https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111258
Bug ID: 111258
Summary: std::string cannot to be moved in constant evaluated
expression
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: kisses07_rupee at icloud dot com
Target Milestone: ---
c++20 std::string's destructor fails after move:
#include <string>
using namespace std::literals;
constexpr auto foo(auto a) {
auto b = std::move(a);
return b[1];
}
int main(int,char**) {
static_assert( foo("hello"s) == 'e' );
return 0;
}
fails with:
<source>: In function 'int main(int, char**)':
<source>:11:34: error: non-constant condition for static assertion
11 | static_assert( foo("hello"s) == 'e' );
| ~~~~~~~~~~~~~~^~~~~~
<source>:11:23: in 'constexpr' expansion of
'foo<std::__cxx11::basic_string<char>
>(std::literals::string_literals::operator""s(const char*, std::size_t)(5))'
<source>:11:42: in 'constexpr' expansion of
'std::__cxx11::basic_string<char>((* &
std::move<__cxx11::basic_string<char>&>(a)))'
<source>:11:34: error: accessing 'std::__cxx11::basic_string<char>::<unnamed
union>::_M_allocated_capacity' member instead of initialized
'std::__cxx11::basic_string<char>::<unnamed union>::_M_local_buf' member in
constant expression
Compiler returned: 1
online demo: https://godbolt.org/z/Tz7MK58f1
it seems it's affecting on bug 103924
