Boost C++ Libraries: Ticket #13007: When BOOST_BIND_NO_PLACEHOLDERS is defined, framework.ipp seems to be missing an #include

owner, status changed

Raffi Enficiaud — Tue, 06 Jun 2017 14:19:34 GMT

owner changed from Gennadiy Rozental to Raffi Enficiaud
status new → assigned

milestone changed

Raffi Enficiaud — Tue, 06 Jun 2017 14:19:46 GMT

milestone To Be Determined → Boost 1.65.0

Raffi Enficiaud — Fri, 23 Jun 2017 16:09:54 GMT

Sorry, I am not able to reproduce the error:

#define BOOST_BIND_NO_PLACEHOLDERS
#define BOOST_TEST_MODULE bind_no_placeholder
#include <boost/test/unit_test.hpp>
BOOST_AUTO_TEST_CASE(test1)
{
    int i = 1;
    BOOST_TEST(1 == i);
}

works. Am I missing something? I am doing this on the current develop branch.

bspencer@… — Fri, 23 Jun 2017 16:50:28 GMT

Sorry for not being specific enough originally.

I can reproduce it on boost-1.64.0 if I use the headers-only include in your test program.

#include <boost/test/included/unit_test.hpp

It also happens if you define BOOST_BIND_NO_PLACEHOLDERS in boost/config/user.hpp and compile the standalone Boost.Test library.

Raffi Enficiaud — Sat, 24 Jun 2017 19:23:09 GMT

Ok, thank you for the feedback. I am hesitating concerning the fix of forcing the include of the placeholders.hpp even if the macro is defined. OTOH, the fact that this is working in case of non-header-only variant is also not coherent.

What is the use case of the BOOST_BIND_NO_PLACEHOLDERS for you? I still do not understand why you would like to use this non-documented macro and what is the benefit. When you define it, do you include std:: placeholders instead?

bspencer@… — Fri, 07 Jul 2017 21:21:50 GMT

It seems that this only happens with some toolchains. For example, consider the following program, which works if BOOST_BIND_NO_PLACEHOLDERS is defined, but fails to compile otherwise (at least with some toolchains):

//#define BOOST_BIND_NO_PLACEHOLDERS
#include <boost/bind.hpp>
#include <functional>
#include <cstdio>
using namespace std::placeholders;
int main()
{
  const auto g = std::bind(std::puts, _1);
  g("Hello, world!");
}

With gcc-4.9 (admittedly old, but still important for some targets):

$ g++ -Wall -std=c++11 -c -o foo.o foo.cc -I boost_1_64_0
foo.cc: In function ‘int main()’:
foo.cc:10:39: error: reference to ‘_1’ is ambiguous
   const auto g = std::bind(std::puts, _1);
                                       ^
In file included from /usr/include/c++/4.9/memory:79:0,
                 from boost_1_64_0/boost/config/no_tr1/memory.hpp:21,
                 from boost_1_64_0/boost/get_pointer.hpp:14,
                 from boost_1_64_0/boost/bind/mem_fn.hpp:25,
                 from boost_1_64_0/boost/mem_fn.hpp:22,
                 from boost_1_64_0/boost/bind/bind.hpp:26,
                 from boost_1_64_0/boost/bind.hpp:22,
                 from foo.cc:2:
/usr/include/c++/4.9/functional:972:34: note: candidates are: const std::_Placeholder<1> std::placeholders::_1
     extern const _Placeholder<1> _1;
                                  ^
In file included from boost_1_64_0/boost/bind/bind.hpp:2319:0,
                 from boost_1_64_0/boost/bind.hpp:22,
                 from foo.cc:2:
boost_1_64_0/boost/bind/placeholders.hpp:46:38: note:                 constexpr const boost::arg<1> boost::placeholders::_1
 BOOST_STATIC_CONSTEXPR boost::arg<1> _1;                                  ^

Using an online version of gcc-7 at coliru.stacked-crocked.com, it fails in the same way. (I can't post a link or Trac calls this post spam).

I don't see this with modern clang, but gcc-7 is pretty new, so there still seems to be a reason to set BOOST_BIND_NO_PLACEHOLDERS.

BTW, I thought I remembered BOOST_BIND_NO_PLACEHOLDERS being documented in config/user.hpp, but it seems I was mistaken about that, at least in 1.64.0.

bspencer@… — Fri, 07 Jul 2017 21:22:41 GMT

I meant, of course, coliru.stacked-crooked.com