Boost C++ Libraries: Ticket #9848: flyweight: hidden dependency on pthread

Joaquín M López Muñoz — Mon, 07 Apr 2014 16:38:42 GMT

Hi,

The dependency stems from the usage of boost::flyweights::simple_locking:

http://www.boost.org/libs/flyweight/doc/reference/locking.html#simple_locking

which takes advantage of the synchronization mechanisms available on the target environment. Your ArchLinux GCC distribution is configured in such a way that BOOST_HAS_PTHREADS is defined hence the need to link Pthreads with -lpthread. If you don't want to do the linking because your app is single-thread, you can either

use boost::flyweights::no_locking as the locking policy or
globally set the BOOST_DISABLE_THREADS macro.

Please report back whether this clarifies the issue for you. Best,

status changed; resolution set

Joaquín M López Muñoz — Tue, 08 Apr 2014 10:06:50 GMT

status new → closed
resolution → invalid

akim@… — Tue, 08 Apr 2014 15:42:21 GMT

Hi Joaquin,

Thanks for the quick response.

Actually, I already use no_locking in my project. Here is a small example:

[forge@prague tmp]$ cat foo.cc
#include <boost/flyweight.hpp>
#include <boost/flyweight/no_tracking.hpp>
using string = boost::flyweight<std::string, boost::flyweights::no_tracking>;
int main()
{
  string h{"Hello, World!"};
}
[forge@prague tmp]$ clang++-3.4 -std=c++11 foo.cc
/tmp/foo-856a4c.o:foo.cc:function boost::flyweights::detail::recursive_lightweight_mutex::recursive_lightweight_mutex(): error: undefined reference to 'pthread_mutexattr_init'
/tmp/foo-856a4c.o:foo.cc:function boost::flyweights::detail::recursive_lightweight_mutex::recursive_lightweight_mutex(): error: undefined reference to 'pthread_mutexattr_settype'
/tmp/foo-856a4c.o:foo.cc:function boost::flyweights::detail::recursive_lightweight_mutex::recursive_lightweight_mutex(): error: undefined reference to 'pthread_mutexattr_destroy'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Sure, it works with BOOST_DISABLE_THREADS, but then again, I have seen nothing about this in the documentation. A section on the dependencies would be helpful imho.

Joaquín M López Muñoz — Tue, 08 Apr 2014 20:47:47 GMT

You're using no_tracking, not no_locking.

Wed, 09 Apr 2014 13:50:23 GMT

Bwahaha! Thanks for pointing this out...

(But still, don't you think dependencies such as pthreads etc. should be mentioned in the documentation?)

status changed; resolution deleted

Joaquín M López Muñoz — Thu, 10 Apr 2014 18:56:12 GMT

status closed → reopened
resolution invalid

status changed; resolution set

Joaquín M López Muñoz — Thu, 10 Apr 2014 18:56:29 GMT

status reopened → closed
resolution → fixed

Added note on Pthreads dependency, see

https://github.com/boostorg/flyweight/commit/1ea709b6249cca1b7af33feed20d855c2d72542c

akim@… — Fri, 11 Apr 2014 06:57:31 GMT

Great! Thanks a lot for Flyweights!