Port flexible array members to GCC + valgrind

These changes are needed to conform to the C standard's rule for
allocating structs containing flexible array members.  C11 says
that malloc (offsetof (struct s, m) + n) does not suffice to
allocate a struct with an n-byte tail; instead, malloc’s arg
should be rounded up to the nearest multiple of alignof (struct s).
Although this is arguably a defect in C11, gcc -O2 + valgrind
sometimes complains when this rule is violated, and when debugging
it’s better to keep valgrind happy.
For details please see the thread containing the message at:
https://gcc.gnu.org/ml/gcc-patches/2016-09/msg00416.html
* lib-src/ebrowse.c, src/alloc.c, src/image.c, src/process.c:
Include flexmember.h.
* lib-src/ebrowse.c (add_sym, add_member, make_namespace)
(register_namespace_alias):
* src/alloc.c (SDATA_SIZE, allocate_string_data):
* src/image.c (xpm_cache_color, imagemagick_create_cache):
* src/process.c (Fmake_network_process):
Use FLEXSIZEOF instead of offsetof and addition.
* src/alloc.c (SDATA_SIZE, vector_alignment):
Use FLEXALIGNOF instead of sizeof (ptrdiff_t).
* src/lisp.h (ALIGNOF_STRUCT_LISP_VECTOR):
Remove, as alloc.c can now calculate this on its own.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/image.c b/src/image.c
index 7a554ef1b63..f15c2788967 100644
--- a/src/image.c
+++ b/src/image.c
@@ -30,7 +30,9 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #endif
 
 #include <setjmp.h>
+
 #include <c-ctype.h>
+#include <flexmember.h>
 
 #include "lisp.h"
 #include "frame.h"
@@ -3347,7 +3349,7 @@ xpm_cache_color (struct frame *f, char *color_name, XColor *color, int bucket)
   if (bucket < 0)
     bucket = xpm_color_bucket (color_name);
 
-  nbytes = offsetof (struct xpm_cached_color, name) + strlen (color_name) + 1;
+  nbytes = FLEXSIZEOF (struct xpm_cached_color, name, strlen (color_name) + 1);
   p = xmalloc (nbytes);
   strcpy (p->name, color_name);
   p->color = *color;
@@ -8328,8 +8330,8 @@ static struct animation_cache *
 imagemagick_create_cache (char *signature)
 {
   struct animation_cache *cache
-    = xmalloc (offsetof (struct animation_cache, signature)
-               + strlen (signature) + 1);
+    = xmalloc (FLEXSIZEOF (struct animation_cache, signature,
+                           strlen (signature) + 1));
   cache->wand = 0;
   cache->index = 0;
   cache->next = 0;