https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98725
Bug ID: 98725
Summary: Review what is disabled in libstdc++ by
--disable-wchar_t
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
Currently libstdc++ guards *any* use of wchar_t with a check for
_GLIBCXX_USE_WCHAR_T. This has unfortunate consequences such as
std::wstring_convert being unusable to convert between char and char16_t (which
doesn't use wchar_t at all). That's because we do this in <bits/locale_conv.h>:
#ifdef _GLIBCXX_USE_WCHAR_T
_GLIBCXX_BEGIN_NAMESPACE_CXX11
/// String conversions
template<typename _Codecvt, typename _Elem = wchar_t,
typename _Wide_alloc = allocator<_Elem>,
typename _Byte_alloc = allocator<char>>
class wstring_convert
The wchar_t type exists unconditionally for C++, so traits like
std::is_integral_v<wchar_t> are already always defined as true.
std::char_traits<wchar_t> also works, by using the primary template (which
works for any character-like type). That means that even std::wstring works,
albeit slower than if we had optimized support for <wchar.h> in libc.
The consequences of --disable-wchar_t (whether implicit or explicit) should to
disable explicit instantiations for std::wstring, std::wifstream etc. and to
disable wchar_t support in locales and std::filesystem. It doesn't need to
disable everything that refers to wchar_t.
