[Bug middle-end/79220] missing -Wstringop-overflow= on a memcpy overflow with a small power-of-2 size

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79220

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=83508

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
In GCC 8.0 the overflow is diagnosed in both functions.  In f() by
-Wstringop-overflow as before, and in both functions (perhaps surprisingly) by
the newly enhanced -Warray-bounds warning (r255755).  There is still no
-Wstringop-overflow for g() so the limitation hasn't really been removed yet
and this bug should stay open until it is, and until the overflow in g() is
diagnosed -Wstringop-overflow when -Warray-bounds is disabled.

As an aside, the -Wstringop-overflow for f() will disappear if/when the patch
submitted for bug 83508 is committed.

pr79220.c: In function ‘g’:
pr79220.c:12:3: warning: ‘memcpy’ forming offset [4, 8] is out of the bounds
[0, 3] of object ‘d’ with type ‘char[3]’ [-Warray-bounds]
   memcpy (d, s, 8);
   ^~~~~~~~~~~~~~~~
pr79220.c:3:6: note: ‘d’ declared here
 char d[3];
      ^
pr79220.c: In function ‘f’:
pr79220.c:7:3: warning: ‘memcpy’ forming offset [4, 8] is out of the bounds [0,
3] of object ‘d’ with type ‘char[3]’ [-Warray-bounds]
   memcpy (d, "0123456789", 8);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
pr79220.c:3:6: note: ‘d’ declared here
 char d[3];
      ^
pr79220.c:7:3: warning: ‘memcpy’ writing 8 bytes into a region of size 3
overflows the destination [-Wstringop-overflow=]
   memcpy (d, "0123456789", 8);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~