Boost C++ Libraries: Ticket #2240: Move placeholders into the boost::placeholders namespace

status changed

Peter Dimov — Thu, 21 Aug 2008 15:25:09 GMT

status new → assigned

milestone changed

Peter Dimov — Sat, 28 Feb 2009 17:02:18 GMT

milestone Boost 1.37.0 → To Be Determined

brwarner@… — Wed, 30 Jun 2010 18:03:53 GMT

I agree with this response, when using TR1 you can not use "using namespace std::placeholders" since it conflicts with the boost placeholders which are global.

status changed

Peter Dimov — Thu, 24 Feb 2011 22:09:24 GMT

status assigned → new

brwarner@… — Thu, 24 Feb 2011 22:20:37 GMT

What is the current status with this issue?

tliang — Fri, 09 Dec 2011 16:43:39 GMT

#including <boost/bind/placeholders.hpp> breaks code that uses the new std::placeholders.

cc set

Mon, 13 Aug 2012 00:01:33 GMT

cc flast@… added

cc changed

Wed, 12 Dec 2012 03:15:56 GMT

cc n.sakisaka@… added

+1, I think that it is highly important to fit the new spec of C++11.

version changed

Wed, 12 Dec 2012 03:17:16 GMT

version Boost 1.36.0 → Boost Development Trunk

anonymous — Mon, 17 Dec 2012 14:58:29 GMT

+1 They are actually worse than global, they are in an unnamed namespace, so even bringing the std::placeholders to the local workspace doesn't work. The only sensible workaround is to overload std::is_placeholder so that it works with boost placeholders, then use boost::placeholders everywhere. Do you think we could have this overload in boost itself? The following works great:

namespace std {
template<int n> struct is_placeholder<boost::arg<n>> : public integral_constant<int,n> {};
template<int n> struct is_placeholder<const boost::arg<n>> : public integral_constant<int,n> {};
/*namespace std*/ }

bret.kuhns — Wed, 29 Jan 2014 16:41:46 GMT

+1 this is very frustrating and requires a lot of disambiguation for something that should have always been in its own namespace to avoid these problems. Even better, argument-dependent lookup causes the boost placeholders in the inlined namespace to pull boost::bind as resolution candidate even though using namespace boost; never appears in my project (I do use the std namespace, however).

This is nasty, and confusing.