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, 6 insertions, 5 deletions

diff --git a/lib-src/ebrowse.c b/lib-src/ebrowse.c
index c59181f9464..7a262005df9 100644
--- a/lib-src/ebrowse.c
+++ b/lib-src/ebrowse.c
@@ -32,6 +32,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #define SEEK_END 2
 #endif
 
+#include <flexmember.h>
 #include <min-max.h>
 
 /* Files are read in chunks of this number of bytes.  */
@@ -582,7 +583,7 @@ add_sym (const char *name, struct sym *nested_in_class)
           puts (name);
         }
 
-      sym = xmalloc (offsetof (struct sym, name) + strlen (name) + 1);
+      sym = xmalloc (FLEXSIZEOF (struct sym, name, strlen (name) + 1));
       memset (sym, 0, offsetof (struct sym, name));
       strcpy (sym->name, name);
       sym->namesp = scope;
@@ -867,8 +868,8 @@ add_global_decl (char *name, char *regexp, int pos, unsigned int hash, int var,
 static struct member *
 add_member (struct sym *cls, char *name, int var, int sc, unsigned int hash)
 {
-  struct member *m = xmalloc (offsetof (struct member, name)
-                              + strlen (name) + 1);
+  struct member *m = xmalloc (FLEXSIZEOF (struct member, name,
+                                          strlen (name) + 1));
   struct member **list;
   struct member *p;
   struct member *prev;
@@ -978,7 +979,7 @@ mark_inherited_virtual (void)
 static struct sym *
 make_namespace (char *name, struct sym *context)
 {
-  struct sym *s = xmalloc (offsetof (struct sym, name) + strlen (name) + 1);
+  struct sym *s = xmalloc (FLEXSIZEOF (struct sym, name, strlen (name) + 1));
   memset (s, 0, offsetof (struct sym, name));
   strcpy (s->name, name);
   s->next = all_namespaces;
@@ -1062,7 +1063,7 @@ register_namespace_alias (char *new_name, struct link *old_name)
     if (streq (new_name, al->name) && (al->namesp == current_namespace))
       return;
 
-  al = xmalloc (offsetof (struct alias, name) + strlen (new_name) + 1);
+  al = xmalloc (FLEXSIZEOF (struct alias, name, strlen (new_name) + 1));
   strcpy (al->name, new_name);
   al->next = namespace_alias_table[h];
   al->namesp = current_namespace;