OpenE2K/gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

libstdc++: Use __libc_single_threaded for locale initialization

Browse Source 
Most initialization of locales and facets happens before main() during
startup, when the program is likely to only have one thread. By using
the new __gnu_cxx::__is_single_threaded() function instead of checking
__gthread_active_p() we can avoid using pthread_once or atomics for the
common case.

That said, I'm not sure why we don't just use a local static variable
instead, as __cxa_guard_acquire() already optimizes for the
single-threaded case:

  static const bool init = (_S_initialize_once(), true);

I'll revisit that for GCC 12.

libstdc++-v3/ChangeLog:

	* src/c++98/locale.cc (locale::facet::_S_get_c_locale())
	(locale:🆔:_M_id() const): Use __is_single_threaded.
	* src/c++98/locale_init.cc (locale::_S_initialize()):
	Likewise.
This commit is contained in:
Jonathan Wakely 2020-11-24 12:29:30 +00:00
parent 97981e13b7
commit e253d36214
2 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
libstdc++-v3/src/c++98/locale.cc
View File

@ -214,7 +214,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
locale::facet::_S_get_c_locale() locale::facet::_S_get_c_locale()
{ {
#ifdef __GTHREADS #ifdef __GTHREADS
if (__gthread_active_p()) if (!__gnu_cxx::__is_single_threaded())
__gthread_once(&_S_once, _S_initialize_once); __gthread_once(&_S_once, _S_initialize_once);
else else
#endif #endif
@ -515,7 +515,7 @@ namespace {
#endif #endif
#ifdef __GTHREADS #ifdef __GTHREADS
if (__gthread_active_p()) if (!__gnu_cxx::__is_single_threaded())
{ {
if (__atomic_always_lock_free(sizeof(_M_index), &_M_index)) if (__atomic_always_lock_free(sizeof(_M_index), &_M_index))
{ {

2
libstdc++-v3/src/c++98/locale_init.cc
View File

@ -320,7 +320,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
locale::_S_initialize() locale::_S_initialize()
{ {
#ifdef __GTHREADS #ifdef __GTHREADS
if (__gthread_active_p()) if (!__gnu_cxx::__is_single_threaded())
__gthread_once(&_S_once, _S_initialize_once); __gthread_once(&_S_once, _S_initialize_once);
#endif #endif
if (!_S_classic) if (!_S_classic)