https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95279
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
There is nothing wrong on addition of -1, whether signed or cast to
size_t/uintptr_t, to a pointer, so if clang diagnoses that, it is buggy.
When the pointer points to start of some object, the addition of -1 can be
wrong, sure, but that isn't something in the testcase you've posted, there is
nothing to argue about it because you've used a constant, nor could be e.g. if
the pointer is initialized in some other function etc. That isn't something
the undefined behavior sanitizer can diagnose, for that something needs to
track the object boundaries at runtime (like e.g. -fsanitize=address does).
typedef __SIZE_TYPE__ size_t;
char *
foo (char *p)
{
size_t s = -1;
return p + s;
}
int
main ()
{
char buf[12] = "abcdefghijk";
char *p = foo (p + 1);
if (p != &buf[0])
__builtin_abort ();
return 0;
}
seems to confirm clang is buggy, or at least the sanitizer mode they are using
here checks something beyond what the standard requires, because this testcase
is just fine.
