[committed] libstdc++: Use __is_single_threaded in locale initialization
Commit Message
Tested x86_64-linux, pushed to trunk.
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.
---
libstdc++-v3/src/c++98/locale_init.cc | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
@@ -31,6 +31,7 @@
#include <cctype>
#include <cwctype> // For towupper, etc.
#include <locale>
+#include <ext/atomicity.h>
#include <ext/concurrence.h>
#if _GLIBCXX_USE_DUAL_ABI
@@ -321,6 +322,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
void
locale::_S_initialize_once() throw()
{
+ // Need to check this because we could get called once from _S_initialize()
+ // when the program is single-threaded, and then again (via __gthread_once)
+ // when it's multi-threaded.
+ if (_S_classic)
+ return;
+
// 2 references.
// One reference for _S_classic, one for _S_global
_S_classic = new (&c_locale_impl) _Impl(2);
@@ -332,10 +339,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
locale::_S_initialize()
{
#ifdef __GTHREADS
- if (__gthread_active_p())
+ if (!__gnu_cxx::__is_single_threaded())
__gthread_once(&_S_once, _S_initialize_once);
#endif
- if (!_S_classic)
+ if (__builtin_expect(!_S_classic, 0))
_S_initialize_once();
}