Boost C++ Libraries: Ticket #12236: BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES for msvc 2015

fsmoke@… — Mon, 30 May 2016 18:01:46 GMT

Sorry '/*' wrongly moved out is must be around /*(defined(_MSC_VER) && (_MSC_VER <= 1900))*/

anonymous — Mon, 30 May 2016 18:46:49 GMT

oh variant based on mpl - why?

#if !defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)

template < typename... T > struct make_variant_list {

typedef typename mpl::list< T... >::type type;

};

#else defined(BOOST_VARIANT_DO_NOT_USE_VARIADIC_TEMPLATES)

so it's check is irrelevant cos we has limitation of mpl :( (20 arguments by default)

so i have another question - when limitations will be removed?

owner changed

Antony Polukhin — Thu, 02 Jun 2016 19:30:44 GMT

owner changed from ebf to Antony Polukhin

I do not have access to the latest msvc2015 right now. Could you apply your patch and run all the tests from boost_root/libs/variant/test. Just go to that folder and run ..\..\..\b2 from it.

If everything is OK, than it's a good sign not to increment 1900 next time :) Unfortunately it's impossible to enable variadics for _MSC_VER == 1900, because there's no known to me way to distinguish vs2015 update 2 from older versions (update 1 and before) and Boost must be able to run on any compiler.

oh variant based on mpl - why?

Variant was created long before variadic templates appeared. Since then variant uses MPL.

when limitations will be removed?

When Boost.MPL will be transfered to variadic templates. That's a big task and nobody has time or will to do it right now. However pull requests are always welcomed ;)

fsmoke@… — Fri, 03 Jun 2016 07:06:44 GMT

Replying to apolukhin:

I do not have access to the latest msvc2015 right now. Could you apply your patch and run all the tests from boost_root/libs/variant/test. Just go to that folder and run ..\..\..\b2 from it.

I'll try to do this as soon as posible

If everything is OK, than it's a good sign not to increment 1900 next time :) Unfortunately it's impossible to enable variadics for _MSC_VER == 1900, because there's no known to me way to distinguish vs2015 update 2 from older versions (update 1 and before) and Boost must be able to run on any compiler.

May be you can try _MSC_FULL_VER instead of _MSC_VER

When Boost.MPL will be transfered to variadic templates. That's a big task and nobody has time or will to do it right now. However pull requests are always welcomed ;)

Yeah it's great job to do this. But i heard new standard will contain std::variant

status changed; resolution set

Antony Polukhin — Wed, 18 Jan 2017 22:28:33 GMT

status new → closed
resolution → wontfix

I'm afraid that MSVC2015 still has issues with variadic templates.