https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118220
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |hubicka at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think we discussed replacing if (!p) with if (size > N) with some special N
but disregarded it with a reason I don't exactly remember.
Yes, the testcase invokes UB after the change, but it also relies on
behavior of glibc here (but of course the valid "glibc program" is no
longer valid after the change).
Consider an implementation that does
void *malloc (size_t) { return NULL; }
would
int test(void) {
char *const p = malloc(4);
if (!p) {
return 0;
}
int i = 1 / 0;
free(p);
return i;
}
be then invalid to optimize to eliding the malloc/free and the if (!p)
check? Alternatively the program might know memory is exhausted when calling
test(), and malloc () to always fail. But can the programmer really
rely on this?
So I'm not sure if this is really a bug.
There's a flag to disable the optimization.
