https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87431
ensadc at mailnesia dot com changed:
What |Removed |Added
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CC| |ensadc at mailnesia dot com
--- Comment #7 from ensadc at mailnesia dot com ---
This "optimization" might be unsafe in the presence of throwing conversion
operator:
// https://wandbox.org/permlink/ADEIfSv120QMrKeS
#include <variant>
#include <cassert>
struct weird {
operator int() { throw 0; }
};
int main() {
std::variant<char, int> v;
try {
v.emplace<1>(weird{});
} catch (...) {
assert((v.index() == std::variant_npos) ==
(v.valueless_by_exception()));
}
}
Maybe we can fix the optimization by making `emplace` restore the original
value (or not destroy in the first place) when the optimization is present and
an exception is thrown.
