https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102221
--- Comment #2 from Giuseppe D'Angelo <dangelog at gmail dot com> ---
Hi,
Thanks for the analysis!
That basically allows me to reduce the testcase to something as simple as a
swap:
#include <memory>
#include <utility>
#if defined(SMART)
using ptr = std::unique_ptr<int>;
#else
using ptr = int *;
#endif
auto swap1(ptr &a, ptr &b) {
if (&a == &b)
__builtin_unreachable(); //
ptr tmp(std::move(a));
a = std::move(b);
b = std::move(tmp);
}
auto swap2(ptr &a, ptr &b)
{
// deliberate
std::swap<ptr>(a, b);
}
https://gcc.godbolt.org/z/Tqzz5eqrW
In both cases there's basically a call to "delete nullptr" that doesn't get
removed. I don't think this falls on libstdc++, rather than on the optimizer?
