https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105294
Matthew House <mattlloydhouse at gmail dot com> changed:
What |Removed |Added
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CC| |mattlloydhouse at gmail dot com
--- Comment #2 from Matthew House <mattlloydhouse at gmail dot com> ---
Isn't this example invalid per the spec? At `*r = 42;`, `&*r` is based on `s`.
However, `*p = 13;` modifies the same object that `*r` refers to, and `&*p` is
not based on `s`, so the behavior is undefined.
I've recently found another example which is valid under the current spec as
well as the two new proposed definitions in N3025 and N3058.
https://godbolt.org/z/ezvMfPd78
static int x;
__attribute__ ((noinline))
int f(int * restrict p) {
*p = 1;
if (p == &x) {
*p = 2;
}
return *p;
}
int main(void) {
return f(&x);
}
At `*p = 2;`, `&*p` is based on `p` under every definition. However, both GCC
and Clang incorrectly assume that the write to `*p` inside the `if` block
cannot affect the return value.
