Ah...ok I had to pass: -U_GNU_SOURCE to get things to build for a different reason. So let me check that out before you dig any further. Thanks, Rob ________________________________________ From: Boost <boost-bounces@lists.boost.org> on behalf of John Maddock <boost.regex@virgin.net> Sent: Monday, October 20, 2014 6:33 AM To: boost@lists.boost.org Subject: Re: [boost] [thread] linux.hpp, BOOST_HAS_PTHREAD_YIELD, BOOST_HAS_SCHED_YIELD
Reposting this here since I got no response on "users" but this list seems more appropriate:
Apologies for not replying before.
Using boost 1.55, Ubuntu 12.04, gcc 4.6
I'm building boost on linux using the lsb sdk (4.1.8) . I was getting the failure (paraphrased):
pthread_yield not declared
in libs/thread/src/thread.cpp 513
Weird. Fairly obviously that's a well tested combination, and normally both BOOST_HAS_PTHREAD_YIELD and BOOST_HAS_SCHED_YIELD will get defined. The former is a GNU extension, and I really should figure out what define triggers it's presence (_GNU_SOURCE probably, but I need to check). The latter is set in posix_features.hpp via: # if defined(_POSIX_PRIORITY_SCHEDULING) && (_POSIX_PRIORITY_SCHEDULING+0 > 0)\ || (defined(_POSIX_THREAD_PRIORITY_SCHEDULING) && (_POSIX_THREAD_PRIORITY_SCHEDULING+0 > 0))\ || (defined(_XOPEN_REALTIME) && (_XOPEN_REALTIME+0 >= 0)) # define BOOST_HAS_SCHED_YIELD # endif So for whatever reason, your version of <unistd.h> is not signalling the presence of this API. Indeed the linux man pages state: "POSIX systems on which sched_yield() is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>." which is clearly not the case here. I'll try and see what sched.h actually does on Linux. John.
The documentation for pthread_yield (http://man7.org/linux/man-pages/man3/pthread_yield.3.html) says:
This call is nonstandard, but present on several other systems. Use the standardized sched_yield(2)<http://man7.org/linux/man-pages/man2/sched_yield.2.html> instead.
If I change boost/config/platform/linux.hpp to define
BOOST_HAS_SCHED_YIELD
instead of
BOOST_HAS_PTHREAD_YIELD
Then sched_yield is used instead and the build finishes properly.
I'm posting this for two reasons:
1. To help others running into the same issue 2. To question whether linux.hpp should be updated officially as I did above 3. If not, why
Thanks,
Rob Conde
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