1.54 regression: boost/thread/once.hpp includes boost/placeholders.hpp

[luto@…]

#include <functional>
#include <boost/thread/once.hpp>

using namespace std::placeholders;

static int x = sizeof(_1);

The code above compiles in C++11 mode on boost 1.53, but it fails on boost 1.54 like this:

boost_bind_bug.cpp:6:23: error: reference to ‘_1’ is ambiguous
 static int x = sizeof(_1);
                       ^
In file included from boost_bind_bug.cpp:1:0:
/usr/include/c++/4.8.2/functional:1004:34: note: candidates are: const std::_Placeholder<1> std::placeholders::_1
     extern const _Placeholder<1> _1;
                                  ^
In file included from /usr/include/boost/bind/bind.hpp:1742:0,
                 from /usr/include/boost/bind.hpp:22,
                 from /usr/include/boost/thread/pthread/once_atomic.hpp:19,
                 from /usr/include/boost/thread/once.hpp:20,
                 from boost_bind_bug.cpp:2:
/usr/include/boost/bind/placeholders.hpp:55:15: note:                 boost::arg<1> {anonymous}::_1
 boost::arg<1> _1;
               ^

This magic inclusion of boost/bind/placeholders.hpp is extremely impolite.

[viboes]

Well, Boost.Thread uses boost::bind, so I don't see where is the problem. The problem is that _1 is on the global namespace.

Moved to bind.