[Bug middle-end/92942] missing -Wstringop-overflow for allocations with a negative lower bound size

["msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92942

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
   Target Milestone|---                         |11.0
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=97342
             Status|ASSIGNED                    |RESOLVED

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
The patch referenced in comment #2 was never reviewed but the bug was resolved
by the improvements to compute_objsize() committed as part of the fix for
pr97342.  GCC 11 detects both buffer overflows:

$ gcc -O2 -S -Wall pr92942.c
pr92942.c: In function ‘f’:
pr92942.c:10:3: warning: ‘__builtin_memcpy’ writing 6 bytes into a region of
size between 0 and 3 [-Wstringop-overflow=]
   10 |   strcpy (p, "12345");   // buffer overflow detected
      |   ^~~~~~~~~~~~~~~~~~~
pr92942.c:9:13: note: at offset 0 to an object with size at most 3 allocated by
‘malloc’ here
    9 |   void *p = malloc (n);
      |             ^~~~~~~~~~
pr92942.c: In function ‘g’:
pr92942.c:20:3: warning: ‘__builtin_memcpy’ writing 6 bytes into a region of
size between 0 and 3 [-Wstringop-overflow=]
   20 |   strcpy (p, "12345");   // buffer overflow not detected
      |   ^~~~~~~~~~~~~~~~~~~
pr92942.c:19:13: note: at offset 0 to an object with size at most 3 allocated
by ‘malloc’ here
   19 |   void *p = malloc (n);
      |             ^~~~~~~~~~