https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94498
Bug ID: 94498
Summary: std::basic_string_view::copy not qualified constexpr
in c++2a
Product: gcc
Version: 9.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: takechi101010 at gmail dot com
Target Milestone: ---
Following code fails to compile:
```c++
#include <iostream>
#include <fstream>
#include <string_view>
constexpr size_t copy(std::string_view str, char* dst) {
return str.copy(dst, 1);
}
int main() {
std::string_view str = "aaaa";
char a[2];
copy(str, a);
std::cout << a[0] << std::endl;
}
```
with:
```
prog.cc: In function 'constexpr size_t copy(std::string_view, char*)':
prog.cc:6:20: error: call to non-'constexpr' function
'std::basic_string_view<_CharT, _Traits>::size_type
std::basic_string_view<_CharT, _Traits>::copy(_CharT*,
std::basic_string_view<_CharT, _Traits>::size_type,
std::basic_string_view<_CharT, _Traits>::size_type) const [with _CharT = char;
_Traits = std::char_traits<char>; std::basic_string_view<_CharT,
_Traits>::size_type = long unsigned int]'
6 | return str.copy(dst, 1);
| ~~~~~~~~^~~~~~~~
```
https://wandbox.org/permlink/pNreqN8l5RPdPlTZ
