libstdc++: Use __is_single_threaded in locale initialization
This replaces a __gthread_active_p() check with __is_single_threaded() so that std::locale initialization doesn't use __gthread_once if it happens before the first thread is created. This means that _S_initialize_once() might now be called twice instead of only once, because if __is_single_threaded() changes to false then we will do the __gthread_once call even if _S_initialize_once() was already called. Add a check to _S_initialize_once() and return immediately if it is the second call. Also use __builtin_expect to _S_initialize, as the branch will be taken at most once in the lifetime of the program. libstdc++-v3/ChangeLog: * src/c++98/locale_init.cc (_S_initialize_once): Check if initialization has already been done. (_S_initialize): Replace __gthread_active_p with __is_single_threaded. Use __builtin_expect.
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@ -31,6 +31,7 @@
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#include <cctype>
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#include <cctype>
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#include <cwctype> // For towupper, etc.
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#include <cwctype> // For towupper, etc.
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#include <locale>
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#include <locale>
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#include <ext/atomicity.h>
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#include <ext/concurrence.h>
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#include <ext/concurrence.h>
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#if _GLIBCXX_USE_DUAL_ABI
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#if _GLIBCXX_USE_DUAL_ABI
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@ -321,6 +322,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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void
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void
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locale::_S_initialize_once() throw()
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locale::_S_initialize_once() throw()
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{
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{
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// Need to check this because we could get called once from _S_initialize()
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// when the program is single-threaded, and then again (via __gthread_once)
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// when it's multi-threaded.
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if (_S_classic)
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return;
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// 2 references.
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// 2 references.
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// One reference for _S_classic, one for _S_global
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// One reference for _S_classic, one for _S_global
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_S_classic = new (&c_locale_impl) _Impl(2);
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_S_classic = new (&c_locale_impl) _Impl(2);
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@ -332,10 +339,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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locale::_S_initialize()
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locale::_S_initialize()
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{
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{
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#ifdef __GTHREADS
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#ifdef __GTHREADS
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if (__gthread_active_p())
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if (!__gnu_cxx::__is_single_threaded())
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__gthread_once(&_S_once, _S_initialize_once);
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__gthread_once(&_S_once, _S_initialize_once);
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#endif
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#endif
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if (!_S_classic)
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if (__builtin_expect(!_S_classic, 0))
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_S_initialize_once();
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_S_initialize_once();
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}
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}
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