cd..1e925e5ad4cb 100644
--- a/src/lstate.c
+++ b/src/lstate.c
@@ -180,33 +180,33 @@ LUAI_FUNC void luaE_incCstack (lua_State *L) {
 static void stack_init (lua_State *L1, lua_State *L) {
   int i; CallInfo *ci;
   /* initialize stack array */
-  L1->stack = luaM_newvector(L, BASIC_STACK_SIZE + EXTRA_STACK, StackValue);
-  L1->tbclist = L1->stack;
+  L1->stack.p = luaM_newvector(L, BASIC_STACK_SIZE + EXTRA_STACK, StackValue);
+  L1->tbclist.p = L1->stack.p;
   for (i = 0; i < BASIC_STACK_SIZE + EXTRA_STACK; i++)
-    setnilvalue(s2v(L1->stack + i));  /* erase new stack */
-  L1->top = L1->stack;
-  L1->stack_last = L1->stack + BASIC_STACK_SIZE;
+    setnilvalue(s2v(L1->stack.p + i));  /* erase new stack */
+  L1->top.p = L1->stack.p;
+  L1->stack_last.p = L1->stack.p + BASIC_STACK_SIZE;
   /* initialize first ci */
   ci = &L1->base_ci;
   ci->next = ci->previous = NULL;
   ci->callstatus = CIST_C;
-  ci->func = L1->top;
+  ci->func.p = L1->top.p;
   ci->u.c.k = NULL;
   ci->nresults = 0;
-  setnilvalue(s2v(L1->top));  /* 'function' entry for this 'ci' */
-  L1->top++;
-  ci->top = L1->top + LUA_MINSTACK;
+  setnilvalue(s2v(L1->top.p));  /* 'function' entry for this 'ci' */
+  L1->top.p++;
+  ci->top.p = L1->top.p + LUA_MINSTACK;
   L1->ci = ci;
 }
 
 
 static void freestack (lua_State *L) {
-  if (L->stack == NULL)
+  if (L->stack.p == NULL)
     return;  /* stack not completely built yet */
   L->ci = &L->base_ci;  /* free the entire 'ci' list */
   luaE_freeCI(L);
   lua_assert(L->nci == 0);
-  luaM_freearray(L, L->stack, stacksize(L) + EXTRA_STACK);  /* free stack */
+  luaM_freearray(L, L->stack.p, stacksize(L) + EXTRA_STACK);  /* free stack */
 }
 
 
@@ -248,7 +248,7 @@ static void f_luaopen (lua_State *L, void *ud) {
 */
 static void preinit_thread (lua_State *L, global_State *g) {
   G(L) = g;
-  L->stack = NULL;
+  L->stack.p = NULL;
   L->ci = NULL;
   L->nci = 0;
   L->twups = L;  /* thread has no upvalues */
@@ -284,20 +284,16 @@ static void close_state (lua_State *L) {
 
 
 LUA_API lua_State *lua_newthread (lua_State *L) {
-  global_State *g;
+  global_State *g = G(L);
+  GCObject *o;
   lua_State *L1;
   lua_lock(L);
-  g = G(L);
   luaC_checkGC(L);
   /* create new thread */
-  L1 = &cast(LX *, luaM_newobject(L, LUA_TTHREAD, sizeof(LX)))->l;
-  L1->marked = luaC_white(g);
-  L1->tt = LUA_VTHREAD;
-  /* link it on list 'allgc' */
-  L1->next = g->allgc;
-  g->allgc = obj2gco(L1);
+  o = luaC_newobjdt(L, LUA_TTHREAD, sizeof(LX), offsetof(LX, l));
+  L1 = gco2th(o);
   /* anchor it on L stack */
-  setthvalue2s(L, L->top, L1);
+  setthvalue2s(L, L->top.p, L1);
   api_incr_top(L);
   preinit_thread(L1, g);
   L1->hookmask = L->hookmask;
@@ -316,7 +312,7 @@ LUA_API lua_State *lua_newthread (lua_State *L) {
 
 void luaE_freethread (lua_State *L, lua_State *L1) {
   LX *l = fromstate(L1);
-  luaF_closeupval(L1, L1->stack);  /* close all upvalues */
+  luaF_closeupval(L1, L1->stack.p);  /* close all upvalues */
   lua_assert(L1->openupval == NULL);
   luai_userstatefree(L, L1);
   freestack(L1);
@@ -326,32 +322,41 @@ void luaE_freethread (lua_State *L, lua_State *L1) {
 
 int luaE_resetthread (lua_State *L, int status) {
   CallInfo *ci = L->ci = &L->base_ci;  /* unwind CallInfo list */
-  setnilvalue(s2v(L->stack));  /* 'function' entry for basic 'ci' */
-  ci->func = L->stack;
+  setnilvalue(s2v(L->stack.p));  /* 'function' entry for basic 'ci' */
+  ci->func.p = L->stack.p;
   ci->callstatus = CIST_C;
   if (status == LUA_YIELD)
     status = LUA_OK;
   L->status = LUA_OK;  /* so it can run __close metamethods */
   status = luaD_closeprotected(L, 1, status);
   if (status != LUA_OK)  /* errors? */
-    luaD_seterrorobj(L, status, L->stack + 1);
+    luaD_seterrorobj(L, status, L->stack.p + 1);
   else
-    L->top = L->stack + 1;
-  ci->top = L->top + LUA_MINSTACK;
-  luaD_reallocstack(L, cast_int(ci->top - L->stack), 0);
+    L->top.p = L->stack.p + 1;
+  ci->top.p = L->top.p + LUA_MINSTACK;
+  luaD_reallocstack(L, cast_int(ci->top.p - L->stack.p), 0);
   return status;
 }
 
 
-LUA_API int lua_resetthread (lua_State *L) {
+LUA_API int lua_closethread (lua_State *L, lua_State *from) {
   int status;
   lua_lock(L);
+  L->nCcalls = (from) ? getCcalls(from) : 0;
   status = luaE_resetthread(L, L->status);
   lua_unlock(L);
   return status;
 }
 
 
+/*
+** Deprecated! Use 'lua_closethread' instead.
+*/
+LUA_API int lua_resetthread (lua_State *L) {
+  return lua_closethread(L, NULL);
+}
+
+
 LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   int i;
   lua_State *L;
@@ -426,7 +431,7 @@ void luaE_warning (lua_State *L, const char *msg, int tocont) {
 ** Generate a warning from an error message
 */
 void luaE_warnerror (lua_State *L, const char *where) {
-  TValue *errobj = s2v(L->top - 1);  /* error object */
+  TValue *errobj = s2v(L->top.p - 1);  /* error object */
   const char *msg = (ttisstring(errobj))
                   ? svalue(errobj)
                   : "error object is not a string";
diff --git a/src/lstate.h b/src/lstate.h
index 61e82cde7253..8bf6600e3441 100644
--- a/src/lstate.h
+++ b/src/lstate.h
@@ -9,6 +9,11 @@
 
 #include "lua.h"
 
+
+/* Some header files included here need this definition */
+typedef struct CallInfo CallInfo;
+
+
 #include "lobject.h"
 #include "ltm.h"
 #include "lzio.h"
@@ -139,7 +144,7 @@ struct lua_longjmp;  /* defined in ldo.c */
 
 #define BASIC_STACK_SIZE        (2*LUA_MINSTACK)
 
-#define stacksize(th)	cast_int((th)->stack_last - (th)->stack)
+#define stacksize(th)	cast_int((th)->stack_last.p - (th)->stack.p)
 
 
 /* kinds of Garbage Collection */
@@ -169,9 +174,9 @@ typedef struct stringtable {
 ** - field 'transferinfo' is used only during call/returnhooks,
 ** before the function starts or after it ends.
 */
-typedef struct CallInfo {
-  StkId func;  /* function index in the stack */
-  StkId	top;  /* top for this function */
+struct CallInfo {
+  StkIdRel func;  /* function index in the stack */
+  StkIdRel	top;  /* top for this function */
   struct CallInfo *previous, *next;  /* dynamic call link */
   union {
     struct {  /* only for Lua functions */
@@ -196,7 +201,7 @@ typedef struct CallInfo {
   } u2;
   short nresults;  /* expected number of results from this function */
   unsigned short callstatus;
-} CallInfo;
+};
 
 
 /*
@@ -291,7 +296,7 @@ typedef struct global_State {
   struct lua_State *mainthread;
   TString *memerrmsg;  /* message for memory-allocation errors */
   TString *tmname[TM_N];  /* array with tag-method names */
-  struct Table *mt[LUA_NUMTAGS];  /* metatables for basic types */
+  struct Table *mt[LUA_NUMTYPES];  /* metatables for basic types */
   TString *strcache[STRCACHE_N][STRCACHE_M];  /* cache for strings in API */
   lua_WarnFunction warnf;  /* warning function */
   void *ud_warn;         /* auxiliary data to 'warnf' */
@@ -306,13 +311,13 @@ struct lua_State {
   lu_byte status;
   lu_byte allowhook;
   unsigned short nci;  /* number of items in 'ci' list */
-  StkId top;  /* first free slot in the stack */
+  StkIdRel top;  /* first free slot in the stack */
   global_State *l_G;
   CallInfo *ci;  /* call info for current function */
-  StkId stack_last;  /* end of stack (last element + 1) */
-  StkId stack;  /* stack base */
+  StkIdRel stack_last;  /* end of stack (last element + 1) */
+  StkIdRel stack;  /* stack base */
   UpVal *openupval;  /* list of open upvalues in this stack */
-  StkId tbclist;  /* list of to-be-closed variables */
+  StkIdRel tbclist;  /* list of to-be-closed variables */
   GCObject *gclist;
   struct lua_State *twups;  /* list of threads with open upvalues */
   struct lua_longjmp *errorJmp;  /* current error recover point */
diff --git a/src/lstrlib.c b/src/lstrlib.c
index 0b4fdbb7b5bf..03167161df18 100644
--- a/src/lstrlib.c
+++ b/src/lstrlib.c
@@ -570,7 +570,7 @@ static const char *match_capture (MatchState *ms, const char *s, int l) {
 static const char *match (MatchState *ms, const char *s, const char *p) {
   if (l_unlikely(ms->matchdepth-- == 0))
     luaL_error(ms->L, "pattern too complex");
-  init: /* using goto's to optimize tail recursion */
+  init: /* using goto to optimize tail recursion */
   if (p != ms->p_end) {  /* end of pattern? */
     switch (*p) {
       case '(': {  /* start capture */
diff --git a/src/ltable.c b/src/ltable.c
index 1b1cd2415b60..3c690c5f1751 100644
--- a/src/ltable.c
+++ b/src/ltable.c
@@ -107,7 +107,7 @@ static const TValue absentkey = {ABSTKEYCONSTANT};
 */
 static Node *hashint (const Table *t, lua_Integer i) {
   lua_Unsigned ui = l_castS2U(i);
-  if (ui <= (unsigned int)INT_MAX)
+  if (ui <= cast_uint(INT_MAX))
     return hashmod(t, cast_int(ui));
   else
     return hashmod(t, ui);
@@ -257,10 +257,12 @@ LUAI_FUNC unsigned int luaH_realasize (const Table *t) {
     size |= (size >> 2);
     size |= (size >> 4);
     size |= (size >> 8);
+#if (UINT_MAX >> 14) > 3  /* unsigned int has more than 16 bits */
     size |= (size >> 16);
 #if (UINT_MAX >> 30) > 3
     size |= (size >> 32);  /* unsigned int has more than 32 bits */
 #endif
+#endif
     size++;
     lua_assert(ispow2(size) && size/2 < t->alimit && t->alimit < size);
     return size;
@@ -488,7 +490,7 @@ static void setnodevector (lua_State *L, Table *t, unsigned int size) {
       luaG_runerror(L, "table overflow");
     size = twoto(lsize);
     t->node = luaM_newvector(L, size, Node);
-    for (i = 0; i < (int)size; i++) {
+    for (i = 0; i < cast_int(size); i++) {
       Node *n = gnode(t, i);
       gnext(n) = 0;
       setnilkey(n);
@@ -975,6 +977,4 @@ Node *luaH_mainposition (const Table *t, const TValue *key) {
   return mainpositionTV(t, key);
 }
 
-int luaH_isdummy (const Table *t) { return isdummy(t); }
-
 #endif
diff --git a/src/ltable.h b/src/ltable.h
index 7bbbcb213f8b..75dd9e26e015 100644
--- a/src/ltable.h
+++ b/src/ltable.h
@@ -59,7 +59,6 @@ LUAI_FUNC unsigned int luaH_realasize (const Table *t);
 
 #if defined(LUA_DEBUG)
 LUAI_FUNC Node *luaH_mainposition (const Table *t, const TValue *key);
-LUAI_FUNC int luaH_isdummy (const Table *t);
 #endif
 
 
diff --git a/src/ltablib.c b/src/ltablib.c
index 868d78fd83ec..e6bc4d04af47 100644
--- a/src/ltablib.c
+++ b/src/ltablib.c
@@ -93,7 +93,7 @@ static int tremove (lua_State *L) {
   lua_Integer pos = luaL_optinteger(L, 2, size);
   if (pos != size)  /* validate 'pos' if given */
     /* check whether 'pos' is in [1, size + 1] */
-    luaL_argcheck(L, (lua_Unsigned)pos - 1u <= (lua_Unsigned)size, 1,
+    luaL_argcheck(L, (lua_Unsigned)pos - 1u <= (lua_Unsigned)size, 2,
                      "position out of bounds");
   lua_geti(L, 1, pos);  /* result = t[pos] */
   for ( ; pos < size; pos++) {
diff --git a/src/ltests.c b/src/ltests.c
new file mode 100644
index 000000000000..7d184c0d8ee1
--- /dev/null
+++ b/src/ltests.c
@@ -0,0 +1,1977 @@
+/*
+** $Id: ltests.c $
+** Internal Module for Debugging of the Lua Implementation
+** See Copyright Notice in lua.h
+*/
+
+#define ltests_c
+#define LUA_CORE
+
+#include "lprefix.h"
+
+
+#include <limits.h>
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lua.h"
+
+#include "lapi.h"
+#include "lauxlib.h"
+#include "lcode.h"
+#include "lctype.h"
+#include "ldebug.h"
+#include "ldo.h"
+#include "lfunc.h"
+#include "lmem.h"
+#include "lopcodes.h"
+#include "lopnames.h"
+#include "lstate.h"
+#include "lstring.h"
+#include "ltable.h"
+#include "lualib.h"
+
+
+
+/*
+** The whole module only makes sense with LUA_DEBUG on
+*/
+#if defined(LUA_DEBUG)
+
+
+void *l_Trick = 0;
+
+
+#define obj_at(L,k)	s2v(L->ci->func.p + (k))
+
+
+static int runC (lua_State *L, lua_State *L1, const char *pc);
+
+
+static void setnameval (lua_State *L, const char *name, int val) {
+  lua_pushinteger(L, val);
+  lua_setfield(L, -2, name);
+}
+
+
+static void pushobject (lua_State *L, const TValue *o) {
+  setobj2s(L, L->top.p, o);
+  api_incr_top(L);
+}
+
+
+static void badexit (const char *fmt, const char *s1, const char *s2) {
+  fprintf(stderr, fmt, s1);
+  if (s2)
+    fprintf(stderr, "extra info: %s\n", s2);
+  /* avoid assertion failures when exiting */
+  l_memcontrol.numblocks = l_memcontrol.total = 0;
+  exit(EXIT_FAILURE);
+}
+
+
+static int tpanic (lua_State *L) {
+  const char *msg = lua_tostring(L, -1);
+  if (msg == NULL) msg = "error object is not a string";
+  return (badexit("PANIC: unprotected error in call to Lua API (%s)\n",
+                   msg, NULL),
+          0);  /* do not return to Lua */
+}
+
+
+/*
+** Warning function for tests. First, it concatenates all parts of
+** a warning in buffer 'buff'. Then, it has three modes:
+** - 0.normal: messages starting with '#' are shown on standard output;
+** - other messages abort the tests (they represent real warning
+** conditions; the standard tests should not generate these conditions
+** unexpectedly);
+** - 1.allow: all messages are shown;
+** - 2.store: all warnings go to the global '_WARN';
+*/
+static void warnf (void *ud, const char *msg, int tocont) {
+  lua_State *L = cast(lua_State *, ud);
+  static char buff[200] = "";  /* should be enough for tests... */
+  static int onoff = 0;
+  static int mode = 0;  /* start in normal mode */
+  static int lasttocont = 0;
+  if (!lasttocont && !tocont && *msg == '@') {  /* control message? */
+    if (buff[0] != '\0')
+      badexit("Control warning during warning: %s\naborting...\n", msg, buff);
+    if (strcmp(msg, "@off") == 0)
+      onoff = 0;
+    else if (strcmp(msg, "@on") == 0)
+      onoff = 1;
+    else if (strcmp(msg, "@normal") == 0)
+      mode = 0;
+    else if (strcmp(msg, "@allow") == 0)
+      mode = 1;
+    else if (strcmp(msg, "@store") == 0)
+      mode = 2;
+    else
+      badexit("Invalid control warning in test mode: %s\naborting...\n",
+              msg, NULL);
+    return;
+  }
+  lasttocont = tocont;
+  if (strlen(msg) >= sizeof(buff) - strlen(buff))
+    badexit("warnf-buffer overflow (%s)\n", msg, buff);
+  strcat(buff, msg);  /* add new message to current warning */
+  if (!tocont) {  /* message finished? */
+    lua_unlock(L);
+    luaL_checkstack(L, 1, "warn stack space");
+    lua_getglobal(L, "_WARN");
+    if (!lua_toboolean(L, -1))
+      lua_pop(L, 1);  /* ok, no previous unexpected warning */
+    else {
+      badexit("Unhandled warning in store mode: %s\naborting...\n",
+              lua_tostring(L, -1), buff);
+    }
+    lua_lock(L);
+    switch (mode) {
+      case 0: {  /* normal */
+        if (buff[0] != '#' && onoff)  /* unexpected warning? */
+          badexit("Unexpected warning in test mode: %s\naborting...\n",
+                  buff, NULL);
+      }  /* FALLTHROUGH */
+      case 1: {  /* allow */
+        if (onoff)
+          fprintf(stderr, "Lua warning: %s\n", buff);  /* print warning */
+        break;
+      }
+      case 2: {  /* store */
+        lua_unlock(L);
+        luaL_checkstack(L, 1, "warn stack space");
+        lua_pushstring(L, buff);
+        lua_setglobal(L, "_WARN");  /* assign message to global '_WARN' */
+        lua_lock(L);
+        break;
+      }
+    }
+    buff[0] = '\0';  /* prepare buffer for next warning */
+  }
+}
+
+
+/*
+** {======================================================================
+** Controlled version for realloc.
+** =======================================================================
+*/
+
+#define MARK		0x55  /* 01010101 (a nice pattern) */
+
+typedef union Header {
+  LUAI_MAXALIGN;
+  struct {
+    size_t size;
+    int type;
+  } d;
+} Header;
+
+
+#if !defined(EXTERNMEMCHECK)
+
+/* full memory check */
+#define MARKSIZE	16  /* size of marks after each block */
+#define fillmem(mem,size)	memset(mem, -MARK, size)
+
+#else
+
+/* external memory check: don't do it twice */
+#define MARKSIZE	0
+#define fillmem(mem,size)	/* empty */
+
+#endif
+
+
+Memcontrol l_memcontrol =
+  {0, 0UL, 0UL, 0UL, 0UL, (~0UL),
+   {0UL, 0UL, 0UL, 0UL, 0UL, 0UL, 0UL, 0UL, 0UL}};
+
+
+static void freeblock (Memcontrol *mc, Header *block) {
+  if (block) {
+    size_t size = block->d.size;
+    int i;
+    for (i = 0; i < MARKSIZE; i++)  /* check marks after block */
+      lua_assert(*(cast_charp(block + 1) + size + i) == MARK);
+    mc->objcount[block->d.type]--;
+    fillmem(block, sizeof(Header) + size + MARKSIZE);  /* erase block */
+    free(block);  /* actually free block */
+    mc->numblocks--;  /* update counts */
+    mc->total -= size;
+  }
+}
+
+
+void *debug_realloc (void *ud, void *b, size_t oldsize, size_t size) {
+  Memcontrol *mc = cast(Memcontrol *, ud);
+  Header *block = cast(Header *, b);
+  int type;
+  if (mc->memlimit == 0) {  /* first time? */
+    char *limit = getenv("MEMLIMIT");  /* initialize memory limit */
+    mc->memlimit = limit ? strtoul(limit, NULL, 10) : ULONG_MAX;
+  }
+  if (block == NULL) {
+    type = (oldsize < LUA_NUMTAGS) ? oldsize : 0;
+    oldsize = 0;
+  }
+  else {
+    block--;  /* go to real header */
+    type = block->d.type;
+    lua_assert(oldsize == block->d.size);
+  }
+  if (size == 0) {
+    freeblock(mc, block);
+    return NULL;
+  }
+  if (mc->failnext) {
+    mc->failnext = 0;
+    return NULL;  /* fake a single memory allocation error */
+  }
+  if (mc->countlimit != ~0UL && size != oldsize) {  /* count limit in use? */
+    if (mc->countlimit == 0)
+      return NULL;  /* fake a memory allocation error */
+    mc->countlimit--;
+  }
+  if (size > oldsize && mc->total+size-oldsize > mc->memlimit)
+    return NULL;  /* fake a memory allocation error */
+  else {
+    Header *newblock;
+    int i;
+    size_t commonsize = (oldsize < size) ? oldsize : size;
+    size_t realsize = sizeof(Header) + size + MARKSIZE;
+    if (realsize < size) return NULL;  /* arithmetic overflow! */
+    newblock = cast(Header *, malloc(realsize));  /* alloc a new block */
+    if (newblock == NULL)
+      return NULL;  /* really out of memory? */
+    if (block) {
+      memcpy(newblock + 1, block + 1, commonsize);  /* copy old contents */
+      freeblock(mc, block);  /* erase (and check) old copy */
+    }
+    /* initialize new part of the block with something weird */
+    fillmem(cast_charp(newblock + 1) + commonsize, size - commonsize);
+    /* initialize marks after block */
+    for (i = 0; i < MARKSIZE; i++)
+      *(cast_charp(newblock + 1) + size + i) = MARK;
+    newblock->d.size = size;
+    newblock->d.type = type;
+    mc->total += size;
+    if (mc->total > mc->maxmem)
+      mc->maxmem = mc->total;
+    mc->numblocks++;
+    mc->objcount[type]++;
+    return newblock + 1;
+  }
+}
+
+
+/* }====================================================================== */
+
+
+
+/*
+** {=====================================================================
+** Functions to check memory consistency.
+** Most of these checks are done through asserts, so this code does
+** not make sense with asserts off. For this reason, it uses 'assert'
+** directly, instead of 'lua_assert'.
+** ======================================================================
+*/
+
+#include <assert.h>
+
+/*
+** Check GC invariants. For incremental mode, a black object cannot
+** point to a white one. For generational mode, really old objects
+** cannot point to young objects. Both old1 and touched2 objects
+** cannot point to new objects (but can point to survivals).
+** (Threads and open upvalues, despite being marked "really old",
+** continue to be visited in all collections, and therefore can point to
+** new objects. They, and only they, are old but gray.)
+*/
+static int testobjref1 (global_State *g, GCObject *f, GCObject *t) {
+  if (isdead(g,t)) return 0;
+  if (issweepphase(g))
+    return 1;  /* no invariants */
+  else if (g->gckind == KGC_INC)
+    return !(isblack(f) && iswhite(t));  /* basic incremental invariant */
+  else {  /* generational mode */
+    if ((getage(f) == G_OLD && isblack(f)) && !isold(t))
+      return 0;
+    if (((getage(f) == G_OLD1 || getage(f) == G_TOUCHED2) && isblack(f)) &&
+          getage(t) == G_NEW)
+      return 0;
+    return 1;
+  }
+}
+
+
+static void printobj (global_State *g, GCObject *o) {
+  printf("||%s(%p)-%c%c(%02X)||",
+           ttypename(novariant(o->tt)), (void *)o,
+           isdead(g,o) ? 'd' : isblack(o) ? 'b' : iswhite(o) ? 'w' : 'g',
+           "ns01oTt"[getage(o)], o->marked);
+  if (o->tt == LUA_VSHRSTR || o->tt == LUA_VLNGSTR)
+    printf(" '%s'", getstr(gco2ts(o)));
+}
+
+
+void lua_printobj (lua_State *L, struct GCObject *o) {
+  printobj(G(L), o);
+}
+
+static int testobjref (global_State *g, GCObject *f, GCObject *t) {
+  int r1 = testobjref1(g, f, t);
+  if (!r1) {
+    printf("%d(%02X) - ", g->gcstate, g->currentwhite);
+    printobj(g, f);
+    printf("  ->  ");
+    printobj(g, t);
+    printf("\n");
+  }
+  return r1;
+}
+
+
+static void checkobjref (global_State *g, GCObject *f, GCObject *t) {
+    assert(testobjref(g, f, t));
+}
+
+
+/*
+** Version where 't' can be NULL. In that case, it should not apply the
+** macro 'obj2gco' over the object. ('t' may have several types, so this
+** definition must be a macro.)  Most checks need this version, because
+** the check may run while an object is still being created.
+*/
+#define checkobjrefN(g,f,t)	{ if (t) checkobjref(g,f,obj2gco(t)); }
+
+
+static void checkvalref (global_State *g, GCObject *f, const TValue *t) {
+  assert(!iscollectable(t) || (righttt(t) && testobjref(g, f, gcvalue(t))));
+}
+
+
+static void checktable (global_State *g, Table *h) {
+  unsigned int i;
+  unsigned int asize = luaH_realasize(h);
+  Node *n, *limit = gnode(h, sizenode(h));
+  GCObject *hgc = obj2gco(h);
+  checkobjrefN(g, hgc, h->metatable);
+  for (i = 0; i < asize; i++)
+    checkvalref(g, hgc, &h->array[i]);
+  for (n = gnode(h, 0); n < limit; n++) {
+    if (!isempty(gval(n))) {
+      TValue k;
+      getnodekey(g->mainthread, &k, n);
+      assert(!keyisnil(n));
+      checkvalref(g, hgc, &k);
+      checkvalref(g, hgc, gval(n));
+    }
+  }
+}
+
+
+static void checkudata (global_State *g, Udata *u) {
+  int i;
+  GCObject *hgc = obj2gco(u);
+  checkobjrefN(g, hgc, u->metatable);
+  for (i = 0; i < u->nuvalue; i++)
+    checkvalref(g, hgc, &u->uv[i].uv);
+}
+
+
+static void checkproto (global_State *g, Proto *f) {
+  int i;
+  GCObject *fgc = obj2gco(f);
+  checkobjrefN(g, fgc, f->source);
+  for (i=0; i<f->sizek; i++) {
+    if (iscollectable(f->k + i))
+      checkobjref(g, fgc, gcvalue(f->k + i));
+  }
+  for (i=0; i<f->sizeupvalues; i++)
+    checkobjrefN(g, fgc, f->upvalues[i].name);
+  for (i=0; i<f->sizep; i++)
+    checkobjrefN(g, fgc, f->p[i]);
+  for (i=0; i<f->sizelocvars; i++)
+    checkobjrefN(g, fgc, f->locvars[i].varname);
+}
+
+
+static void checkCclosure (global_State *g, CClosure *cl) {
+  GCObject *clgc = obj2gco(cl);
+  int i;
+  for (i = 0; i < cl->nupvalues; i++)
+    checkvalref(g, clgc, &cl->upvalue[i]);
+}
+
+
+static void checkLclosure (global_State *g, LClosure *cl) {
+  GCObject *clgc = obj2gco(cl);
+  int i;
+  checkobjrefN(g, clgc, cl->p);
+  for (i=0; i<cl->nupvalues; i++) {
+    UpVal *uv = cl->upvals[i];
+    if (uv) {
+      checkobjrefN(g, clgc, uv);
+      if (!upisopen(uv))
+        checkvalref(g, obj2gco(uv), uv->v.p);
+    }
+  }
+}
+
+
+static int lua_checkpc (CallInfo *ci) {
+  if (!isLua(ci)) return 1;
+  else {
+    StkId f = ci->func.p;
+    Proto *p = clLvalue(s2v(f))->p;
+    return p->code <= ci->u.l.savedpc &&
+           ci->u.l.savedpc <= p->code + p->sizecode;
+  }
+}
+
+
+static void checkstack (global_State *g, lua_State *L1) {
+  StkId o;
+  CallInfo *ci;
+  UpVal *uv;
+  assert(!isdead(g, L1));
+  if (L1->stack.p == NULL) {  /* incomplete thread? */
+    assert(L1->openupval == NULL && L1->ci == NULL);
+    return;
+  }
+  for (uv = L1->openupval; uv != NULL; uv = uv->u.open.next)
+    assert(upisopen(uv));  /* must be open */
+  assert(L1->top.p <= L1->stack_last.p);
+  assert(L1->tbclist.p <= L1->top.p);
+  for (ci = L1->ci; ci != NULL; ci = ci->previous) {
+    assert(ci->top.p <= L1->stack_last.p);
+    assert(lua_checkpc(ci));
+  }
+  for (o = L1->stack.p; o < L1->stack_last.p; o++)
+    checkliveness(L1, s2v(o));  /* entire stack must have valid values */
+}
+
+
+static void checkrefs (global_State *g, GCObject *o) {
+  switch (o->tt) {
+    case LUA_VUSERDATA: {
+      checkudata(g, gco2u(o));
+      break;
+    }
+    case LUA_VUPVAL: {
+      checkvalref(g, o, gco2upv(o)->v.p);
+      break;
+    }
+    case LUA_VTABLE: {
+      checktable(g, gco2t(o));
+      break;
+    }
+    case LUA_VTHREAD: {
+      checkstack(g, gco2th(o));
+      break;
+    }
+    case LUA_VLCL: {
+      checkLclosure(g, gco2lcl(o));
+      break;
+    }
+    case LUA_VCCL: {
+      checkCclosure(g, gco2ccl(o));
+      break;
+    }
+    case LUA_VPROTO: {
+      checkproto(g, gco2p(o));
+      break;
+    }
+    case LUA_VSHRSTR:
+    case LUA_VLNGSTR: {
+      assert(!isgray(o));  /* strings are never gray */
+      break;
+    }
+    default: assert(0);
+  }
+}
+
+
+/*
+** Check consistency of an object:
+** - Dead objects can only happen in the 'allgc' list during a sweep
+** phase (controlled by the caller through 'maybedead').
+** - During pause, all objects must be white.
+** - In generational mode:
+**   * objects must be old enough for their lists ('listage').
+**   * old objects cannot be white.
+**   * old objects must be black, except for 'touched1', 'old0',
+** threads, and open upvalues.
+*/
+static void checkobject (global_State *g, GCObject *o, int maybedead,
+                         int listage) {
+  if (isdead(g, o))
+    assert(maybedead);
+  else {
+    assert(g->gcstate != GCSpause || iswhite(o));
+    if (g->gckind == KGC_GEN) {  /* generational mode? */
+      assert(getage(o) >= listage);
+      assert(!iswhite(o) || !isold(o));
+      if (isold(o)) {
+        assert(isblack(o) ||
+        getage(o) == G_TOUCHED1 ||
+        getage(o) == G_OLD0 ||
+        o->tt == LUA_VTHREAD ||
+        (o->tt == LUA_VUPVAL && upisopen(gco2upv(o))));
+      }
+    }
+    checkrefs(g, o);
+  }
+}
+
+
+static lu_mem checkgraylist (global_State *g, GCObject *o) {
+  int total = 0;  /* count number of elements in the list */
+  cast_void(g);  /* better to keep it if we need to print an object */
+  while (o) {
+    assert(!!isgray(o) ^ (getage(o) == G_TOUCHED2));
+    assert(!testbit(o->marked, TESTBIT));
+    if (keepinvariant(g))
+      l_setbit(o->marked, TESTBIT);  /* mark that object is in a gray list */
+    total++;
+    switch (o->tt) {
+      case LUA_VTABLE: o = gco2t(o)->gclist; break;
+      case LUA_VLCL: o = gco2lcl(o)->gclist; break;
+      case LUA_VCCL: o = gco2ccl(o)->gclist; break;
+      case LUA_VTHREAD: o = gco2th(o)->gclist; break;
+      case LUA_VPROTO: o = gco2p(o)->gclist; break;
+      case LUA_VUSERDATA:
+        assert(gco2u(o)->nuvalue > 0);
+        o = gco2u(o)->gclist;
+        break;
+      default: assert(0);  /* other objects cannot be in a gray list */
+    }
+  }
+  return total;
+}
+
+
+/*
+** Check objects in gray lists.
+*/
+static lu_mem checkgrays (global_State *g) {
+  int total = 0;  /* count number of elements in all lists */
+  if (!keepinvariant(g)) return total;
+  total += checkgraylist(g, g->gray);
+  total += checkgraylist(g, g->grayagain);
+  total += checkgraylist(g, g->weak);
+  total += checkgraylist(g, g->allweak);
+  total += checkgraylist(g, g->ephemeron);
+  return total;
+}
+
+
+/*
+** Check whether 'o' should be in a gray list. If so, increment
+** 'count' and check its TESTBIT. (It must have been previously set by
+** 'checkgraylist'.)
+*/
+static void incifingray (global_State *g, GCObject *o, lu_mem *count) {
+  if (!keepinvariant(g))
+    return;  /* gray lists not being kept in these phases */
+  if (o->tt == LUA_VUPVAL) {
+    /* only open upvalues can be gray */
+    assert(!isgray(o) || upisopen(gco2upv(o)));
+    return;  /* upvalues are never in gray lists */
+  }
+  /* these are the ones that must be in gray lists */
+  if (isgray(o) || getage(o) == G_TOUCHED2) {
+    (*count)++;
+    assert(testbit(o->marked, TESTBIT));
+    resetbit(o->marked, TESTBIT);  /* prepare for next cycle */
+  }
+}
+
+
+static lu_mem checklist (global_State *g, int maybedead, int tof,
+  GCObject *newl, GCObject *survival, GCObject *old, GCObject *reallyold) {
+  GCObject *o;
+  lu_mem total = 0;  /* number of object that should be in  gray lists */
+  for (o = newl; o != survival; o = o->next) {
+    checkobject(g, o, maybedead, G_NEW);
+    incifingray(g, o, &total);
+    assert(!tof == !tofinalize(o));
+  }
+  for (o = survival; o != old; o = o->next) {
+    checkobject(g, o, 0, G_SURVIVAL);
+    incifingray(g, o, &total);
+    assert(!tof == !tofinalize(o));
+  }
+  for (o = old; o != reallyold; o = o->next) {
+    checkobject(g, o, 0, G_OLD1);
+    incifingray(g, o, &total);
+    assert(!tof == !tofinalize(o));
+  }
+  for (o = reallyold; o != NULL; o = o->next) {
+    checkobject(g, o, 0, G_OLD);
+    incifingray(g, o, &total);
+    assert(!tof == !tofinalize(o));
+  }
+  return total;
+}
+
+
+int lua_checkmemory (lua_State *L) {
+  global_State *g = G(L);
+  GCObject *o;
+  int maybedead;
+  lu_mem totalin;  /* total of objects that are in gray lists */
+  lu_mem totalshould;  /* total of objects that should be in gray lists */
+  if (keepinvariant(g)) {
+    assert(!iswhite(g->mainthread));
+    assert(!iswhite(gcvalue(&g->l_registry)));
+  }
+  assert(!isdead(g, gcvalue(&g->l_registry)));
+  assert(g->sweepgc == NULL || issweepphase(g));
+  totalin = checkgrays(g);
+
+  /* check 'fixedgc' list */
+  for (o = g->fixedgc; o != NULL; o = o->next) {
+    assert(o->tt == LUA_VSHRSTR && isgray(o) && getage(o) == G_OLD);
+  }
+
+  /* check 'allgc' list */
+  maybedead = (GCSatomic < g->gcstate && g->gcstate <= GCSswpallgc);
+  totalshould = checklist(g, maybedead, 0, g->allgc,
+                             g->survival, g->old1, g->reallyold);
+
+  /* check 'finobj' list */
+  totalshould += checklist(g, 0, 1, g->finobj,
+                              g->finobjsur, g->finobjold1, g->finobjrold);
+
+  /* check 'tobefnz' list */
+  for (o = g->tobefnz; o != NULL; o = o->next) {
+    checkobject(g, o, 0, G_NEW);
+    incifingray(g, o, &totalshould);
+    assert(tofinalize(o));
+    assert(o->tt == LUA_VUSERDATA || o->tt == LUA_VTABLE);
+  }
+  if (keepinvariant(g))
+    assert(totalin == totalshould);
+  return 0;
+}
+
+/* }====================================================== */
+
+
+
+/*
+** {======================================================
+** Disassembler
+** =======================================================
+*/
+
+
+static char *buildop (Proto *p, int pc, char *buff) {
+  char *obuff = buff;
+  Instruction i = p->code[pc];
+  OpCode o = GET_OPCODE(i);
+  const char *name = opnames[o];
+  int line = luaG_getfuncline(p, pc);
+  int lineinfo = (p->lineinfo != NULL) ? p->lineinfo[pc] : 0;
+  if (lineinfo == ABSLINEINFO)
+    buff += sprintf(buff, "(__");
+  else
+    buff += sprintf(buff, "(%2d", lineinfo);
+  buff += sprintf(buff, " - %4d) %4d - ", line, pc);
+  switch (getOpMode(o)) {
+    case iABC:
+      sprintf(buff, "%-12s%4d %4d %4d%s", name,
+              GETARG_A(i), GETARG_B(i), GETARG_C(i),
+              GETARG_k(i) ? " (k)" : "");
+      break;
+    case iABx:
+      sprintf(buff, "%-12s%4d %4d", name, GETARG_A(i), GETARG_Bx(i));
+      break;
+    case iAsBx:
+      sprintf(buff, "%-12s%4d %4d", name, GETARG_A(i), GETARG_sBx(i));
+      break;
+    case iAx:
+      sprintf(buff, "%-12s%4d", name, GETARG_Ax(i));
+      break;
+    case isJ:
+      sprintf(buff, "%-12s%4d", name, GETARG_sJ(i));
+      break;
+  }
+  return obuff;
+}
+
+
+#if 0
+void luaI_printcode (Proto *pt, int size) {
+  int pc;
+  for (pc=0; pc<size; pc++) {
+    char buff[100];
+    printf("%s\n", buildop(pt, pc, buff));
+  }
+  printf("-------\n");
+}
+
+
+void luaI_printinst (Proto *pt, int pc) {
+  char buff[100];
+  printf("%s\n", buildop(pt, pc, buff));
+}
+#endif
+
+
+static int listcode (lua_State *L) {
+  int pc;
+  Proto *p;
+  luaL_argcheck(L, lua_isfunction(L, 1) && !lua_iscfunction(L, 1),
+                 1, "Lua function expected");
+  p = getproto(obj_at(L, 1));
+  lua_newtable(L);
+  setnameval(L, "maxstack", p->maxstacksize);
+  setnameval(L, "numparams", p->numparams);
+  for (pc=0; pc<p->sizecode; pc++) {
+    char buff[100];
+    lua_pushinteger(L, pc+1);
+    lua_pushstring(L, buildop(p, pc, buff));
+    lua_settable(L, -3);
+  }
+  return 1;
+}
+
+
+static int printcode (lua_State *L) {
+  int pc;
+  Proto *p;
+  luaL_argcheck(L, lua_isfunction(L, 1) && !lua_iscfunction(L, 1),
+                 1, "Lua function expected");
+  p = getproto(obj_at(L, 1));
+  printf("maxstack: %d\n", p->maxstacksize);
+  printf("numparams: %d\n", p->numparams);
+  for (pc=0; pc<p->sizecode; pc++) {
+    char buff[100];
+    printf("%s\n", buildop(p, pc, buff));
+  }
+  return 0;
+}
+
+
+static int listk (lua_State *L) {
+  Proto *p;
+  int i;
+  luaL_argcheck(L, lua_isfunction(L, 1) && !lua_iscfunction(L, 1),
+                 1, "Lua function expected");
+  p = getproto(obj_at(L, 1));
+  lua_createtable(L, p->sizek, 0);
+  for (i=0; i<p->sizek; i++) {
+    pushobject(L, p->k+i);
+    lua_rawseti(L, -2, i+1);
+  }
+  return 1;
+}
+
+
+static int listabslineinfo (lua_State *L) {
+  Proto *p;
+  int i;
+  luaL_argcheck(L, lua_isfunction(L, 1) && !lua_iscfunction(L, 1),
+                 1, "Lua function expected");
+  p = getproto(obj_at(L, 1));
+  luaL_argcheck(L, p->abslineinfo != NULL, 1, "function has no debug info");
+  lua_createtable(L, 2 * p->sizeabslineinfo, 0);
+  for (i=0; i < p->sizeabslineinfo; i++) {
+    lua_pushinteger(L, p->abslineinfo[i].pc);
+    lua_rawseti(L, -2, 2 * i + 1);
+    lua_pushinteger(L, p->abslineinfo[i].line);
+    lua_rawseti(L, -2, 2 * i + 2);
+  }
+  return 1;
+}
+
+
+static int listlocals (lua_State *L) {
+  Proto *p;
+  int pc = cast_int(luaL_checkinteger(L, 2)) - 1;
+  int i = 0;
+  const char *name;
+  luaL_argcheck(L, lua_isfunction(L, 1) && !lua_iscfunction(L, 1),
+                 1, "Lua function expected");
+  p = getproto(obj_at(L, 1));
+  while ((name = luaF_getlocalname(p, ++i, pc)) != NULL)
+    lua_pushstring(L, name);
+  return i-1;
+}
+
+/* }====================================================== */
+
+
+
+static void printstack (lua_State *L) {
+  int i;
+  int n = lua_gettop(L);
+  printf("stack: >>\n");
+  for (i = 1; i <= n; i++) {
+    printf("%3d: %s\n", i, luaL_tolstring(L, i, NULL));
+    lua_pop(L, 1);
+  }
+  printf("<<\n");
+}
+
+
+static int get_limits (lua_State *L) {
+  lua_createtable(L, 0, 6);
+  setnameval(L, "IS32INT", LUAI_IS32INT);
+  setnameval(L, "MAXARG_Ax", MAXARG_Ax);
+  setnameval(L, "MAXARG_Bx", MAXARG_Bx);
+  setnameval(L, "OFFSET_sBx", OFFSET_sBx);
+  setnameval(L, "LFPF", LFIELDS_PER_FLUSH);
+  setnameval(L, "NUM_OPCODES", NUM_OPCODES);
+  return 1;
+}
+
+
+static int mem_query (lua_State *L) {
+  if (lua_isnone(L, 1)) {
+    lua_pushinteger(L, l_memcontrol.total);
+    lua_pushinteger(L, l_memcontrol.numblocks);
+    lua_pushinteger(L, l_memcontrol.maxmem);
+    return 3;
+  }
+  else if (lua_isnumber(L, 1)) {
+    unsigned long limit = cast(unsigned long, luaL_checkinteger(L, 1));
+    if (limit == 0) limit = ULONG_MAX;
+    l_memcontrol.memlimit = limit;
+    return 0;
+  }
+  else {
+    const char *t = luaL_checkstring(L, 1);
+    int i;
+    for (i = LUA_NUMTAGS - 1; i >= 0; i--) {
+      if (strcmp(t, ttypename(i)) == 0) {
+        lua_pushinteger(L, l_memcontrol.objcount[i]);
+        return 1;
+      }
+    }
+    return luaL_error(L, "unknown type '%s'", t);
+  }
+}
+
+
+static int alloc_count (lua_State *L) {
+  if (lua_isnone(L, 1))
+    l_memcontrol.countlimit = ~0L;
+  else
+    l_memcontrol.countlimit = luaL_checkinteger(L, 1);
+  return 0;
+}
+
+
+static int alloc_failnext (lua_State *L) {
+  UNUSED(L);
+  l_memcontrol.failnext = 1;
+  return 0;
+}
+
+
+static int settrick (lua_State *L) {
+  if (ttisnil(obj_at(L, 1)))
+    l_Trick = NULL;
+  else
+    l_Trick = gcvalue(obj_at(L, 1));
+  return 0;
+}
+
+
+static int gc_color (lua_State *L) {
+  TValue *o;
+  luaL_checkany(L, 1);
+  o = obj_at(L, 1);
+  if (!iscollectable(o))
+    lua_pushstring(L, "no collectable");
+  else {
+    GCObject *obj = gcvalue(o);
+    lua_pushstring(L, isdead(G(L), obj) ? "dead" :
+                      iswhite(obj) ? "white" :
+                      isblack(obj) ? "black" : "gray");
+  }
+  return 1;
+}
+
+
+static int gc_age (lua_State *L) {
+  TValue *o;
+  luaL_checkany(L, 1);
+  o = obj_at(L, 1);
+  if (!iscollectable(o))
+    lua_pushstring(L, "no collectable");
+  else {
+    static const char *gennames[] = {"new", "survival", "old0", "old1",
+                                     "old", "touched1", "touched2"};
+    GCObject *obj = gcvalue(o);
+    lua_pushstring(L, gennames[getage(obj)]);
+  }
+  return 1;
+}
+
+
+static int gc_printobj (lua_State *L) {
+  TValue *o;
+  luaL_checkany(L, 1);
+  o = obj_at(L, 1);
+  if (!iscollectable(o))
+    printf("no collectable\n");
+  else {
+    GCObject *obj = gcvalue(o);
+    printobj(G(L), obj);
+    printf("\n");
+  }
+  return 0;
+}
+
+
+static int gc_state (lua_State *L) {
+  static const char *statenames[] = {
+    "propagate", "atomic", "enteratomic", "sweepallgc", "sweepfinobj",
+    "sweeptobefnz", "sweepend", "callfin", "pause", ""};
+  static const int states[] = {
+    GCSpropagate, GCSenteratomic, GCSatomic, GCSswpallgc, GCSswpfinobj,
+    GCSswptobefnz, GCSswpend, GCScallfin, GCSpause, -1};
+  int option = states[luaL_checkoption(L, 1, "", statenames)];
+  if (option == -1) {
+    lua_pushstring(L, statenames[G(L)->gcstate]);
+    return 1;
+  }
+  else {
+    global_State *g = G(L);
+    if (G(L)->gckind == KGC_GEN)
+      luaL_error(L, "cannot change states in generational mode");
+    lua_lock(L);
+    if (option < g->gcstate) {  /* must cross 'pause'? */
+      luaC_runtilstate(L, bitmask(GCSpause));  /* run until pause */
+    }
+    luaC_runtilstate(L, bitmask(option));
+    lua_assert(G(L)->gcstate == option);
+    lua_unlock(L);
+    return 0;
+  }
+}
+
+
+static int hash_query (lua_State *L) {
+  if (lua_isnone(L, 2)) {
+    luaL_argcheck(L, lua_type(L, 1) == LUA_TSTRING, 1, "string expected");
+    lua_pushinteger(L, tsvalue(obj_at(L, 1))->hash);
+  }
+  else {
+    TValue *o = obj_at(L, 1);
+    Table *t;
+    luaL_checktype(L, 2, LUA_TTABLE);
+    t = hvalue(obj_at(L, 2));
+    lua_pushinteger(L, luaH_mainposition(t, o) - t->node);
+  }
+  return 1;
+}
+
+
+static int stacklevel (lua_State *L) {
+  unsigned long a = 0;
+  lua_pushinteger(L, (L->top.p - L->stack.p));
+  lua_pushinteger(L, stacksize(L));
+  lua_pushinteger(L, L->nCcalls);
+  lua_pushinteger(L, L->nci);
+  lua_pushinteger(L, (unsigned long)&a);
+  return 5;
+}
+
+
+static int table_query (lua_State *L) {
+  const Table *t;
+  int i = cast_int(luaL_optinteger(L, 2, -1));
+  unsigned int asize;
+  luaL_checktype(L, 1, LUA_TTABLE);
+  t = hvalue(obj_at(L, 1));
+  asize = luaH_realasize(t);
+  if (i == -1) {
+    lua_pushinteger(L, asize);
+    lua_pushinteger(L, allocsizenode(t));
+    lua_pushinteger(L, isdummy(t) ? 0 : t->lastfree - t->node);
+    lua_pushinteger(L, t->alimit);
+    return 4;
+  }
+  else if ((unsigned int)i < asize) {
+    lua_pushinteger(L, i);
+    pushobject(L, &t->array[i]);
+    lua_pushnil(L);
+  }
+  else if ((i -= asize) < sizenode(t)) {
+    TValue k;
+    getnodekey(L, &k, gnode(t, i));
+    if (!isempty(gval(gnode(t, i))) ||
+        ttisnil(&k) ||
+        ttisnumber(&k)) {
+      pushobject(L, &k);
+    }
+    else
+      lua_pushliteral(L, "<undef>");
+    pushobject(L, gval(gnode(t, i)));
+    if (gnext(&t->node[i]) != 0)
+      lua_pushinteger(L, gnext(&t->node[i]));
+    else
+      lua_pushnil(L);
+  }
+  return 3;
+}
+
+
+static int string_query (lua_State *L) {
+  stringtable *tb = &G(L)->strt;
+  int s = cast_int(luaL_optinteger(L, 1, 0)) - 1;
+  if (s == -1) {
+    lua_pushinteger(L ,tb->size);
+    lua_pushinteger(L ,tb->nuse);
+    return 2;
+  }
+  else if (s < tb->size) {
+    TString *ts;
+    int n = 0;
+    for (ts = tb->hash[s]; ts != NULL; ts = ts->u.hnext) {
+      setsvalue2s(L, L->top.p, ts);
+      api_incr_top(L);
+      n++;
+    }
+    return n;
+  }
+  else return 0;
+}
+
+
+static int tref (lua_State *L) {
+  int level = lua_gettop(L);
+  luaL_checkany(L, 1);
+  lua_pushvalue(L, 1);
+  lua_pushinteger(L, luaL_ref(L, LUA_REGISTRYINDEX));
+  cast_void(level);  /* to avoid warnings */
+  lua_assert(lua_gettop(L) == level+1);  /* +1 for result */
+  return 1;
+}
+
+static int getref (lua_State *L) {
+  int level = lua_gettop(L);
+  lua_rawgeti(L, LUA_REGISTRYINDEX, luaL_checkinteger(L, 1));
+  cast_void(level);  /* to avoid warnings */
+  lua_assert(lua_gettop(L) == level+1);
+  return 1;
+}
+
+static int unref (lua_State *L) {
+  int level = lua_gettop(L);
+  luaL_unref(L, LUA_REGISTRYINDEX, cast_int(luaL_checkinteger(L, 1)));
+  cast_void(level);  /* to avoid warnings */
+  lua_assert(lua_gettop(L) == level);
+  return 0;
+}
+
+
+static int upvalue (lua_State *L) {
+  int n = cast_int(luaL_checkinteger(L, 2));
+  luaL_checktype(L, 1, LUA_TFUNCTION);
+  if (lua_isnone(L, 3)) {
+    const char *name = lua_getupvalue(L, 1, n);
+    if (name == NULL) return 0;
+    lua_pushstring(L, name);
+    return 2;
+  }
+  else {
+    const char *name = lua_setupvalue(L, 1, n);
+    lua_pushstring(L, name);
+    return 1;
+  }
+}
+
+
+static int newuserdata (lua_State *L) {
+  size_t size = cast_sizet(luaL_optinteger(L, 1, 0));
+  int nuv = luaL_optinteger(L, 2, 0);
+  char *p = cast_charp(lua_newuserdatauv(L, size, nuv));
+  while (size--) *p++ = '\0';
+  return 1;
+}
+
+
+static int pushuserdata (lua_State *L) {
+  lua_Integer u = luaL_checkinteger(L, 1);
+  lua_pushlightuserdata(L, cast_voidp(cast_sizet(u)));
+  return 1;
+}
+
+
+static int udataval (lua_State *L) {
+  lua_pushinteger(L, cast(long, lua_touserdata(L, 1)));
+  return 1;
+}
+
+
+static int doonnewstack (lua_State *L) {
+  lua_State *L1 = lua_newthread(L);
+  size_t l;
+  const char *s = luaL_checklstring(L, 1, &l);
+  int status = luaL_loadbuffer(L1, s, l, s);
+  if (status == LUA_OK)
+    status = lua_pcall(L1, 0, 0, 0);
+  lua_pushinteger(L, status);
+  return 1;
+}
+
+
+static int s2d (lua_State *L) {
+  lua_pushnumber(L, cast_num(*cast(const double *, luaL_checkstring(L, 1))));
+  return 1;
+}
+
+
+static int d2s (lua_State *L) {
+  double d = cast(double, luaL_checknumber(L, 1));
+  lua_pushlstring(L, cast_charp(&d), sizeof(d));
+  return 1;
+}
+
+
+static int num2int (lua_State *L) {
+  lua_pushinteger(L, lua_tointeger(L, 1));
+  return 1;
+}
+
+
+static int newstate (lua_State *L) {
+  void *ud;
+  lua_Alloc f = lua_getallocf(L, &ud);
+  lua_State *L1 = lua_newstate(f, ud);
+  if (L1) {
+    lua_atpanic(L1, tpanic);
+    lua_pushlightuserdata(L, L1);
+  }
+  else
+    lua_pushnil(L);
+  return 1;
+}
+
+
+static lua_State *getstate (lua_State *L) {
+  lua_State *L1 = cast(lua_State *, lua_touserdata(L, 1));
+  luaL_argcheck(L, L1 != NULL, 1, "state expected");
+  return L1;
+}
+
+
+static int loadlib (lua_State *L) {
+  static const luaL_Reg libs[] = {
+    {LUA_GNAME, luaopen_base},
+    {"coroutine", luaopen_coroutine},
+    {"debug", luaopen_debug},
+    {"io", luaopen_io},
+    {"os", luaopen_os},
+    {"math", luaopen_math},
+    {"string", luaopen_string},
+    {"table", luaopen_table},
+    {"T", luaB_opentests},
+    {NULL, NULL}
+  };
+  lua_State *L1 = getstate(L);
+  int i;
+  luaL_requiref(L1, "package", luaopen_package, 0);
+  lua_assert(lua_type(L1, -1) == LUA_TTABLE);
+  /* 'requiref' should not reload module already loaded... */
+  luaL_requiref(L1, "package", NULL, 1);  /* seg. fault if it reloads */
+  /* ...but should return the same module */
+  lua_assert(lua_compare(L1, -1, -2, LUA_OPEQ));
+  luaL_getsubtable(L1, LUA_REGISTRYINDEX, LUA_PRELOAD_TABLE);
+  for (i = 0; libs[i].name; i++) {
+    lua_pushcfunction(L1, libs[i].func);
+    lua_setfield(L1, -2, libs[i].name);
+  }
+  return 0;
+}
+
+static int closestate (lua_State *L) {
+  lua_State *L1 = getstate(L);
+  lua_close(L1);
+  return 0;
+}
+
+static int doremote (lua_State *L) {
+  lua_State *L1 = getstate(L);
+  size_t lcode;
+  const char *code = luaL_checklstring(L, 2, &lcode);
+  int status;
+  lua_settop(L1, 0);
+  status = luaL_loadbuffer(L1, code, lcode, code);
+  if (status == LUA_OK)
+    status = lua_pcall(L1, 0, LUA_MULTRET, 0);
+  if (status != LUA_OK) {
+    lua_pushnil(L);
+    lua_pushstring(L, lua_tostring(L1, -1));
+    lua_pushinteger(L, status);
+    return 3;
+  }
+  else {
+    int i = 0;
+    while (!lua_isnone(L1, ++i))
+      lua_pushstring(L, lua_tostring(L1, i));
+    lua_pop(L1, i-1);
+    return i-1;
+  }
+}
+
+
+static int log2_aux (lua_State *L) {
+  unsigned int x = (unsigned int)luaL_checkinteger(L, 1);
+  lua_pushinteger(L, luaO_ceillog2(x));
+  return 1;
+}
+
+
+struct Aux { jmp_buf jb; const char *paniccode; lua_State *L; };
+
+/*
+** does a long-jump back to "main program".
+*/
+static int panicback (lua_State *L) {
+  struct Aux *b;
+  lua_checkstack(L, 1);  /* open space for 'Aux' struct */
+  lua_getfield(L, LUA_REGISTRYINDEX, "_jmpbuf");  /* get 'Aux' struct */
+  b = (struct Aux *)lua_touserdata(L, -1);
+  lua_pop(L, 1);  /* remove 'Aux' struct */
+  runC(b->L, L, b->paniccode);  /* run optional panic code */
+  longjmp(b->jb, 1);
+  return 1;  /* to avoid warnings */
+}
+
+static int checkpanic (lua_State *L) {
+  struct Aux b;
+  void *ud;
+  lua_State *L1;
+  const char *code = luaL_checkstring(L, 1);
+  lua_Alloc f = lua_getallocf(L, &ud);
+  b.paniccode = luaL_optstring(L, 2, "");
+  b.L = L;
+  L1 = lua_newstate(f, ud);  /* create new state */
+  if (L1 == NULL) {  /* error? */
+    lua_pushnil(L);
+    return 1;
+  }
+  lua_atpanic(L1, panicback);  /* set its panic function */
+  lua_pushlightuserdata(L1, &b);
+  lua_setfield(L1, LUA_REGISTRYINDEX, "_jmpbuf");  /* store 'Aux' struct */
+  if (setjmp(b.jb) == 0) {  /* set jump buffer */
+    runC(L, L1, code);  /* run code unprotected */
+    lua_pushliteral(L, "no errors");
+  }
+  else {  /* error handling */
+    /* move error message to original state */
+    lua_pushstring(L, lua_tostring(L1, -1));
+  }
+  lua_close(L1);
+  return 1;
+}
+
+
+
+/*
+** {====================================================================
+** function to test the API with C. It interprets a kind of assembler
+** language with calls to the API, so the test can be driven by Lua code
+** =====================================================================
+*/
+
+
+static void sethookaux (lua_State *L, int mask, int count, const char *code);
+
+static const char *const delimits = " \t\n,;";
+
+static void skip (const char **pc) {
+  for (;;) {
+    if (**pc != '\0' && strchr(delimits, **pc)) (*pc)++;
+    else if (**pc == '#') {  /* comment? */
+      while (**pc != '\n' && **pc != '\0') (*pc)++;  /* until end-of-line */
+    }
+    else break;
+  }
+}
+
+static int getnum_aux (lua_State *L, lua_State *L1, const char **pc) {
+  int res = 0;
+  int sig = 1;
+  skip(pc);
+  if (**pc == '.') {
+    res = cast_int(lua_tointeger(L1, -1));
+    lua_pop(L1, 1);
+    (*pc)++;
+    return res;
+  }
+  else if (**pc == '*') {
+    res = lua_gettop(L1);
+    (*pc)++;
+    return res;
+  }
+  else if (**pc == '-') {
+    sig = -1;
+    (*pc)++;
+  }
+  if (!lisdigit(cast_uchar(**pc)))
+    luaL_error(L, "number expected (%s)", *pc);
+  while (lisdigit(cast_uchar(**pc))) res = res*10 + (*(*pc)++) - '0';
+  return sig*res;
+}
+
+static const char *getstring_aux (lua_State *L, char *buff, const char **pc) {
+  int i = 0;
+  skip(pc);
+  if (**pc == '"' || **pc == '\'') {  /* quoted string? */
+    int quote = *(*pc)++;
+    while (**pc != quote) {
+      if (**pc == '\0') luaL_error(L, "unfinished string in C script");
+      buff[i++] = *(*pc)++;
+    }
+    (*pc)++;
+  }
+  else {
+    while (**pc != '\0' && !strchr(delimits, **pc))
+      buff[i++] = *(*pc)++;
+  }
+  buff[i] = '\0';
+  return buff;
+}
+
+
+static int getindex_aux (lua_State *L, lua_State *L1, const char **pc) {
+  skip(pc);
+  switch (*(*pc)++) {
+    case 'R': return LUA_REGISTRYINDEX;
+    case 'G': return luaL_error(L, "deprecated index 'G'");
+    case 'U': return lua_upvalueindex(getnum_aux(L, L1, pc));
+    default: (*pc)--; return getnum_aux(L, L1, pc);
+  }
+}
+
+
+static const char *const statcodes[] = {"OK", "YIELD", "ERRRUN",
+    "ERRSYNTAX", MEMERRMSG, "ERRGCMM", "ERRERR"};
+
+/*
+** Avoid these stat codes from being collected, to avoid possible
+** memory error when pushing them.
+*/
+static void regcodes (lua_State *L) {
+  unsigned int i;
+  for (i = 0; i < sizeof(statcodes) / sizeof(statcodes[0]); i++) {
+    lua_pushboolean(L, 1);
+    lua_setfield(L, LUA_REGISTRYINDEX, statcodes[i]);
+  }
+}
+
+
+#define EQ(s1)	(strcmp(s1, inst) == 0)
+
+#define getnum		(getnum_aux(L, L1, &pc))
+#define getstring	(getstring_aux(L, buff, &pc))
+#define getindex	(getindex_aux(L, L1, &pc))
+
+
+static int testC (lua_State *L);
+static int Cfunck (lua_State *L, int status, lua_KContext ctx);
+
+/*
+** arithmetic operation encoding for 'arith' instruction
+** LUA_OPIDIV  -> \
+** LUA_OPSHL   -> <
+** LUA_OPSHR   -> >
+** LUA_OPUNM   -> _
+** LUA_OPBNOT  -> !
+*/
+static const char ops[] = "+-*%^/\\&|~<>_!";
+
+static int runC (lua_State *L, lua_State *L1, const char *pc) {
+  char buff[300];
+  int status = 0;
+  if (pc == NULL) return luaL_error(L, "attempt to runC null script");
+  for (;;) {
+    const char *inst = getstring;
+    if EQ("") return 0;
+    else if EQ("absindex") {
+      lua_pushnumber(L1, lua_absindex(L1, getindex));
+    }
+    else if EQ("append") {
+      int t = getindex;
+      int i = lua_rawlen(L1, t);
+      lua_rawseti(L1, t, i + 1);
+    }
+    else if EQ("arith") {
+      int op;
+      skip(&pc);
+      op = strchr(ops, *pc++) - ops;
+      lua_arith(L1, op);
+    }
+    else if EQ("call") {
+      int narg = getnum;
+      int nres = getnum;
+      lua_call(L1, narg, nres);
+    }
+    else if EQ("callk") {
+      int narg = getnum;
+      int nres = getnum;
+      int i = getindex;
+      lua_callk(L1, narg, nres, i, Cfunck);
+    }
+    else if EQ("checkstack") {
+      int sz = getnum;
+      const char *msg = getstring;
+      if (*msg == '\0')
+        msg = NULL;  /* to test 'luaL_checkstack' with no message */
+      luaL_checkstack(L1, sz, msg);
+    }
+    else if EQ("rawcheckstack") {
+      int sz = getnum;
+      lua_pushboolean(L1, lua_checkstack(L1, sz));
+    }
+    else if EQ("compare") {
+      const char *opt = getstring;  /* EQ, LT, or LE */
+      int op = (opt[0] == 'E') ? LUA_OPEQ
+                               : (opt[1] == 'T') ? LUA_OPLT : LUA_OPLE;
+      int a = getindex;
+      int b = getindex;
+      lua_pushboolean(L1, lua_compare(L1, a, b, op));
+    }
+    else if EQ("concat") {
+      lua_concat(L1, getnum);
+    }
+    else if EQ("copy") {
+      int f = getindex;
+      lua_copy(L1, f, getindex);
+    }
+    else if EQ("func2num") {
+      lua_CFunction func = lua_tocfunction(L1, getindex);
+      lua_pushnumber(L1, cast_sizet(func));
+    }
+    else if EQ("getfield") {
+      int t = getindex;
+      lua_getfield(L1, t, getstring);
+    }
+    else if EQ("getglobal") {
+      lua_getglobal(L1, getstring);
+    }
+    else if EQ("getmetatable") {
+      if (lua_getmetatable(L1, getindex) == 0)
+        lua_pushnil(L1);
+    }
+    else if EQ("gettable") {
+      lua_gettable(L1, getindex);
+    }
+    else if EQ("gettop") {
+      lua_pushinteger(L1, lua_gettop(L1));
+    }
+    else if EQ("gsub") {
+      int a = getnum; int b = getnum; int c = getnum;
+      luaL_gsub(L1, lua_tostring(L1, a),
+                    lua_tostring(L1, b),
+                    lua_tostring(L1, c));
+    }
+    else if EQ("insert") {
+      lua_insert(L1, getnum);
+    }
+    else if EQ("iscfunction") {
+      lua_pushboolean(L1, lua_iscfunction(L1, getindex));
+    }
+    else if EQ("isfunction") {
+      lua_pushboolean(L1, lua_isfunction(L1, getindex));
+    }
+    else if EQ("isnil") {
+      lua_pushboolean(L1, lua_isnil(L1, getindex));
+    }
+    else if EQ("isnull") {
+      lua_pushboolean(L1, lua_isnone(L1, getindex));
+    }
+    else if EQ("isnumber") {
+      lua_pushboolean(L1, lua_isnumber(L1, getindex));
+    }
+    else if EQ("isstring") {
+      lua_pushboolean(L1, lua_isstring(L1, getindex));
+    }
+    else if EQ("istable") {
+      lua_pushboolean(L1, lua_istable(L1, getindex));
+    }
+    else if EQ("isudataval") {
+      lua_pushboolean(L1, lua_islightuserdata(L1, getindex));
+    }
+    else if EQ("isuserdata") {
+      lua_pushboolean(L1, lua_isuserdata(L1, getindex));
+    }
+    else if EQ("len") {
+      lua_len(L1, getindex);
+    }
+    else if EQ("Llen") {
+      lua_pushinteger(L1, luaL_len(L1, getindex));
+    }
+    else if EQ("loadfile") {
+      luaL_loadfile(L1, luaL_checkstring(L1, getnum));
+    }
+    else if EQ("loadstring") {
+      const char *s = luaL_checkstring(L1, getnum);
+      luaL_loadstring(L1, s);
+    }
+    else if EQ("newmetatable") {
+      lua_pushboolean(L1, luaL_newmetatable(L1, getstring));
+    }
+    else if EQ("newtable") {
+      lua_newtable(L1);
+    }
+    else if EQ("newthread") {
+      lua_newthread(L1);
+    }
+    else if EQ("resetthread") {
+      lua_pushinteger(L1, lua_resetthread(L1));  /* deprecated */
+    }
+    else if EQ("newuserdata") {
+      lua_newuserdata(L1, getnum);
+    }
+    else if EQ("next") {
+      lua_next(L1, -2);
+    }
+    else if EQ("objsize") {
+      lua_pushinteger(L1, lua_rawlen(L1, getindex));
+    }
+    else if EQ("pcall") {
+      int narg = getnum;
+      int nres = getnum;
+      status = lua_pcall(L1, narg, nres, getnum);
+    }
+    else if EQ("pcallk") {
+      int narg = getnum;
+      int nres = getnum;
+      int i = getindex;
+      status = lua_pcallk(L1, narg, nres, 0, i, Cfunck);
+    }
+    else if EQ("pop") {
+      lua_pop(L1, getnum);
+    }
+    else if EQ("printstack") {
+      int n = getnum;
+      if (n != 0) {
+        printf("%s\n", luaL_tolstring(L1, n, NULL));
+        lua_pop(L1, 1);
+      }
+      else printstack(L1);
+    }
+    else if EQ("print") {
+      const char *msg = getstring;
+      printf("%s\n", msg);
+    }
+    else if EQ("warningC") {
+      const char *msg = getstring;
+      lua_warning(L1, msg, 1);
+    }
+    else if EQ("warning") {
+      const char *msg = getstring;
+      lua_warning(L1, msg, 0);
+    }
+    else if EQ("pushbool") {
+      lua_pushboolean(L1, getnum);
+    }
+    else if EQ("pushcclosure") {
+      lua_pushcclosure(L1, testC, getnum);
+    }
+    else if EQ("pushint") {
+      lua_pushinteger(L1, getnum);
+    }
+    else if EQ("pushnil") {
+      lua_pushnil(L1);
+    }
+    else if EQ("pushnum") {
+      lua_pushnumber(L1, (lua_Number)getnum);
+    }
+    else if EQ("pushstatus") {
+      lua_pushstring(L1, statcodes[status]);
+    }
+    else if EQ("pushstring") {
+      lua_pushstring(L1, getstring);
+    }
+    else if EQ("pushupvalueindex") {
+      lua_pushinteger(L1, lua_upvalueindex(getnum));
+    }
+    else if EQ("pushvalue") {
+      lua_pushvalue(L1, getindex);
+    }
+    else if EQ("pushfstringI") {
+      lua_pushfstring(L1, lua_tostring(L, -2), (int)lua_tointeger(L, -1));
+    }
+    else if EQ("pushfstringS") {
+      lua_pushfstring(L1, lua_tostring(L, -2), lua_tostring(L, -1));
+    }
+    else if EQ("pushfstringP") {
+      lua_pushfstring(L1, lua_tostring(L, -2), lua_topointer(L, -1));
+    }
+    else if EQ("rawget") {
+      int t = getindex;
+      lua_rawget(L1, t);
+    }
+    else if EQ("rawgeti") {
+      int t = getindex;
+      lua_rawgeti(L1, t, getnum);
+    }
+    else if EQ("rawgetp") {
+      int t = getindex;
+      lua_rawgetp(L1, t, cast_voidp(cast_sizet(getnum)));
+    }
+    else if EQ("rawset") {
+      int t = getindex;
+      lua_rawset(L1, t);
+    }
+    else if EQ("rawseti") {
+      int t = getindex;
+      lua_rawseti(L1, t, getnum);
+    }
+    else if EQ("rawsetp") {
+      int t = getindex;
+      lua_rawsetp(L1, t, cast_voidp(cast_sizet(getnum)));
+    }
+    else if EQ("remove") {
+      lua_remove(L1, getnum);
+    }
+    else if EQ("replace") {
+      lua_replace(L1, getindex);
+    }
+    else if EQ("resume") {
+      int i = getindex;
+      int nres;
+      status = lua_resume(lua_tothread(L1, i), L, getnum, &nres);
+    }
+    else if EQ("return") {
+      int n = getnum;
+      if (L1 != L) {
+        int i;
+        for (i = 0; i < n; i++) {
+          int idx = -(n - i);
+          switch (lua_type(L1, idx)) {
+            case LUA_TBOOLEAN:
+              lua_pushboolean(L, lua_toboolean(L1, idx));
+              break;
+            default:
+              lua_pushstring(L, lua_tostring(L1, idx));
+              break;
+          }
+        }
+      }
+      return n;
+    }
+    else if EQ("rotate") {
+      int i = getindex;
+      lua_rotate(L1, i, getnum);
+    }
+    else if EQ("setfield") {
+      int t = getindex;
+      const char *s = getstring;
+      lua_setfield(L1, t, s);
+    }
+    else if EQ("seti") {
+      int t = getindex;
+      lua_seti(L1, t, getnum);
+    }
+    else if EQ("setglobal") {
+      const char *s = getstring;
+      lua_setglobal(L1, s);
+    }
+    else if EQ("sethook") {
+      int mask = getnum;
+      int count = getnum;
+      const char *s = getstring;
+      sethookaux(L1, mask, count, s);
+    }
+    else if EQ("setmetatable") {
+      int idx = getindex;
+      lua_setmetatable(L1, idx);
+    }
+    else if EQ("settable") {
+      lua_settable(L1, getindex);
+    }
+    else if EQ("settop") {
+      lua_settop(L1, getnum);
+    }
+    else if EQ("testudata") {
+      int i = getindex;
+      lua_pushboolean(L1, luaL_testudata(L1, i, getstring) != NULL);
+    }
+    else if EQ("error") {
+      lua_error(L1);
+    }
+    else if EQ("abort") {
+      abort();
+    }
+    else if EQ("throw") {
+#if defined(__cplusplus)
+static struct X { int x; } x;
+      throw x;
+#else
+      luaL_error(L1, "C++");
+#endif
+      break;
+    }
+    else if EQ("tobool") {
+      lua_pushboolean(L1, lua_toboolean(L1, getindex));
+    }
+    else if EQ("tocfunction") {
+      lua_pushcfunction(L1, lua_tocfunction(L1, getindex));
+    }
+    else if EQ("tointeger") {
+      lua_pushinteger(L1, lua_tointeger(L1, getindex));
+    }
+    else if EQ("tonumber") {
+      lua_pushnumber(L1, lua_tonumber(L1, getindex));
+    }
+    else if EQ("topointer") {
+      lua_pushlightuserdata(L1, cast_voidp(lua_topointer(L1, getindex)));
+    }
+    else if EQ("touserdata") {
+      lua_pushlightuserdata(L1, lua_touserdata(L1, getindex));
+    }
+    else if EQ("tostring") {
+      const char *s = lua_tostring(L1, getindex);
+      const char *s1 = lua_pushstring(L1, s);
+      cast_void(s1);  /* to avoid warnings */
+      lua_longassert((s == NULL && s1 == NULL) || strcmp(s, s1) == 0);
+    }
+    else if EQ("Ltolstring") {
+      luaL_tolstring(L1, getindex, NULL);
+    }
+    else if EQ("type") {
+      lua_pushstring(L1, luaL_typename(L1, getnum));
+    }
+    else if EQ("xmove") {
+      int f = getindex;
+      int t = getindex;
+      lua_State *fs = (f == 0) ? L1 : lua_tothread(L1, f);
+      lua_State *ts = (t == 0) ? L1 : lua_tothread(L1, t);
+      int n = getnum;
+      if (n == 0) n = lua_gettop(fs);
+      lua_xmove(fs, ts, n);
+    }
+    else if EQ("isyieldable") {
+      lua_pushboolean(L1, lua_isyieldable(lua_tothread(L1, getindex)));
+    }
+    else if EQ("yield") {
+      return lua_yield(L1, getnum);
+    }
+    else if EQ("yieldk") {
+      int nres = getnum;
+      int i = getindex;
+      return lua_yieldk(L1, nres, i, Cfunck);
+    }
+    else if EQ("toclose") {
+      lua_toclose(L1, getnum);
+    }
+    else if EQ("closeslot") {
+      lua_closeslot(L1, getnum);
+    }
+    else luaL_error(L, "unknown instruction %s", buff);
+  }
+  return 0;
+}
+
+
+static int testC (lua_State *L) {
+  lua_State *L1;
+  const char *pc;
+  if (lua_isuserdata(L, 1)) {
+    L1 = getstate(L);
+    pc = luaL_checkstring(L, 2);
+  }
+  else if (lua_isthread(L, 1)) {
+    L1 = lua_tothread(L, 1);
+    pc = luaL_checkstring(L, 2);
+  }
+  else {
+    L1 = L;
+    pc = luaL_checkstring(L, 1);
+  }
+  return runC(L, L1, pc);
+}
+
+
+static int Cfunc (lua_State *L) {
+  return runC(L, L, lua_tostring(L, lua_upvalueindex(1)));
+}
+
+
+static int Cfunck (lua_State *L, int status, lua_KContext ctx) {
+  lua_pushstring(L, statcodes[status]);
+  lua_setglobal(L, "status");
+  lua_pushinteger(L, ctx);
+  lua_setglobal(L, "ctx");
+  return runC(L, L, lua_tostring(L, ctx));
+}
+
+
+static int makeCfunc (lua_State *L) {
+  luaL_checkstring(L, 1);
+  lua_pushcclosure(L, Cfunc, lua_gettop(L));
+  return 1;
+}
+
+
+/* }====================================================== */
+
+
+/*
+** {======================================================
+** tests for C hooks
+** =======================================================
+*/
+
+/*
+** C hook that runs the C script stored in registry.C_HOOK[L]
+*/
+static void Chook (lua_State *L, lua_Debug *ar) {
+  const char *scpt;
+  const char *const events [] = {"call", "ret", "line", "count", "tailcall"};
+  lua_getfield(L, LUA_REGISTRYINDEX, "C_HOOK");
+  lua_pushlightuserdata(L, L);
+  lua_gettable(L, -2);  /* get C_HOOK[L] (script saved by sethookaux) */
+  scpt = lua_tostring(L, -1);  /* not very religious (string will be popped) */
+  lua_pop(L, 2);  /* remove C_HOOK and script */
+  lua_pushstring(L, events[ar->event]);  /* may be used by script */
+  lua_pushinteger(L, ar->currentline);  /* may be used by script */
+  runC(L, L, scpt);  /* run script from C_HOOK[L] */
+}
+
+
+/*
+** sets 'registry.C_HOOK[L] = scpt' and sets 'Chook' as a hook
+*/
+static void sethookaux (lua_State *L, int mask, int count, const char *scpt) {
+  if (*scpt == '\0') {  /* no script? */
+    lua_sethook(L, NULL, 0, 0);  /* turn off hooks */
+    return;
+  }
+  lua_getfield(L, LUA_REGISTRYINDEX, "C_HOOK");  /* get C_HOOK table */
+  if (!lua_istable(L, -1)) {  /* no hook table? */
+    lua_pop(L, 1);  /* remove previous value */
+    lua_newtable(L);  /* create new C_HOOK table */
+    lua_pushvalue(L, -1);
+    lua_setfield(L, LUA_REGISTRYINDEX, "C_HOOK");  /* register it */
+  }
+  lua_pushlightuserdata(L, L);
+  lua_pushstring(L, scpt);
+  lua_settable(L, -3);  /* C_HOOK[L] = script */
+  lua_sethook(L, Chook, mask, count);
+}
+
+
+static int sethook (lua_State *L) {
+  if (lua_isnoneornil(L, 1))
+    lua_sethook(L, NULL, 0, 0);  /* turn off hooks */
+  else {
+    const char *scpt = luaL_checkstring(L, 1);
+    const char *smask = luaL_checkstring(L, 2);
+    int count = cast_int(luaL_optinteger(L, 3, 0));
+    int mask = 0;
+    if (strchr(smask, 'c')) mask |= LUA_MASKCALL;
+    if (strchr(smask, 'r')) mask |= LUA_MASKRET;
+    if (strchr(smask, 'l')) mask |= LUA_MASKLINE;
+    if (count > 0) mask |= LUA_MASKCOUNT;
+    sethookaux(L, mask, count, scpt);
+  }
+  return 0;
+}
+
+
+static int coresume (lua_State *L) {
+  int status, nres;
+  lua_State *co = lua_tothread(L, 1);
+  luaL_argcheck(L, co, 1, "coroutine expected");
+  status = lua_resume(co, L, 0, &nres);
+  if (status != LUA_OK && status != LUA_YIELD) {
+    lua_pushboolean(L, 0);
+    lua_insert(L, -2);
+    return 2;  /* return false + error message */
+  }
+  else {
+    lua_pushboolean(L, 1);
+    return 1;
+  }
+}
+
+/* }====================================================== */
+
+
+
+static const struct luaL_Reg tests_funcs[] = {
+  {"checkmemory", lua_checkmemory},
+  {"closestate", closestate},
+  {"d2s", d2s},
+  {"doonnewstack", doonnewstack},
+  {"doremote", doremote},
+  {"gccolor", gc_color},
+  {"gcage", gc_age},
+  {"gcstate", gc_state},
+  {"pobj", gc_printobj},
+  {"getref", getref},
+  {"hash", hash_query},
+  {"log2", log2_aux},
+  {"limits", get_limits},
+  {"listcode", listcode},
+  {"printcode", printcode},
+  {"listk", listk},
+  {"listabslineinfo", listabslineinfo},
+  {"listlocals", listlocals},
+  {"loadlib", loadlib},
+  {"checkpanic", checkpanic},
+  {"newstate", newstate},
+  {"newuserdata", newuserdata},
+  {"num2int", num2int},
+  {"pushuserdata", pushuserdata},
+  {"querystr", string_query},
+  {"querytab", table_query},
+  {"ref", tref},
+  {"resume", coresume},
+  {"s2d", s2d},
+  {"sethook", sethook},
+  {"stacklevel", stacklevel},
+  {"testC", testC},
+  {"makeCfunc", makeCfunc},
+  {"totalmem", mem_query},
+  {"alloccount", alloc_count},
+  {"allocfailnext", alloc_failnext},
+  {"trick", settrick},
+  {"udataval", udataval},
+  {"unref", unref},
+  {"upvalue", upvalue},
+  {NULL, NULL}
+};
+
+
+static void checkfinalmem (void) {
+  lua_assert(l_memcontrol.numblocks == 0);
+  lua_assert(l_memcontrol.total == 0);
+}
+
+
+int luaB_opentests (lua_State *L) {
+  void *ud;
+  lua_Alloc f = lua_getallocf(L, &ud);
+  lua_atpanic(L, &tpanic);
+  lua_setwarnf(L, &warnf, L);
+  lua_pushboolean(L, 0);
+  lua_setglobal(L, "_WARN");  /* _WARN = false */
+  regcodes(L);
+  atexit(checkfinalmem);
+  lua_assert(f == debug_realloc && ud == cast_voidp(&l_memcontrol));
+  lua_setallocf(L, f, ud);  /* exercise this function */
+  luaL_newlib(L, tests_funcs);
+  return 1;
+}
+
+#endif
+
diff --git a/src/ltests.h b/src/ltests.h
new file mode 100644
index 000000000000..ec520498bde4
--- /dev/null
+++ b/src/ltests.h
@@ -0,0 +1,151 @@
+/*
+** $Id: ltests.h $
+** Internal Header for Debugging of the Lua Implementation
+** See Copyright Notice in lua.h
+*/
+
+#ifndef ltests_h
+#define ltests_h
+
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/* test Lua with compatibility code */
+#define LUA_COMPAT_MATHLIB
+#define LUA_COMPAT_LT_LE
+
+
+#define LUA_DEBUG
+
+
+/* turn on assertions */
+#define LUAI_ASSERT
+
+
+/* to avoid warnings, and to make sure value is really unused */
+#define UNUSED(x)       (x=0, (void)(x))
+
+
+/* test for sizes in 'l_sprintf' (make sure whole buffer is available) */
+#undef l_sprintf
+#if !defined(LUA_USE_C89)
+#define l_sprintf(s,sz,f,i)	(memset(s,0xAB,sz), snprintf(s,sz,f,i))
+#else
+#define l_sprintf(s,sz,f,i)	(memset(s,0xAB,sz), sprintf(s,f,i))
+#endif
+
+
+/* get a chance to test code without jump tables */
+#define LUA_USE_JUMPTABLE	0
+
+
+/* use 32-bit integers in random generator */
+#define LUA_RAND32
+
+
+/* memory-allocator control variables */
+typedef struct Memcontrol {
+  int failnext;
+  unsigned long numblocks;
+  unsigned long total;
+  unsigned long maxmem;
+  unsigned long memlimit;
+  unsigned long countlimit;
+  unsigned long objcount[LUA_NUMTYPES];
+} Memcontrol;
+
+LUA_API Memcontrol l_memcontrol;
+
+
+/*
+** generic variable for debug tricks
+*/
+extern void *l_Trick;
+
+
+
+/*
+** Function to traverse and check all memory used by Lua
+*/
+LUAI_FUNC int lua_checkmemory (lua_State *L);
+
+/*
+** Function to print an object GC-friendly
+*/
+struct GCObject;
+LUAI_FUNC void lua_printobj (lua_State *L, struct GCObject *o);
+
+
+/* test for lock/unlock */
+
+struct L_EXTRA { int lock; int *plock; };
+#undef LUA_EXTRASPACE
+#define LUA_EXTRASPACE	sizeof(struct L_EXTRA)
+#define getlock(l)	cast(struct L_EXTRA*, lua_getextraspace(l))
+#define luai_userstateopen(l)  \
+	(getlock(l)->lock = 0, getlock(l)->plock = &(getlock(l)->lock))
+#define luai_userstateclose(l)  \
+  lua_assert(getlock(l)->lock == 1 && getlock(l)->plock == &(getlock(l)->lock))
+#define luai_userstatethread(l,l1) \
+  lua_assert(getlock(l1)->plock == getlock(l)->plock)
+#define luai_userstatefree(l,l1) \
+  lua_assert(getlock(l)->plock == getlock(l1)->plock)
+#define lua_lock(l)     lua_assert((*getlock(l)->plock)++ == 0)
+#define lua_unlock(l)   lua_assert(--(*getlock(l)->plock) == 0)
+
+
+
+LUA_API int luaB_opentests (lua_State *L);
+
+LUA_API void *debug_realloc (void *ud, void *block,
+                             size_t osize, size_t nsize);
+
+#if defined(lua_c)
+#define luaL_newstate()		lua_newstate(debug_realloc, &l_memcontrol)
+#define luaL_openlibs(L)  \
+  { (luaL_openlibs)(L); \
+     luaL_requiref(L, "T", luaB_opentests, 1); \
+     lua_pop(L, 1); }
+#endif
+
+
+
+/* change some sizes to give some bugs a chance */
+
+#undef LUAL_BUFFERSIZE
+#define LUAL_BUFFERSIZE		23
+#define MINSTRTABSIZE		2
+#define MAXIWTHABS		3
+
+#define STRCACHE_N	23
+#define STRCACHE_M	5
+
+#undef LUAI_USER_ALIGNMENT_T
+#define LUAI_USER_ALIGNMENT_T   union { char b[sizeof(void*) * 8]; }
+
+
+/*
+** This one is not compatible with tests for opcode optimizations,
+** as it blocks some optimizations
+#define MAXINDEXRK	0
+*/
+
+
+/* make stack-overflow tests run faster */
+#undef LUAI_MAXSTACK
+#define LUAI_MAXSTACK   50000
+
+
+/* test mode uses more stack space */
+#undef LUAI_MAXCCALLS
+#define LUAI_MAXCCALLS	180
+
+
+/* force Lua to use its own implementations */
+#undef lua_strx2number
+#undef lua_number2strx
+
+
+#endif
+
diff --git a/src/ltm.c b/src/ltm.c
index b657b783a801..07a060811d5c 100644
--- a/src/ltm.c
+++ b/src/ltm.c
@@ -102,12 +102,12 @@ const char *luaT_objtypename (lua_State *L, const TValue *o) {
 
 void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
                   const TValue *p2, const TValue *p3) {
-  StkId func = L->top;
+  StkId func = L->top.p;
   setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
   setobj2s(L, func + 1, p1);  /* 1st argument */
   setobj2s(L, func + 2, p2);  /* 2nd argument */
   setobj2s(L, func + 3, p3);  /* 3rd argument */
-  L->top = func + 4;
+  L->top.p = func + 4;
   /* metamethod may yield only when called from Lua code */
   if (isLuacode(L->ci))
     luaD_call(L, func, 0);
@@ -119,18 +119,18 @@ void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
 void luaT_callTMres (lua_State *L, const TValue *f, const TValue *p1,
                      const TValue *p2, StkId res) {
   ptrdiff_t result = savestack(L, res);
-  StkId func = L->top;
+  StkId func = L->top.p;
   setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
   setobj2s(L, func + 1, p1);  /* 1st argument */
   setobj2s(L, func + 2, p2);  /* 2nd argument */
-  L->top += 3;
+  L->top.p += 3;
   /* metamethod may yield only when called from Lua code */
   if (isLuacode(L->ci))
     luaD_call(L, func, 1);
   else
     luaD_callnoyield(L, func, 1);
   res = restorestack(L, result);
-  setobjs2s(L, res, --L->top);  /* move result to its place */
+  setobjs2s(L, res, --L->top.p);  /* move result to its place */
 }
 
 
@@ -165,7 +165,7 @@ void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
 
 
 void luaT_tryconcatTM (lua_State *L) {
-  StkId top = L->top;
+  StkId top = L->top.p;
   if (l_unlikely(!callbinTM(L, s2v(top - 2), s2v(top - 1), top - 2,
                                TM_CONCAT)))
     luaG_concaterror(L, s2v(top - 2), s2v(top - 1));
@@ -200,15 +200,15 @@ void luaT_trybiniTM (lua_State *L, const TValue *p1, lua_Integer i2,
 */
 int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
                       TMS event) {
-  if (callbinTM(L, p1, p2, L->top, event))  /* try original event */
-    return !l_isfalse(s2v(L->top));
+  if (callbinTM(L, p1, p2, L->top.p, event))  /* try original event */
+    return !l_isfalse(s2v(L->top.p));
 #if defined(LUA_COMPAT_LT_LE)
   else if (event == TM_LE) {
       /* try '!(p2 < p1)' for '(p1 <= p2)' */
       L->ci->callstatus |= CIST_LEQ;  /* mark it is doing 'lt' for 'le' */
-      if (callbinTM(L, p2, p1, L->top, TM_LT)) {
+      if (callbinTM(L, p2, p1, L->top.p, TM_LT)) {
         L->ci->callstatus ^= CIST_LEQ;  /* clear mark */
-        return l_isfalse(s2v(L->top));
+        return l_isfalse(s2v(L->top.p));
       }
       /* else error will remove this 'ci'; no need to clear mark */
   }
@@ -238,20 +238,20 @@ int luaT_callorderiTM (lua_State *L, const TValue *p1, int v2,
 void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
                          const Proto *p) {
   int i;
-  int actual = cast_int(L->top - ci->func) - 1;  /* number of arguments */
+  int actual = cast_int(L->top.p - ci->func.p) - 1;  /* number of arguments */
   int nextra = actual - nfixparams;  /* number of extra arguments */
   ci->u.l.nextraargs = nextra;
   luaD_checkstack(L, p->maxstacksize + 1);
   /* copy function to the top of the stack */
-  setobjs2s(L, L->top++, ci->func);
+  setobjs2s(L, L->top.p++, ci->func.p);
   /* move fixed parameters to the top of the stack */
   for (i = 1; i <= nfixparams; i++) {
-    setobjs2s(L, L->top++, ci->func + i);
-    setnilvalue(s2v(ci->func + i));  /* erase original parameter (for GC) */
+    setobjs2s(L, L->top.p++, ci->func.p + i);
+    setnilvalue(s2v(ci->func.p + i));  /* erase original parameter (for GC) */
   }
-  ci->func += actual + 1;
-  ci->top += actual + 1;
-  lua_assert(L->top <= ci->top && ci->top <= L->stack_last);
+  ci->func.p += actual + 1;
+  ci->top.p += actual + 1;
+  lua_assert(L->top.p <= ci->top.p && ci->top.p <= L->stack_last.p);
 }
 
 
@@ -261,10 +261,10 @@ void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
   if (wanted < 0) {
     wanted = nextra;  /* get all extra arguments available */
     checkstackGCp(L, nextra, where);  /* ensure stack space */
-    L->top = where + nextra;  /* next instruction will need top */
+    L->top.p = where + nextra;  /* next instruction will need top */
   }
   for (i = 0; i < wanted && i < nextra; i++)
-    setobjs2s(L, where + i, ci->func - nextra + i);
+    setobjs2s(L, where + i, ci->func.p - nextra + i);
   for (; i < wanted; i++)   /* complete required results with nil */
     setnilvalue(s2v(where + i));
 }
diff --git a/src/ltm.h b/src/ltm.h
index 73b833c605da..c309e2ae10e3 100644
--- a/src/ltm.h
+++ b/src/ltm.h
@@ -9,6 +9,7 @@
 
 
 #include "lobject.h"
+#include "lstate.h"
 
 
 /*
@@ -95,8 +96,8 @@ LUAI_FUNC int luaT_callorderiTM (lua_State *L, const TValue *p1, int v2,
                                  int inv, int isfloat, TMS event);
 
 LUAI_FUNC void luaT_adjustvarargs (lua_State *L, int nfixparams,
-                                   struct CallInfo *ci, const Proto *p);
-LUAI_FUNC void luaT_getvarargs (lua_State *L, struct CallInfo *ci,
+                                   CallInfo *ci, const Proto *p);
+LUAI_FUNC void luaT_getvarargs (lua_State *L, CallInfo *ci,
                                               StkId where, int wanted);
 
 
diff --git a/src/lua.c b/src/lua.c
index 0f1900444499..0ff884545304 100644
--- a/src/lua.c
+++ b/src/lua.c
@@ -177,10 +177,11 @@ static void print_version (void) {
 ** to the script (everything after 'script') go to positive indices;
 ** other arguments (before the script name) go to negative indices.
 ** If there is no script name, assume interpreter's name as base.
+** (If there is no interpreter's name either, 'script' is -1, so
+** table sizes are zero.)
 */
 static void createargtable (lua_State *L, char **argv, int argc, int script) {
   int i, narg;
-  if (script == argc) script = 0;  /* no script name? */
   narg = argc - (script + 1);  /* number of positive indices */
   lua_createtable(L, narg, script + 1);
   for (i = 0; i < argc; i++) {
@@ -268,14 +269,23 @@ static int handle_script (lua_State *L, char **argv) {
 
 /*
 ** Traverses all arguments from 'argv', returning a mask with those
-** needed before running any Lua code (or an error code if it finds
-** any invalid argument). 'first' returns the first not-handled argument
-** (either the script name or a bad argument in case of error).
+** needed before running any Lua code or an error code if it finds any
+** invalid argument. In case of error, 'first' is the index of the bad
+** argument.  Otherwise, 'first' is -1 if there is no program name,
+** 0 if there is no script name, or the index of the script name.
 */
 static int collectargs (char **argv, int *first) {
   int args = 0;
   int i;
-  for (i = 1; argv[i] != NULL; i++) {
+  if (argv[0] != NULL) {  /* is there a program name? */
+    if (argv[0][0])  /* not empty? */
+      progname = argv[0];  /* save it */
+  }
+  else {  /* no program name */
+    *first = -1;
+    return 0;
+  }
+  for (i = 1; argv[i] != NULL; i++) {  /* handle arguments */
     *first = i;
     if (argv[i][0] != '-')  /* not an option? */
         return args;  /* stop handling options */
@@ -316,7 +326,7 @@ static int collectargs (char **argv, int *first) {
         return has_error;
     }
   }
-  *first = i;  /* no script name */
+  *first = 0;  /* no script name */
   return args;
 }
 
@@ -609,8 +619,8 @@ static int pmain (lua_State *L) {
   char **argv = (char **)lua_touserdata(L, 2);
   int script;
   int args = collectargs(argv, &script);
+  int optlim = (script > 0) ? script : argc; /* first argv not an option */
   luaL_checkversion(L);  /* check that interpreter has correct version */
-  if (argv[0] && argv[0][0]) progname = argv[0];
   if (args == has_error) {  /* bad arg? */
     print_usage(argv[script]);  /* 'script' has index of bad arg. */
     return 0;
@@ -623,19 +633,21 @@ static int pmain (lua_State *L) {
   }
   luaL_openlibs(L);  /* open standard libraries */
   createargtable(L, argv, argc, script);  /* create table 'arg' */
-  lua_gc(L, LUA_GCGEN, 0, 0);  /* GC in generational mode */
+  lua_gc(L, LUA_GCRESTART);  /* start GC... */
+  lua_gc(L, LUA_GCGEN, 0, 0);  /* ...in generational mode */
   if (!(args & has_E)) {  /* no option '-E'? */
     if (handle_luainit(L) != LUA_OK)  /* run LUA_INIT */
       return 0;  /* error running LUA_INIT */
   }
-  if (!runargs(L, argv, script))  /* execute arguments -e and -l */
+  if (!runargs(L, argv, optlim))  /* execute arguments -e and -l */
     return 0;  /* something failed */
-  if (script < argc &&  /* execute main script (if there is one) */
-      handle_script(L, argv + script) != LUA_OK)
-    return 0;
+  if (script > 0) {  /* execute main script (if there is one) */
+    if (handle_script(L, argv + script) != LUA_OK)
+      return 0;  /* interrupt in case of error */
+  }
   if (args & has_i)  /* -i option? */
     doREPL(L);  /* do read-eval-print loop */
-  else if (script == argc && !(args & (has_e | has_v))) {  /* no arguments? */
+  else if (script < 1 && !(args & (has_e | has_v))) { /* no active option? */
     if (lua_stdin_is_tty()) {  /* running in interactive mode? */
       print_version();
       doREPL(L);  /* do read-eval-print loop */
@@ -654,6 +666,7 @@ int main (int argc, char **argv) {
     l_message(argv[0], "cannot create state: not enough memory");
     return EXIT_FAILURE;
   }
+  lua_gc(L, LUA_GCSTOP);  /* stop GC while building state */
   lua_pushcfunction(L, &pmain);  /* to call 'pmain' in protected mode */
   lua_pushinteger(L, argc);  /* 1st argument */
   lua_pushlightuserdata(L, argv); /* 2nd argument */
diff --git a/src/lua.h b/src/lua.h
index e6618392cc7e..fd16cf8050b8 100644
--- a/src/lua.h
+++ b/src/lua.h
@@ -18,14 +18,14 @@
 
 #define LUA_VERSION_MAJOR	"5"
 #define LUA_VERSION_MINOR	"4"
-#define LUA_VERSION_RELEASE	"4"
+#define LUA_VERSION_RELEASE	"6"
 
 #define LUA_VERSION_NUM			504
-#define LUA_VERSION_RELEASE_NUM		(LUA_VERSION_NUM * 100 + 4)
+#define LUA_VERSION_RELEASE_NUM		(LUA_VERSION_NUM * 100 + 6)
 
 #define LUA_VERSION	"Lua " LUA_VERSION_MAJOR "." LUA_VERSION_MINOR
 #define LUA_RELEASE	LUA_VERSION "." LUA_VERSION_RELEASE
-#define LUA_COPYRIGHT	LUA_RELEASE "  Copyright (C) 1994-2022 Lua.org, PUC-Rio"
+#define LUA_COPYRIGHT	LUA_RELEASE "  Copyright (C) 1994-2023 Lua.org, PUC-Rio"
 #define LUA_AUTHORS	"R. Ierusalimschy, L. H. de Figueiredo, W. Celes"
 
 
@@ -131,6 +131,16 @@ typedef void * (*lua_Alloc) (void *ud, void *ptr, size_t osize, size_t nsize);
 typedef void (*lua_WarnFunction) (void *ud, const char *msg, int tocont);
 
 
+/*
+** Type used by the debug API to collect debug information
+*/
+typedef struct lua_Debug lua_Debug;
+
+
+/*
+** Functions to be called by the debugger in specific events
+*/
+typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);
 
 
 /*
@@ -153,7 +163,8 @@ extern const char lua_ident[];
 LUA_API lua_State *(lua_newstate) (lua_Alloc f, void *ud);
 LUA_API void       (lua_close) (lua_State *L);
 LUA_API lua_State *(lua_newthread) (lua_State *L);
-LUA_API int        (lua_resetthread) (lua_State *L);
+LUA_API int        (lua_closethread) (lua_State *L, lua_State *from);
+LUA_API int        (lua_resetthread) (lua_State *L);  /* Deprecated! */
 
 LUA_API lua_CFunction (lua_atpanic) (lua_State *L, lua_CFunction panicf);
 
@@ -442,12 +453,6 @@ LUA_API void (lua_closeslot) (lua_State *L, int idx);
 #define LUA_MASKLINE	(1 << LUA_HOOKLINE)
 #define LUA_MASKCOUNT	(1 << LUA_HOOKCOUNT)
 
-typedef struct lua_Debug lua_Debug;  /* activation record */
-
-
-/* Functions to be called by the debugger in specific events */
-typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);
-
 
 LUA_API int (lua_getstack) (lua_State *L, int level, lua_Debug *ar);
 LUA_API int (lua_getinfo) (lua_State *L, const char *what, lua_Debug *ar);
@@ -492,7 +497,7 @@ struct lua_Debug {
 
 
 /******************************************************************************
-* Copyright (C) 1994-2022 Lua.org, PUC-Rio.
+* Copyright (C) 1994-2023 Lua.org, PUC-Rio.
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
diff --git a/src/luac.c b/src/luac.c
index f6db9cf656bb..5f4a141bddd9 100644
--- a/src/luac.c
+++ b/src/luac.c
@@ -121,7 +121,7 @@ static int doargs(int argc, char* argv[])
  return i;
 }
 
-#define FUNCTION "(function()end)();"
+#define FUNCTION "(function()end)();\n"
 
 static const char* reader(lua_State* L, void* ud, size_t* size)
 {
@@ -138,7 +138,7 @@ static const char* reader(lua_State* L, void* ud, size_t* size)
  }
 }
 
-#define toproto(L,i) getproto(s2v(L->top+(i)))
+#define toproto(L,i) getproto(s2v(L->top.p+(i)))
 
 static const Proto* combine(lua_State* L, int n)
 {
@@ -155,8 +155,6 @@ static const Proto* combine(lua_State* L, int n)
    f->p[i]=toproto(L,i-n-1);
    if (f->p[i]->sizeupvalues>0) f->p[i]->upvalues[0].instack=0;
   }
-  luaM_freearray(L,f->lineinfo,f->sizelineinfo);
-  f->sizelineinfo=0;
   return f;
  }
 }
diff --git a/src/luaconf.h b/src/luaconf.h
index d42d14b7d5f1..137103edec4e 100644
--- a/src/luaconf.h
+++ b/src/luaconf.h
@@ -70,6 +70,12 @@
 #endif
 
 
+#if defined(LUA_USE_IOS)
+#define LUA_USE_POSIX
+#define LUA_USE_DLOPEN
+#endif
+
+
 /*
 @@ LUAI_IS32INT is true iff 'int' has (at least) 32 bits.
 */
@@ -728,7 +734,7 @@
 ** CHANGE it if you need a different limit. This limit is arbitrary;
 ** its only purpose is to stop Lua from consuming unlimited stack
 ** space (and to reserve some numbers for pseudo-indices).
-** (It must fit into max(size_t)/32.)
+** (It must fit into max(size_t)/32 and max(int)/2.)
 */
 #if LUAI_IS32INT
 #define LUAI_MAXSTACK		1000000
@@ -747,14 +753,15 @@
 
 /*
 @@ LUA_IDSIZE gives the maximum size for the description of the source
-@@ of a function in debug information.
+** of a function in debug information.
 ** CHANGE it if you want a different size.
 */
 #define LUA_IDSIZE	60
 
 
 /*
-@@ LUAL_BUFFERSIZE is the buffer size used by the lauxlib buffer system.
+@@ LUAL_BUFFERSIZE is the initial buffer size used by the lauxlib
+** buffer system.
 */
 #define LUAL_BUFFERSIZE   ((int)(16 * sizeof(void*) * sizeof(lua_Number)))
 
diff --git a/src/lundump.c b/src/lundump.c
index 5aa55c445789..02aed64fb622 100644
--- a/src/lundump.c
+++ b/src/lundump.c
@@ -120,10 +120,10 @@ static TString *loadStringN (LoadState *S, Proto *p) {
   }
   else {  /* long string */
     ts = luaS_createlngstrobj(L, size);  /* create string */
-    setsvalue2s(L, L->top, ts);  /* anchor it ('loadVector' can GC) */
+    setsvalue2s(L, L->top.p, ts);  /* anchor it ('loadVector' can GC) */
     luaD_inctop(L);
     loadVector(S, getstr(ts), size);  /* load directly in final place */
-    L->top--;  /* pop string */
+    L->top.p--;  /* pop string */
   }
   luaC_objbarrier(L, p, ts);
   return ts;
@@ -248,6 +248,8 @@ static void loadDebug (LoadState *S, Proto *f) {
     f->locvars[i].endpc = loadInt(S);
   }
   n = loadInt(S);
+  if (n != 0)  /* does it have debug information? */
+    n = f->sizeupvalues;  /* must be this many */
   for (i = 0; i < n; i++)
     f->upvalues[i].name = loadStringN(S, f);
 }
@@ -321,7 +323,7 @@ LClosure *luaU_undump(lua_State *L, ZIO *Z, const char *name) {
   S.Z = Z;
   checkHeader(&S);
   cl = luaF_newLclosure(L, loadByte(&S));
-  setclLvalue2s(L, L->top, cl);
+  setclLvalue2s(L, L->top.p, cl);
   luaD_inctop(L);
   cl->p = luaF_newproto(L);
   luaC_objbarrier(L, cl, cl->p);
diff --git a/src/lutf8lib.c b/src/lutf8lib.c
index e7bf098f6d04..3a5b9bc38a5b 100644
--- a/src/lutf8lib.c
+++ b/src/lutf8lib.c
@@ -25,6 +25,9 @@
 
 #define MAXUTF		0x7FFFFFFFu
 
+
+#define MSGInvalid	"invalid UTF-8 code"
+
 /*
 ** Integer type for decoded UTF-8 values; MAXUTF needs 31 bits.
 */
@@ -35,7 +38,8 @@ typedef unsigned long utfint;
 #endif
 
 
-#define iscont(p)	((*(p) & 0xC0) == 0x80)
+#define iscont(c)	(((c) & 0xC0) == 0x80)
+#define iscontp(p)	iscont(*(p))
 
 
 /* from strlib */
@@ -65,7 +69,7 @@ static const char *utf8_decode (const char *s, utfint *val, int strict) {
     int count = 0;  /* to count number of continuation bytes */
     for (; c & 0x40; c <<= 1) {  /* while it needs continuation bytes... */
       unsigned int cc = (unsigned char)s[++count];  /* read next byte */
-      if ((cc & 0xC0) != 0x80)  /* not a continuation byte? */
+      if (!iscont(cc))  /* not a continuation byte? */
         return NULL;  /* invalid byte sequence */
       res = (res << 6) | (cc & 0x3F);  /* add lower 6 bits from cont. byte */
     }
@@ -140,7 +144,7 @@ static int codepoint (lua_State *L) {
     utfint code;
     s = utf8_decode(s, &code, !lax);
     if (s == NULL)
-      return luaL_error(L, "invalid UTF-8 code");
+      return luaL_error(L, MSGInvalid);
     lua_pushinteger(L, code);
     n++;
   }
@@ -190,16 +194,16 @@ static int byteoffset (lua_State *L) {
                    "position out of bounds");
   if (n == 0) {
     /* find beginning of current byte sequence */
-    while (posi > 0 && iscont(s + posi)) posi--;
+    while (posi > 0 && iscontp(s + posi)) posi--;
   }
   else {
-    if (iscont(s + posi))
+    if (iscontp(s + posi))
       return luaL_error(L, "initial position is a continuation byte");
     if (n < 0) {
        while (n < 0 && posi > 0) {  /* move back */
          do {  /* find beginning of previous character */
            posi--;
-         } while (posi > 0 && iscont(s + posi));
+         } while (posi > 0 && iscontp(s + posi));
          n++;
        }
      }
@@ -208,7 +212,7 @@ static int byteoffset (lua_State *L) {
        while (n > 0 && posi < (lua_Integer)len) {
          do {  /* find beginning of next character */
            posi++;
-         } while (iscont(s + posi));  /* (cannot pass final '\0') */
+         } while (iscontp(s + posi));  /* (cannot pass final '\0') */
          n--;
        }
      }
@@ -226,15 +230,15 @@ static int iter_aux (lua_State *L, int strict) {
   const char *s = luaL_checklstring(L, 1, &len);
   lua_Unsigned n = (lua_Unsigned)lua_tointeger(L, 2);
   if (n < len) {
-    while (iscont(s + n)) n++;  /* skip continuation bytes */
+    while (iscontp(s + n)) n++;  /* go to next character */
   }
   if (n >= len)  /* (also handles original 'n' being negative) */
     return 0;  /* no more codepoints */
   else {
     utfint code;
     const char *next = utf8_decode(s + n, &code, strict);
-    if (next == NULL)
-      return luaL_error(L, "invalid UTF-8 code");
+    if (next == NULL || iscontp(next))
+      return luaL_error(L, MSGInvalid);
     lua_pushinteger(L, n + 1);
     lua_pushinteger(L, code);
     return 2;
@@ -253,7 +257,8 @@ static int iter_auxlax (lua_State *L) {
 
 static int iter_codes (lua_State *L) {
   int lax = lua_toboolean(L, 2);
-  luaL_checkstring(L, 1);
+  const char *s = luaL_checkstring(L, 1);
+  luaL_argcheck(L, !iscontp(s), 1, MSGInvalid);
   lua_pushcfunction(L, lax ? iter_auxlax : iter_auxstrict);
   lua_pushvalue(L, 1);
   lua_pushinteger(L, 0);
diff --git a/src/lvm.c b/src/lvm.c
index 2ec344003194..8493a770c56f 100644
--- a/src/lvm.c
+++ b/src/lvm.c
@@ -608,8 +608,8 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
   if (tm == NULL)  /* no TM? */
     return 0;  /* objects are different */
   else {
-    luaT_callTMres(L, tm, t1, t2, L->top);  /* call TM */
-    return !l_isfalse(s2v(L->top));
+    luaT_callTMres(L, tm, t1, t2, L->top.p);  /* call TM */
+    return !l_isfalse(s2v(L->top.p));
   }
 }
 
@@ -633,17 +633,17 @@ static void copy2buff (StkId top, int n, char *buff) {
 
 /*
 ** Main operation for concatenation: concat 'total' values in the stack,
-** from 'L->top - total' up to 'L->top - 1'.
+** from 'L->top.p - total' up to 'L->top.p - 1'.
 */
 void luaV_concat (lua_State *L, int total) {
   if (total == 1)
     return;  /* "all" values already concatenated */
   do {
-    StkId top = L->top;
+    StkId top = L->top.p;
     int n = 2;  /* number of elements handled in this pass (at least 2) */
     if (!(ttisstring(s2v(top - 2)) || cvt2str(s2v(top - 2))) ||
         !tostring(L, s2v(top - 1)))
-      luaT_tryconcatTM(L);
+      luaT_tryconcatTM(L);  /* may invalidate 'top' */
     else if (isemptystr(s2v(top - 1)))  /* second operand is empty? */
       cast_void(tostring(L, s2v(top - 2)));  /* result is first operand */
     else if (isemptystr(s2v(top - 2))) {  /* first operand is empty string? */
@@ -656,8 +656,10 @@ void luaV_concat (lua_State *L, int total) {
       /* collect total length and number of strings */
       for (n = 1; n < total && tostring(L, s2v(top - n - 1)); n++) {
         size_t l = vslen(s2v(top - n - 1));
-        if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl))
+        if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) {
+          L->top.p = top - total;  /* pop strings to avoid wasting stack */
           luaG_runerror(L, "string length overflow");
+        }
         tl += l;
       }
       if (tl <= LUAI_MAXSHORTLEN) {  /* is result a short string? */
@@ -671,8 +673,8 @@ void luaV_concat (lua_State *L, int total) {
       }
       setsvalue2s(L, top - n, ts);  /* create result */
     }
-    total -= n-1;  /* got 'n' strings to create 1 new */
-    L->top -= n-1;  /* popped 'n' strings and pushed one */
+    total -= n - 1;  /* got 'n' strings to create one new */
+    L->top.p -= n - 1;  /* popped 'n' strings and pushed one */
   } while (total > 1);  /* repeat until only 1 result left */
 }
 
@@ -763,12 +765,10 @@ lua_Number luaV_modf (lua_State *L, lua_Number m, lua_Number n) {
 /* number of bits in an integer */
 #define NBITS	cast_int(sizeof(lua_Integer) * CHAR_BIT)
 
+
 /*
 ** Shift left operation. (Shift right just negates 'y'.)
 */
-#define luaV_shiftr(x,y)	luaV_shiftl(x,intop(-, 0, y))
-
-
 lua_Integer luaV_shiftl (lua_Integer x, lua_Integer y) {
   if (y < 0) {  /* shift right? */
     if (y <= -NBITS) return 0;
@@ -808,26 +808,26 @@ static void pushclosure (lua_State *L, Proto *p, UpVal **encup, StkId base,
 */
 void luaV_finishOp (lua_State *L) {
   CallInfo *ci = L->ci;
-  StkId base = ci->func + 1;
+  StkId base = ci->func.p + 1;
   Instruction inst = *(ci->u.l.savedpc - 1);  /* interrupted instruction */
   OpCode op = GET_OPCODE(inst);
   switch (op) {  /* finish its execution */
     case OP_MMBIN: case OP_MMBINI: case OP_MMBINK: {
-      setobjs2s(L, base + GETARG_A(*(ci->u.l.savedpc - 2)), --L->top);
+      setobjs2s(L, base + GETARG_A(*(ci->u.l.savedpc - 2)), --L->top.p);
       break;
     }
     case OP_UNM: case OP_BNOT: case OP_LEN:
     case OP_GETTABUP: case OP_GETTABLE: case OP_GETI:
     case OP_GETFIELD: case OP_SELF: {
-      setobjs2s(L, base + GETARG_A(inst), --L->top);
+      setobjs2s(L, base + GETARG_A(inst), --L->top.p);
       break;
     }
     case OP_LT: case OP_LE:
     case OP_LTI: case OP_LEI:
     case OP_GTI: case OP_GEI:
     case OP_EQ: {  /* note that 'OP_EQI'/'OP_EQK' cannot yield */
-      int res = !l_isfalse(s2v(L->top - 1));
-      L->top--;
+      int res = !l_isfalse(s2v(L->top.p - 1));
+      L->top.p--;
 #if defined(LUA_COMPAT_LT_LE)
       if (ci->callstatus & CIST_LEQ) {  /* "<=" using "<" instead? */
         ci->callstatus ^= CIST_LEQ;  /* clear mark */
@@ -840,11 +840,11 @@ void luaV_finishOp (lua_State *L) {
       break;
     }
     case OP_CONCAT: {
-      StkId top = L->top - 1;  /* top when 'luaT_tryconcatTM' was called */
+      StkId top = L->top.p - 1;  /* top when 'luaT_tryconcatTM' was called */
       int a = GETARG_A(inst);      /* first element to concatenate */
       int total = cast_int(top - 1 - (base + a));  /* yet to concatenate */
       setobjs2s(L, top - 2, top);  /* put TM result in proper position */
-      L->top = top - 1;  /* top is one after last element (at top-2) */
+      L->top.p = top - 1;  /* top is one after last element (at top-2) */
       luaV_concat(L, total);  /* concat them (may yield again) */
       break;
     }
@@ -856,7 +856,7 @@ void luaV_finishOp (lua_State *L) {
       StkId ra = base + GETARG_A(inst);
       /* adjust top to signal correct number of returns, in case the
          return is "up to top" ('isIT') */
-      L->top = ra + ci->u2.nres;
+      L->top.p = ra + ci->u2.nres;
       /* repeat instruction to close other vars. and complete the return */
       ci->u.l.savedpc--;
       break;
@@ -898,6 +898,7 @@ void luaV_finishOp (lua_State *L) {
 ** operation, 'fop' is the float operation.
 */
 #define op_arithI(L,iop,fop) {  \
+  StkId ra = RA(i); \
   TValue *v1 = vRB(i);  \
   int imm = GETARG_sC(i);  \
   if (ttisinteger(v1)) {  \
@@ -926,6 +927,7 @@ void luaV_finishOp (lua_State *L) {
 ** Arithmetic operations over floats and others with register operands.
 */
 #define op_arithf(L,fop) {  \
+  StkId ra = RA(i); \
   TValue *v1 = vRB(i);  \
   TValue *v2 = vRC(i);  \
   op_arithf_aux(L, v1, v2, fop); }
@@ -935,6 +937,7 @@ void luaV_finishOp (lua_State *L) {
 ** Arithmetic operations with K operands for floats.
 */
 #define op_arithfK(L,fop) {  \
+  StkId ra = RA(i); \
   TValue *v1 = vRB(i);  \
   TValue *v2 = KC(i); lua_assert(ttisnumber(v2));  \
   op_arithf_aux(L, v1, v2, fop); }
@@ -944,6 +947,7 @@ void luaV_finishOp (lua_State *L) {
 ** Arithmetic operations over integers and floats.
 */
 #define op_arith_aux(L,v1,v2,iop,fop) {  \
+  StkId ra = RA(i); \
   if (ttisinteger(v1) && ttisinteger(v2)) {  \
     lua_Integer i1 = ivalue(v1); lua_Integer i2 = ivalue(v2);  \
     pc++; setivalue(s2v(ra), iop(L, i1, i2));  \
@@ -973,6 +977,7 @@ void luaV_finishOp (lua_State *L) {
 ** Bitwise operations with constant operand.
 */
 #define op_bitwiseK(L,op) {  \
+  StkId ra = RA(i); \
   TValue *v1 = vRB(i);  \
   TValue *v2 = KC(i);  \
   lua_Integer i1;  \
@@ -986,6 +991,7 @@ void luaV_finishOp (lua_State *L) {
 ** Bitwise operations with register operands.
 */
 #define op_bitwise(L,op) {  \
+  StkId ra = RA(i); \
   TValue *v1 = vRB(i);  \
   TValue *v2 = vRC(i);  \
   lua_Integer i1; lua_Integer i2;  \
@@ -1000,18 +1006,19 @@ void luaV_finishOp (lua_State *L) {
 ** integers.
 */
 #define op_order(L,opi,opn,other) {  \
-        int cond;  \
-        TValue *rb = vRB(i);  \
-        if (ttisinteger(s2v(ra)) && ttisinteger(rb)) {  \
-          lua_Integer ia = ivalue(s2v(ra));  \
-          lua_Integer ib = ivalue(rb);  \
-          cond = opi(ia, ib);  \
-        }  \
-        else if (ttisnumber(s2v(ra)) && ttisnumber(rb))  \
-          cond = opn(s2v(ra), rb);  \
-        else  \
-          Protect(cond = other(L, s2v(ra), rb));  \
-        docondjump(); }
+  StkId ra = RA(i); \
+  int cond;  \
+  TValue *rb = vRB(i);  \
+  if (ttisinteger(s2v(ra)) && ttisinteger(rb)) {  \
+    lua_Integer ia = ivalue(s2v(ra));  \
+    lua_Integer ib = ivalue(rb);  \
+    cond = opi(ia, ib);  \
+  }  \
+  else if (ttisnumber(s2v(ra)) && ttisnumber(rb))  \
+    cond = opn(s2v(ra), rb);  \
+  else  \
+    Protect(cond = other(L, s2v(ra), rb));  \
+  docondjump(); }
 
 
 /*
@@ -1019,20 +1026,21 @@ void luaV_finishOp (lua_State *L) {
 ** always small enough to have an exact representation as a float.)
 */
 #define op_orderI(L,opi,opf,inv,tm) {  \
-        int cond;  \
-        int im = GETARG_sB(i);  \
-        if (ttisinteger(s2v(ra)))  \
-          cond = opi(ivalue(s2v(ra)), im);  \
-        else if (ttisfloat(s2v(ra))) {  \
-          lua_Number fa = fltvalue(s2v(ra));  \
-          lua_Number fim = cast_num(im);  \
-          cond = opf(fa, fim);  \
-        }  \
-        else {  \
-          int isf = GETARG_C(i);  \
-          Protect(cond = luaT_callorderiTM(L, s2v(ra), im, inv, isf, tm));  \
-        }  \
-        docondjump(); }
+  StkId ra = RA(i); \
+  int cond;  \
+  int im = GETARG_sB(i);  \
+  if (ttisinteger(s2v(ra)))  \
+    cond = opi(ivalue(s2v(ra)), im);  \
+  else if (ttisfloat(s2v(ra))) {  \
+    lua_Number fa = fltvalue(s2v(ra));  \
+    lua_Number fim = cast_num(im);  \
+    cond = opf(fa, fim);  \
+  }  \
+  else {  \
+    int isf = GETARG_C(i);  \
+    Protect(cond = luaT_callorderiTM(L, s2v(ra), im, inv, isf, tm));  \
+  }  \
+  docondjump(); }
 
 /* }================================================================== */
 
@@ -1061,7 +1069,7 @@ void luaV_finishOp (lua_State *L) {
 
 #define updatetrap(ci)  (trap = ci->u.l.trap)
 
-#define updatebase(ci)	(base = ci->func + 1)
+#define updatebase(ci)	(base = ci->func.p + 1)
 
 
 #define updatestack(ci)  \
@@ -1096,7 +1104,7 @@ void luaV_finishOp (lua_State *L) {
 ** Whenever code can raise errors, the global 'pc' and the global
 ** 'top' must be correct to report occasional errors.
 */
-#define savestate(L,ci)		(savepc(L), L->top = ci->top)
+#define savestate(L,ci)		(savepc(L), L->top.p = ci->top.p)
 
 
 /*
@@ -1116,7 +1124,7 @@ void luaV_finishOp (lua_State *L) {
 
 /* 'c' is the limit of live values in the stack */
 #define checkGC(L,c)  \
-	{ luaC_condGC(L, (savepc(L), L->top = (c)), \
+	{ luaC_condGC(L, (savepc(L), L->top.p = (c)), \
                          updatetrap(ci)); \
            luai_threadyield(L); }
 
@@ -1128,7 +1136,6 @@ void luaV_finishOp (lua_State *L) {
     updatebase(ci);  /* correct stack */ \
   } \
   i = *(pc++); \
-  ra = RA(i); /* WARNING: any stack reallocation invalidates 'ra' */ \
 }
 
 #define vmdispatch(o)	switch(o)
@@ -1148,7 +1155,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
  startfunc:
   trap = L->hookmask;
  returning:  /* trap already set */
-  cl = clLvalue(s2v(ci->func));
+  cl = clLvalue(s2v(ci->func.p));
   k = cl->p->k;
   pc = ci->u.l.savedpc;
   if (l_unlikely(trap)) {
@@ -1160,60 +1167,68 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
     }
     ci->u.l.trap = 1;  /* assume trap is on, for now */
   }
-  base = ci->func + 1;
+  base = ci->func.p + 1;
   /* main loop of interpreter */
   for (;;) {
     Instruction i;  /* instruction being executed */
-    StkId ra;  /* instruction's A register */
     vmfetch();
     #if 0
       /* low-level line tracing for debugging Lua */
       printf("line: %d\n", luaG_getfuncline(cl->p, pcRel(pc, cl->p)));
     #endif
-    lua_assert(base == ci->func + 1);
-    lua_assert(base <= L->top && L->top < L->stack_last);
+    lua_assert(base == ci->func.p + 1);
+    lua_assert(base <= L->top.p && L->top.p <= L->stack_last.p);
     /* invalidate top for instructions not expecting it */
-    lua_assert(isIT(i) || (cast_void(L->top = base), 1));
+    lua_assert(isIT(i) || (cast_void(L->top.p = base), 1));
     vmdispatch (GET_OPCODE(i)) {
       vmcase(OP_MOVE) {
+        StkId ra = RA(i);
         setobjs2s(L, ra, RB(i));
         vmbreak;
       }
       vmcase(OP_LOADI) {
+        StkId ra = RA(i);
         lua_Integer b = GETARG_sBx(i);
         setivalue(s2v(ra), b);
         vmbreak;
       }
       vmcase(OP_LOADF) {
+        StkId ra = RA(i);
         int b = GETARG_sBx(i);
         setfltvalue(s2v(ra), cast_num(b));
         vmbreak;
       }
       vmcase(OP_LOADK) {
+        StkId ra = RA(i);
         TValue *rb = k + GETARG_Bx(i);
         setobj2s(L, ra, rb);
         vmbreak;
       }
       vmcase(OP_LOADKX) {
+        StkId ra = RA(i);
         TValue *rb;
         rb = k + GETARG_Ax(*pc); pc++;
         setobj2s(L, ra, rb);
         vmbreak;
       }
       vmcase(OP_LOADFALSE) {
+        StkId ra = RA(i);
         setbfvalue(s2v(ra));
         vmbreak;
       }
       vmcase(OP_LFALSESKIP) {
+        StkId ra = RA(i);
         setbfvalue(s2v(ra));
         pc++;  /* skip next instruction */
         vmbreak;
       }
       vmcase(OP_LOADTRUE) {
+        StkId ra = RA(i);
         setbtvalue(s2v(ra));
         vmbreak;
       }
       vmcase(OP_LOADNIL) {
+        StkId ra = RA(i);
         int b = GETARG_B(i);
         do {
           setnilvalue(s2v(ra++));
@@ -1221,19 +1236,22 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_GETUPVAL) {
+        StkId ra = RA(i);
         int b = GETARG_B(i);
-        setobj2s(L, ra, cl->upvals[b]->v);
+        setobj2s(L, ra, cl->upvals[b]->v.p);
         vmbreak;
       }
       vmcase(OP_SETUPVAL) {
+        StkId ra = RA(i);
         UpVal *uv = cl->upvals[GETARG_B(i)];
-        setobj(L, uv->v, s2v(ra));
+        setobj(L, uv->v.p, s2v(ra));
         luaC_barrier(L, uv, s2v(ra));
         vmbreak;
       }
       vmcase(OP_GETTABUP) {
+        StkId ra = RA(i);
         const TValue *slot;
-        TValue *upval = cl->upvals[GETARG_B(i)]->v;
+        TValue *upval = cl->upvals[GETARG_B(i)]->v.p;
         TValue *rc = KC(i);
         TString *key = tsvalue(rc);  /* key must be a string */
         if (luaV_fastget(L, upval, key, slot, luaH_getshortstr)) {
@@ -1244,6 +1262,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_GETTABLE) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = vRB(i);
         TValue *rc = vRC(i);
@@ -1258,6 +1277,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_GETI) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = vRB(i);
         int c = GETARG_C(i);
@@ -1272,6 +1292,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_GETFIELD) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = vRB(i);
         TValue *rc = KC(i);
@@ -1285,7 +1306,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       }
       vmcase(OP_SETTABUP) {
         const TValue *slot;
-        TValue *upval = cl->upvals[GETARG_A(i)]->v;
+        TValue *upval = cl->upvals[GETARG_A(i)]->v.p;
         TValue *rb = KB(i);
         TValue *rc = RKC(i);
         TString *key = tsvalue(rb);  /* key must be a string */
@@ -1297,6 +1318,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SETTABLE) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = vRB(i);  /* key (table is in 'ra') */
         TValue *rc = RKC(i);  /* value */
@@ -1311,6 +1333,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SETI) {
+        StkId ra = RA(i);
         const TValue *slot;
         int c = GETARG_B(i);
         TValue *rc = RKC(i);
@@ -1325,6 +1348,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SETFIELD) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = KB(i);
         TValue *rc = RKC(i);
@@ -1337,6 +1361,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_NEWTABLE) {
+        StkId ra = RA(i);
         int b = GETARG_B(i);  /* log2(hash size) + 1 */
         int c = GETARG_C(i);  /* array size */
         Table *t;
@@ -1346,7 +1371,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         if (TESTARG_k(i))  /* non-zero extra argument? */
           c += GETARG_Ax(*pc) * (MAXARG_C + 1);  /* add it to size */
         pc++;  /* skip extra argument */
-        L->top = ra + 1;  /* correct top in case of emergency GC */
+        L->top.p = ra + 1;  /* correct top in case of emergency GC */
         t = luaH_new(L);  /* memory allocation */
         sethvalue2s(L, ra, t);
         if (b != 0 || c != 0)
@@ -1355,6 +1380,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SELF) {
+        StkId ra = RA(i);
         const TValue *slot;
         TValue *rb = vRB(i);
         TValue *rc = RKC(i);
@@ -1384,6 +1410,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_MODK) {
+        savestate(L, ci);  /* in case of division by 0 */
         op_arithK(L, luaV_mod, luaV_modf);
         vmbreak;
       }
@@ -1396,6 +1423,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_IDIVK) {
+        savestate(L, ci);  /* in case of division by 0 */
         op_arithK(L, luaV_idiv, luai_numidiv);
         vmbreak;
       }
@@ -1412,6 +1440,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SHRI) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         int ic = GETARG_sC(i);
         lua_Integer ib;
@@ -1421,6 +1450,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_SHLI) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         int ic = GETARG_sC(i);
         lua_Integer ib;
@@ -1442,6 +1472,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_MOD) {
+        savestate(L, ci);  /* in case of division by 0 */
         op_arith(L, luaV_mod, luaV_modf);
         vmbreak;
       }
@@ -1454,6 +1485,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_IDIV) {  /* floor division */
+        savestate(L, ci);  /* in case of division by 0 */
         op_arith(L, luaV_idiv, luai_numidiv);
         vmbreak;
       }
@@ -1478,6 +1510,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_MMBIN) {
+        StkId ra = RA(i);
         Instruction pi = *(pc - 2);  /* original arith. expression */
         TValue *rb = vRB(i);
         TMS tm = (TMS)GETARG_C(i);
@@ -1487,6 +1520,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_MMBINI) {
+        StkId ra = RA(i);
         Instruction pi = *(pc - 2);  /* original arith. expression */
         int imm = GETARG_sB(i);
         TMS tm = (TMS)GETARG_C(i);
@@ -1496,6 +1530,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_MMBINK) {
+        StkId ra = RA(i);
         Instruction pi = *(pc - 2);  /* original arith. expression */
         TValue *imm = KB(i);
         TMS tm = (TMS)GETARG_C(i);
@@ -1505,6 +1540,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_UNM) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         lua_Number nb;
         if (ttisinteger(rb)) {
@@ -1519,6 +1555,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_BNOT) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         lua_Integer ib;
         if (tointegerns(rb, &ib)) {
@@ -1529,6 +1566,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_NOT) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         if (l_isfalse(rb))
           setbtvalue(s2v(ra));
@@ -1537,21 +1575,25 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_LEN) {
+        StkId ra = RA(i);
         Protect(luaV_objlen(L, ra, vRB(i)));
         vmbreak;
       }
       vmcase(OP_CONCAT) {
+        StkId ra = RA(i);
         int n = GETARG_B(i);  /* number of elements to concatenate */
-        L->top = ra + n;  /* mark the end of concat operands */
+        L->top.p = ra + n;  /* mark the end of concat operands */
         ProtectNT(luaV_concat(L, n));
-        checkGC(L, L->top); /* 'luaV_concat' ensures correct top */
+        checkGC(L, L->top.p); /* 'luaV_concat' ensures correct top */
         vmbreak;
       }
       vmcase(OP_CLOSE) {
+        StkId ra = RA(i);
         Protect(luaF_close(L, ra, LUA_OK, 1));
         vmbreak;
       }
       vmcase(OP_TBC) {
+        StkId ra = RA(i);
         /* create new to-be-closed upvalue */
         halfProtect(luaF_newtbcupval(L, ra));
         vmbreak;
@@ -1561,6 +1603,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_EQ) {
+        StkId ra = RA(i);
         int cond;
         TValue *rb = vRB(i);
         Protect(cond = luaV_equalobj(L, s2v(ra), rb));
@@ -1576,6 +1619,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_EQK) {
+        StkId ra = RA(i);
         TValue *rb = KB(i);
         /* basic types do not use '__eq'; we can use raw equality */
         int cond = luaV_rawequalobj(s2v(ra), rb);
@@ -1583,6 +1627,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_EQI) {
+        StkId ra = RA(i);
         int cond;
         int im = GETARG_sB(i);
         if (ttisinteger(s2v(ra)))
@@ -1611,11 +1656,13 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_TEST) {
+        StkId ra = RA(i);
         int cond = !l_isfalse(s2v(ra));
         docondjump();
         vmbreak;
       }
       vmcase(OP_TESTSET) {
+        StkId ra = RA(i);
         TValue *rb = vRB(i);
         if (l_isfalse(rb) == GETARG_k(i))
           pc++;
@@ -1626,11 +1673,12 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_CALL) {
+        StkId ra = RA(i);
         CallInfo *newci;
         int b = GETARG_B(i);
         int nresults = GETARG_C(i) - 1;
         if (b != 0)  /* fixed number of arguments? */
-          L->top = ra + b;  /* top signals number of arguments */
+          L->top.p = ra + b;  /* top signals number of arguments */
         /* else previous instruction set top */
         savepc(L);  /* in case of errors */
         if ((newci = luaD_precall(L, ra, nresults)) == NULL)
@@ -1642,54 +1690,57 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_TAILCALL) {
+        StkId ra = RA(i);
         int b = GETARG_B(i);  /* number of arguments + 1 (function) */
         int n;  /* number of results when calling a C function */
         int nparams1 = GETARG_C(i);
         /* delta is virtual 'func' - real 'func' (vararg functions) */
         int delta = (nparams1) ? ci->u.l.nextraargs + nparams1 : 0;
         if (b != 0)
-          L->top = ra + b;
+          L->top.p = ra + b;
         else  /* previous instruction set top */
-          b = cast_int(L->top - ra);
+          b = cast_int(L->top.p - ra);
         savepc(ci);  /* several calls here can raise errors */
         if (TESTARG_k(i)) {
           luaF_closeupval(L, base);  /* close upvalues from current call */
-          lua_assert(L->tbclist < base);  /* no pending tbc variables */
-          lua_assert(base == ci->func + 1);
+          lua_assert(L->tbclist.p < base);  /* no pending tbc variables */
+          lua_assert(base == ci->func.p + 1);
         }
         if ((n = luaD_pretailcall(L, ci, ra, b, delta)) < 0)  /* Lua function? */
           goto startfunc;  /* execute the callee */
         else {  /* C function? */
-          ci->func -= delta;  /* restore 'func' (if vararg) */
+          ci->func.p -= delta;  /* restore 'func' (if vararg) */
           luaD_poscall(L, ci, n);  /* finish caller */
           updatetrap(ci);  /* 'luaD_poscall' can change hooks */
           goto ret;  /* caller returns after the tail call */
         }
       }
       vmcase(OP_RETURN) {
+        StkId ra = RA(i);
         int n = GETARG_B(i) - 1;  /* number of results */
         int nparams1 = GETARG_C(i);
         if (n < 0)  /* not fixed? */
-          n = cast_int(L->top - ra);  /* get what is available */
+          n = cast_int(L->top.p - ra);  /* get what is available */
         savepc(ci);
         if (TESTARG_k(i)) {  /* may there be open upvalues? */
           ci->u2.nres = n;  /* save number of returns */
-          if (L->top < ci->top)
-            L->top = ci->top;
+          if (L->top.p < ci->top.p)
+            L->top.p = ci->top.p;
           luaF_close(L, base, CLOSEKTOP, 1);
           updatetrap(ci);
           updatestack(ci);
         }
         if (nparams1)  /* vararg function? */
-          ci->func -= ci->u.l.nextraargs + nparams1;
-        L->top = ra + n;  /* set call for 'luaD_poscall' */
+          ci->func.p -= ci->u.l.nextraargs + nparams1;
+        L->top.p = ra + n;  /* set call for 'luaD_poscall' */
         luaD_poscall(L, ci, n);
         updatetrap(ci);  /* 'luaD_poscall' can change hooks */
         goto ret;
       }
       vmcase(OP_RETURN0) {
         if (l_unlikely(L->hookmask)) {
-          L->top = ra;
+          StkId ra = RA(i);
+          L->top.p = ra;
           savepc(ci);
           luaD_poscall(L, ci, 0);  /* no hurry... */
           trap = 1;
@@ -1697,15 +1748,16 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         else {  /* do the 'poscall' here */
           int nres;
           L->ci = ci->previous;  /* back to caller */
-          L->top = base - 1;
+          L->top.p = base - 1;
           for (nres = ci->nresults; l_unlikely(nres > 0); nres--)
-            setnilvalue(s2v(L->top++));  /* all results are nil */
+            setnilvalue(s2v(L->top.p++));  /* all results are nil */
         }
         goto ret;
       }
       vmcase(OP_RETURN1) {
         if (l_unlikely(L->hookmask)) {
-          L->top = ra + 1;
+          StkId ra = RA(i);
+          L->top.p = ra + 1;
           savepc(ci);
           luaD_poscall(L, ci, 1);  /* no hurry... */
           trap = 1;
@@ -1714,12 +1766,13 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           int nres = ci->nresults;
           L->ci = ci->previous;  /* back to caller */
           if (nres == 0)
-            L->top = base - 1;  /* asked for no results */
+            L->top.p = base - 1;  /* asked for no results */
           else {
+            StkId ra = RA(i);
             setobjs2s(L, base - 1, ra);  /* at least this result */
-            L->top = base;
+            L->top.p = base;
             for (; l_unlikely(nres > 1); nres--)
-              setnilvalue(s2v(L->top++));  /* complete missing results */
+              setnilvalue(s2v(L->top.p++));  /* complete missing results */
           }
         }
        ret:  /* return from a Lua function */
@@ -1731,6 +1784,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         }
       }
       vmcase(OP_FORLOOP) {
+        StkId ra = RA(i);
         if (ttisinteger(s2v(ra + 2))) {  /* integer loop? */
           lua_Unsigned count = l_castS2U(ivalue(s2v(ra + 1)));
           if (count > 0) {  /* still more iterations? */
@@ -1749,12 +1803,14 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_FORPREP) {
+        StkId ra = RA(i);
         savestate(L, ci);  /* in case of errors */
         if (forprep(L, ra))
           pc += GETARG_Bx(i) + 1;  /* skip the loop */
         vmbreak;
       }
       vmcase(OP_TFORPREP) {
+       StkId ra = RA(i);
         /* create to-be-closed upvalue (if needed) */
         halfProtect(luaF_newtbcupval(L, ra + 3));
         pc += GETARG_Bx(i);
@@ -1763,7 +1819,8 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         goto l_tforcall;
       }
       vmcase(OP_TFORCALL) {
-       l_tforcall:
+       l_tforcall: {
+        StkId ra = RA(i);
         /* 'ra' has the iterator function, 'ra + 1' has the state,
            'ra + 2' has the control variable, and 'ra + 3' has the
            to-be-closed variable. The call will use the stack after
@@ -1771,29 +1828,31 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         */
         /* push function, state, and control variable */
         memcpy(ra + 4, ra, 3 * sizeof(*ra));
-        L->top = ra + 4 + 3;
+        L->top.p = ra + 4 + 3;
         ProtectNT(luaD_call(L, ra + 4, GETARG_C(i)));  /* do the call */
         updatestack(ci);  /* stack may have changed */
         i = *(pc++);  /* go to next instruction */
         lua_assert(GET_OPCODE(i) == OP_TFORLOOP && ra == RA(i));
         goto l_tforloop;
-      }
+      }}
       vmcase(OP_TFORLOOP) {
-        l_tforloop:
+       l_tforloop: {
+        StkId ra = RA(i);
         if (!ttisnil(s2v(ra + 4))) {  /* continue loop? */
           setobjs2s(L, ra + 2, ra + 4);  /* save control variable */
           pc -= GETARG_Bx(i);  /* jump back */
         }
         vmbreak;
-      }
+      }}
       vmcase(OP_SETLIST) {
+        StkId ra = RA(i);
         int n = GETARG_B(i);
         unsigned int last = GETARG_C(i);
         Table *h = hvalue(s2v(ra));
         if (n == 0)
-          n = cast_int(L->top - ra) - 1;  /* get up to the top */
+          n = cast_int(L->top.p - ra) - 1;  /* get up to the top */
         else
-          L->top = ci->top;  /* correct top in case of emergency GC */
+          L->top.p = ci->top.p;  /* correct top in case of emergency GC */
         last += n;
         if (TESTARG_k(i)) {
           last += GETARG_Ax(*pc) * (MAXARG_C + 1);
@@ -1810,12 +1869,14 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         vmbreak;
       }
       vmcase(OP_CLOSURE) {
+        StkId ra = RA(i);
         Proto *p = cl->p->p[GETARG_Bx(i)];
         halfProtect(pushclosure(L, p, cl->upvals, base, ra));
         checkGC(L, ra + 1);
         vmbreak;
       }
       vmcase(OP_VARARG) {
+        StkId ra = RA(i);
         int n = GETARG_C(i) - 1;  /* required results */
         Protect(luaT_getvarargs(L, ci, ra, n));
         vmbreak;
diff --git a/src/lvm.h b/src/lvm.h
index 1bc16f3a50ba..dba1ad277025 100644
--- a/src/lvm.h
+++ b/src/lvm.h
@@ -110,6 +110,11 @@ typedef enum {
       luaC_barrierback(L, gcvalue(t), v); }
 
 
+/*
+** Shift right is the same as shift left with a negative 'y'
+*/
+#define luaV_shiftr(x,y)	luaV_shiftl(x,intop(-, 0, y))
+
 
 
 LUAI_FUNC int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2);