Date: Thu, 30 Jun 2016 15:15:47 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Subject: Re: Issues when building libcxx libcxxabi with MUSL * Julien Ramseier <j.ramseier@...il.com> [2016-06-30 14:50:14 +0200]: > > Le 22 juin 2016 à 21:41, Rich Felker <dalias@...c.org> a écrit : > > > > On Wed, Jun 22, 2016 at 09:38:17PM +0200, Julien Ramseier wrote: > >> Hi Zhao, > >> > >> Not sure how you did build llvm-libcxx, but the only issue I encountered myself is > >> the use of PTHREAD_MUTEX_INITIALIZER in libcxx include/__mutex_base. > >> musl uses volatile types in its pthread_mutex_t struct and C++11 does not allow them > >> with constexpr member initializers. This rule has been relaxed in C++14. > > > > Note that the code using them is still formally/conceptually buggy. > > POSIX does not permit using these initializers as values. They can > > only be used as initializers for objects with static storage duration. > > A "mutex value" makes no sense; mutexes are objects not values. > > Actually the latest POSIX spec allows it. > See http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_init.html <http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_mutex_init.html> > yes, the changelog says POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0460 [70,428] is applied. so the semantics changed in 2013 http://austingroupbugs.net/view.php?id=70 > A workaround for the C++11 constexpr issue should land soon in libcxx trunk. > http://reviews.llvm.org/D21637 <http://reviews.llvm.org/D21637> > note that without pthread_mutex_destroy it may leak resources. (in practice this e.g. matters on freebsd see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71684 on musl this is not an issue)
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