Context does not properly check support for std::integer_sequence

[Emile Cormier]

When I build Boost 1.58 with C++11 support on GCC 4.8.2, it fails to build the context library. This is due to the library attempting to use std::index_sequence:

In file included from libs/context/src/execution_context.cpp:11:0:
./boost/context/execution_context.hpp:202:52: error: ‘std::index_sequence’ has not been declared

std::index_sequence is a feature only available in C++14.

A workaround would be:

1. First build a C++11-enabled Boost using the --without-context option
2. Build the missing context library using --with-context, making sure that -std=c++11 is NOT added to the cxxflags

My platform is GCC 4.8.2, x86_64-linux-gnu, Linux Mint 17 (based on Ubuntu 14.04)

[olli]

Class execution_context can only be compiled with C++-14 - the code uses test macros for several C++11/C++14 features in order to enable building class execution_context. Unfortunately, boost is missing a test macro for 'std::index_sequence'. I already requested for supporting the required macro.

[olli]

see - ​http://lists.boost.org/Archives/boost/2015/02/220151.php

[olli]

please re-assign if macro is available

[olli]

I've added a pull-request for boost.config (​https://github.com/boostorg/config/pull/57) - which solves the problem for GCC and CLANG. Unfortunately I'm not familiar with the other compiler (maybe defining BOOST_NO_CXX14_INTEGER_SEQUENCE per default at first).

[olli]

test of

defined(__cpp_lib_integer_sequence) && (__cpp_lib_integer_sequence < 201304)

[Emile Cormier]

Has this fix been pushed to GitHub yet?

[Emile Cormier]

Nevermind, I found your latest Boost.Config PR: ​https://github.com/boostorg/config/pull/58

Thank you for fixing this! :-)

While I wait for the next Boost release, can I simply add -DBOOST_NO_CXX14_INTEGER_SEQUENCE while building Boost to avoid the compiler errors I originally reported?