diff options
Diffstat (limited to 'contrib/llvm-project/libcxx/include/__config')
| -rw-r--r-- | contrib/llvm-project/libcxx/include/__config | 56 |
1 files changed, 36 insertions, 20 deletions
diff --git a/contrib/llvm-project/libcxx/include/__config b/contrib/llvm-project/libcxx/include/__config index e4b7d25edf34..22c2ed7fd87b 100644 --- a/contrib/llvm-project/libcxx/include/__config +++ b/contrib/llvm-project/libcxx/include/__config @@ -26,6 +26,13 @@ # define _LIBCPP_VERSION 15000 +# define _LIBCPP_CONCAT_IMPL(_X, _Y) _X##_Y +# define _LIBCPP_CONCAT(_X, _Y) _LIBCPP_CONCAT_IMPL(_X, _Y) + +// Valid C++ identifier that revs with every libc++ version. This can be used to +// generate identifiers that must be unique for every released libc++ version. +# define _LIBCPP_VERSIONED_IDENTIFIER _LIBCPP_CONCAT(v, _LIBCPP_VERSION) + # if __STDC_HOSTED__ == 0 # define _LIBCPP_FREESTANDING # endif @@ -568,12 +575,6 @@ typedef __char32_t char32_t; # endif // defined(_LIBCPP_OBJECT_FORMAT_COFF) -# if __has_attribute(internal_linkage) -# define _LIBCPP_INTERNAL_LINKAGE __attribute__((internal_linkage)) -# else -# define _LIBCPP_INTERNAL_LINKAGE _LIBCPP_ALWAYS_INLINE -# endif - # if __has_attribute(exclude_from_explicit_instantiation) # define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION __attribute__((__exclude_from_explicit_instantiation__)) # else @@ -583,20 +584,35 @@ typedef __char32_t char32_t; # define _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION _LIBCPP_ALWAYS_INLINE # endif -# ifndef _LIBCPP_HIDE_FROM_ABI_PER_TU -# ifndef _LIBCPP_HIDE_FROM_ABI_PER_TU_BY_DEFAULT -# define _LIBCPP_HIDE_FROM_ABI_PER_TU 0 -# else -# define _LIBCPP_HIDE_FROM_ABI_PER_TU 1 -# endif -# endif - -# ifndef _LIBCPP_HIDE_FROM_ABI -# if _LIBCPP_HIDE_FROM_ABI_PER_TU -# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_INTERNAL_LINKAGE -# else -# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION -# endif +// This macro marks a symbol as being hidden from libc++'s ABI. This is achieved +// on two levels: +// 1. The symbol is given hidden visibility, which ensures that users won't start exporting +// symbols from their dynamic library by means of using the libc++ headers. This ensures +// that those symbols stay private to the dynamic library in which it is defined. +// +// 2. The symbol is given an ABI tag that changes with each version of libc++. This ensures +// that no ODR violation can arise from mixing two TUs compiled with different versions +// of libc++ where we would have changed the definition of a symbol. If the symbols shared +// the same name, the ODR would require that their definitions be token-by-token equivalent, +// which basically prevents us from being able to make any change to any function in our +// headers. Using this ABI tag ensures that the symbol name is "bumped" artificially at +// each release, which lets us change the definition of these symbols at our leisure. +// Note that historically, this has been achieved in various ways, including force-inlining +// all functions or giving internal linkage to all functions. Both these (previous) solutions +// suffer from drawbacks that lead notably to code bloat. +// +// Note that we use _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION to ensure that we don't depend +// on _LIBCPP_HIDE_FROM_ABI methods of classes explicitly instantiated in the dynamic library. +// +// TODO: We provide a escape hatch with _LIBCPP_NO_ABI_TAG for folks who want to avoid increasing +// the length of symbols with an ABI tag. In practice, we should remove the escape hatch and +// use compression mangling instead, see https://github.com/itanium-cxx-abi/cxx-abi/issues/70. +# ifndef _LIBCPP_NO_ABI_TAG +# define _LIBCPP_HIDE_FROM_ABI \ + _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION \ + __attribute__((__abi_tag__(_LIBCPP_TOSTRING(_LIBCPP_VERSIONED_IDENTIFIER)))) +# else +# define _LIBCPP_HIDE_FROM_ABI _LIBCPP_HIDDEN _LIBCPP_EXCLUDE_FROM_EXPLICIT_INSTANTIATION # endif # ifdef _LIBCPP_BUILDING_LIBRARY |