1 files changed, 69 insertions, 0 deletions
diff --git a/contrib/bmake/unit-tests/cond-undef-lint.mk b/contrib/bmake/unit-tests/cond-undef-lint.mk
new file mode 100755
index 000000000000..334ceb594054
--- /dev/null
+++ b/contrib/bmake/unit-tests/cond-undef-lint.mk
@@ -0,0 +1,69 @@
+# $NetBSD: cond-undef-lint.mk,v 1.2 2020/09/14 07:13:29 rillig Exp $
+#
+# Tests for defined and undefined variables in .if conditions, in lint mode.
+#
+# As of 2020-09-14, lint mode contains experimental code for printing
+# accurate error messages in case of undefined variables, instead of the
+# wrong "Malformed condition".
+#
+# See also:
+#	opt-debug-lint.mk
+
+.MAKEFLAGS: -dL
+
+# DEF is defined, UNDEF is not.
+DEF=		defined
+
+# An expression based on a defined variable is fine.
+.if !${DEF}
+.  error
+.endif
+
+# Since the condition fails to evaluate, neither of the branches is taken.
+.if ${UNDEF}
+.  error
+.else
+.  error
+.endif
+
+# The variable name depends on the undefined variable, which is probably a
+# mistake.  The variable UNDEF, as used here, can be easily turned into
+# an expression that is always defined, using the :U modifier.
+#
+# The outer expression does not generate an error message since there was
+# already an error evaluating this variable's name.
+#
+# TODO: Suppress the error message "Variable VAR. is undefined".  That part
+# of the expression must not be evaluated at all.
+.if ${VAR.${UNDEF}}
+.  error
+.else
+.  error
+.endif
+
+# The variable VAR.defined is not defined and thus generates an error message.
+.if ${VAR.${DEF}}
+.  error
+.else
+.  error
+.endif
+
+
+# Variables that are referenced indirectly may be undefined in a condition.
+#
+# A practical example for this is CFLAGS, which consists of CWARNS, COPTS
+# and a few others.  Just because these nested variables are not defined,
+# this does not make the condition invalid.
+#
+# The crucial point is that at the point where the variable appears in the
+# condition, there is no way to influence the definedness of the nested
+# variables.  In particular, there is no modifier that would turn undefined
+# nested variables into empty strings, as an equivalent to the :U modifier.
+INDIRECT=	${NESTED_UNDEF} ${NESTED_DEF}
+NESTED_DEF=	nested-defined
+
+# Since NESTED_UNDEF is not controllable at this point, it must not generate
+# an error message, and it doesn't do so, since 2020-09-14.
+.if !${INDIRECT}
+.  error
+.endif