Declared in <util/fs.h>
template<
class _ECharT,
class _Traits = char_traits<_ECharT>,
class _Allocator = allocator<_ECharT>>
[[nodiscard]]
basic_string<_ECharT, _Traits, _Allocator>
string(_Allocator const& __a = _Allocator()) const;
The return value should not be discarded.