Use flexmembers on IBM XL C for AIX

This removes a workaround where Emacs did not use flexible
array members when compiled with IBM XL C.  Instead, avoid
the problem by making the aliasing issues more obvious to
this compiler.
* admin/merge-gnulib: Don’t remove m4/flexmember.m4.
* m4/flexmember.m4: Copy from gnulib.
* configure.ac (AC_C_FLEXIBLE_ARRAY_MEMBER): Remove workaround.
* src/alloc.c (allocate_string_data): Rephrase to avoid aliasing
problem that would otherwise mess up code generated for flexible
array members by IBM XL C for AIX, V12.1.
* src/conf_post.h (FLEXIBLE_ARRAY_MEMBER): Remove; now done
by gnulib code.

1 files changed, 0 insertions, 10 deletions

diff --git a/src/conf_post.h b/src/conf_post.h
index 865d0183a57..6d54524b970 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -358,16 +358,6 @@ extern int emacs_setenv_TZ (char const *);
 #define INLINE_HEADER_BEGIN _GL_INLINE_HEADER_BEGIN
 #define INLINE_HEADER_END _GL_INLINE_HEADER_END
 
-/* To use the struct hack with N elements, declare the struct like this:
-     struct s { ...; t name[FLEXIBLE_ARRAY_MEMBER]; };
-   and allocate (offsetof (struct s, name) + N * sizeof (t)) bytes.
-   IBM xlc 12.1 claims to do C99 but mishandles flexible array members.  */
-#ifdef __IBMC__
-# define FLEXIBLE_ARRAY_MEMBER 1
-#else
-# define FLEXIBLE_ARRAY_MEMBER
-#endif
-
 /* 'int x UNINIT;' is equivalent to 'int x;', except it cajoles GCC
    into not warning incorrectly about use of an uninitialized variable.  */
 #if defined GCC_LINT || defined lint