https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88991
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2019-08-28
Version|9.0 |8.0
Ever confirmed|0 |1
Known to fail| |8.3.0, 9.2.0
--- Comment #3 from Martin Sebor <msebor at gcc dot gnu.org> ---
The test case in comment #0 seems to wrong/incomplete and doesn't compile.
Below is a test case that compiles and shows that GCC 9 issues warnings for the
first and third function but misses the one in the middle.
$ cat pr88991.c && gcc -O2 -S -Wall pr88991.c
char a[0], *s;
void f (void)
{
__builtin_memcpy (a, s, __builtin_strlen (s) + 1); // warning (good)
}
void g (void)
{
unsigned n = __builtin_strlen (s) + 1; // missing warning
__builtin_memcpy (a, s, n); // same here
}
void h (void)
{
__builtin_strcpy (a, s); // warning (good)
}
pr88991.c: In function ‘f’:
pr88991.c:5:3: warning: ‘__builtin_memcpy’ forming offset [1,
9223372036854775806] is out of the bounds [0, 0] of object ‘a’ with type
‘char[]’ [-Warray-bounds]
5 | __builtin_memcpy (a, s, __builtin_strlen (s) + 1); // warning
(good)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pr88991.c:1:6: note: ‘a’ declared here
1 | char a[0], *s;
| ^
pr88991.c: In function ‘h’:
pr88991.c:16:3: warning: ‘__builtin_strcpy’ forming offset 1 is out of the
bounds [0, 0] of object ‘a’ with type ‘char[]’ [-Warray-bounds]
16 | __builtin_strcpy (a, s); // warning (good)
| ^~~~~~~~~~~~~~~~~~~~~~~
pr88991.c:1:6: note: ‘a’ declared here
1 | char a[0], *s;
| ^
With -Warray-bounds disabled, GCC 9 issues the following:
pr88991.c: In function ‘f’:
pr88991.c:5:3: warning: ‘__builtin_memcpy’ writing between 1 and
9223372036854775806 bytes into a region of size 0 overflows the destination
[-Wstringop-overflow=]
5 | __builtin_memcpy (a, s, __builtin_strlen (s) + 1);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pr88991.c: In function ‘h’:
pr88991.c:16:3: warning: ‘__builtin_strcpy’ writing 1 or more bytes into a
region of size 0 overflows the destination [-Wstringop-overflow=]
16 | __builtin_strcpy (a, s);
| ^~~~~~~~~~~~~~~~~~~~~~~
