On Monday 06 July 2015 at 14:51:42 +0100, Jonathan Wakely wrote: > On 06/07/15 13:55 +0100, Mike Crowe wrote: > >diff --git a/libgcc/gthr-posix.h b/libgcc/gthr-posix.h > >index fb59816..0e01866 100644 > >--- a/libgcc/gthr-posix.h > >+++ b/libgcc/gthr-posix.h > >@@ -33,6 +33,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > >If not, see > >#define __GTHREADS_CXX0X 1 > > > >#include <pthread.h> > >+#include <time.h> > > > >#if ((defined(_LIBOBJC) || defined(_LIBOBJC_WEAK)) \ > > || !defined(_GTHREAD_USE_MUTEX_TIMEDLOCK)) > >@@ -44,6 +45,11 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > >If not, see > ># endif > >#endif > > > >+ > >+#if defined(_GLIBCXX_USE_PTHREAD_COND_TIMEDWAITONCLOCK_NP) > >+# define _GTHREAD_USE_COND_TIMEDWAITONCLOCK 1 > >+#endif > > This isn't correct, because it's possible to include <gthr.h> before > including any C++ Standard Library header, so the _GLIBCXX_ macro > defined in libstdc++'s c++config.h will not have been defined.
Presumably gthr-posix.h could just include c++config.h to avoid that, but perhaps it's not that simple which is why gthr-posix.h swings through hoops to define _GTHREAD_USE_MUTEX_TIMEDLOCK itself? > It might make sense to just do this internally in libstdc++ and not > involve gthr-posix.h at all, this is what we do for pthread_rwlock_t > usage in <shared_mutex> so you might want to follow that model. I implemented the new function in gthreads because that seemed to be what https://gcc.gnu.org/bugzilla/show_bug.cgi?id=41861 was suggesting and I'd incorrectly assumed that there were non-pthreads backends for gthreads too. I'm can try and re-implement condition_variable using pthreads directly but the change will be somewhat larger and it would break non-pthreads platforms. > How portable is pthread_cond_timedwaitonclock_np? Is it unique to > glibc or do any other posix systems provide it? It's not at all portable; I invented it because it seemed to be the most straightforward way to correctly support std::condition_variable's wait operations using std::chrono::steady_clock on Linux. I haven't even suggested adding the function on the glibc mailing list yet. I looked briefly to see if I could find anyone else solving the problem on Posix platforms but they all seem to be converting to system_clock too. :( Thanks. Mike.
