Boost.Function and <boost/bind/apply.hpp>

[gast128]

Recently updated to Boost 1.86 and VS2022 (x64) and we get a weird compilation error:

#include <boost/bind/apply.hpp>  // comment this out to get success
#include <boost/bind/bind.hpp>
#include <boost/function.hpp>

int TestArg(int, double)
{
   return 0;
}


void f()
{
   boost::function<int (int)> fn = boost::bind(&TestArg, boost::placeholders::_1, 1.0);
}

Error:

1>D:\Work Sdk\boost_1_86_0\boost\function\function_template.hpp(926,35): error C2977: 'boost::apply': too many template arguments
1>(compiling source file 'Boost.cpp')
1> D:\Work Sdk\boost_1_86_0\boost\bind\apply.hpp(17,26):
1> see declaration of 'boost::apply'
1> D:\Work Sdk\boost_1_86_0\boost\function\function_template.hpp(926,35):
1> the template instantiation context (the oldest one first) is
1> D:\Work\Src\Temp\Bla\Boost.cpp(13,34):
1> see reference to function template instantiation 'boost::function<int (int)>::function<boost::_bi::bind_t<int,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>>(Functor,int)' being compiled
1> with
1> [
1> T=double,
1> Functor=boost::_bi::bind_t<int,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>
1> ]
1> D:\Work\Src\Temp\Bla\Boost.cpp(13,34):
1> see the first reference to 'boost::function<int (int)>::function' in 'f'
1> D:\Work Sdk\boost_1_86_0\boost\function\function_template.hpp(1084,24):
1> see reference to function template instantiation 'boost::function_n<R,int>::function_n<boost::_bi::bind_t<R,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>>(Functor,int)' being compiled
1> with
1> [
1> R=int,
1> T=double,
1> Functor=boost::_bi::bind_t<int,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>
1> ]
1> D:\Work Sdk\boost_1_86_0\boost\function\function_template.hpp(757,13):
1> see reference to function template instantiation 'void boost::function_n<R,int>::assign_to<boost::_bi::bind_t<R,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>>(Functor)' being compiled
1> with
1> [
1> R=int,
1> T=double,
1> Functor=boost::_bi::bind_t<int,int (__cdecl *)(int,double),boost::_bi::list<boost::arg<1>,boost::_bi::value>>
1> ]

If one comments out the <boost/bind/apply.hpp>it compiles fine. Using auto or std::function also works.

[pdimov]

That's a pretty annoying bug in MSVC; I thought it was no longer an issue in newer versions / later standard modes / /permissive-, but it looks like none of these affect this particular instance of it. :-/

You should report this to MS as a bug; in the meantime I'll try to figure out a way to avoid hitting it.

[pdimov]

I could think of nothing better than renaming the nested apply class template to avoid the conflict (which by the way only happens on msvc-14.3 / VS2022 with /permissive-, not on earlier compiler versions.)

[gast128]

Thx. I am a bit reluctant to enter a bug reports since MS has quite the habit with closing them as not reproducible,; not important or not our fault. I tried to reproduce it in compiler explorer but it seems that you cannot use external libraries for the MSVC compiler (it works when using GCC).