On Thu, 21 Sep 2023 21:06:59 +0200 Christian Franke wrote: > Brian Inglis via Cygwin wrote: > > On 2023-09-21 10:28, Takashi Yano via Cygwin wrote: > >> On Fri, 22 Sep 2023 01:12:04 +0900 > >> Takashi Yano wrote: > >>> I wonder why the following code throws std::runtime_error > >>> even though the LC_ALL is set to valid locale other than "C". > >>> This does not occur only when LC_ALL is set to "C". > >>> > >>> #include <locale> > >>> int main() > >>> { > >>> std::locale(""); > >>> return 0; > >>> } > >>> > >>> In linux, this occurs only when the LC_ALL is set to invalid > >>> locale (i.e. locale that is not registered in system). > >> > >> Similarly, > >> std::locale("ja_JP.UTF-8") > >> throws std::runtime_error in cygwin. > > > > Looks like the implementation does not like any default "" or explicit > > "en_US.UTF-8" strings there! See example at link and below; results > > are always the same: > > > > https://en.cppreference.com/w/cpp/locale/locale > > > > #include <iostream> > > #include <locale> > > > > int main() > > { > > std::wcout << "User-preferred locale setting is " > > << std::locale().name().c_str() << '\n'; > > > > // on startup, the global locale is the "C" locale > > std::wcout << 1000.01 << '\n'; > > > > // replace the C++ global locale and the "C" locale with the > > user-preferred locale > > std::locale::global(std::locale("")); > > // use the new global locale for future wide character output > > std::wcout.imbue(std::locale()); > > > > // output the same number again > > std::wcout << 1000.01 << '\n'; > > } > > > > $ g++ -o c++locale{,.cc} > > $ ./c++locale > > User-preferred locale setting is C > > 1000.01 > > terminate called after throwing an instance of 'std::runtime_error' > > what(): locale::facet::_S_create_c_locale name not valid > > Aborted (core dumped) > > > > According to libstdc++ source, the internal function > locale::facet::_S_create_c_locale() calls some __newlocale() which > apparently does not arrive at newlocale() from cygwin1.dll. But > cygstdc++-6.dll imports newlocale() from cygwin1.dll.
Thanks for the pointer. I looked into the cygstdc++6.dll source code, and noticed that the code you mentioned is for glibc. In glibc, __newlocale() is defined and newlocale() is a weak alias for that. For generic libc (i.e. other than glibc), _S_create_c_locale() is defined as: void locale::facet::_S_create_c_locale(__c_locale& __cloc, const char* __s, __c_locale) { // Currently, the generic model only supports the "C" locale. // See http://gcc.gnu.org/ml/libstdc++/2003-02/msg00345.html __cloc = 0; if (strcmp(__s, "C")) __throw_runtime_error(__N("locale::facet::_S_create_c_locale " "name not valid")); } in /libstdc++-v3/config/locale/generic/c_locale.cc. Obviously from the code, locale other than "C" causes runtime_error. The behaviour is as designed but not a bug in cygwin environment. Thanks for discussion. -- Takashi Yano <takashi.y...@nifty.ne.jp> -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple