Boost C++ Libraries: Ticket #12123: Using Boost.Signals2 with Boost.Variant leads to compilation error, MSVC 14 (suspected compiler bug)

attachment set

Tue, 12 Apr 2016 18:47:14 GMT

attachment → error.log

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Tue, 12 Apr 2016 18:47:49 GMT

attachment → Source.cpp

Reduced sample code illustrating code that fails to compile

Tue, 12 Apr 2016 22:09:05 GMT

After more troubleshooting today, I am unsure whether the problem lies within Boost.Signals2 or Boost.Variant. I was able to reproduce the problem with just Boost.Variant in my project, but I was unable to reproduce it without Boost.Signals2 in a reduced test case. This seems to hint that the problem lies more with Boost.Variant, although I will leave the component as Boost.Signals2 until someone with more knowledge can determine that.

While doing more reading and testing, could this issue be related to the infamous MSVC extension allowing for temporary variables to bind to non-const references? I am able to compile the program in MSVC by using this extension (making parameters be non-const references).

cc changed

raad@… — Thu, 14 Apr 2016 21:28:47 GMT

cc raad@… added

The problem is boost::variant's unconstrained templated constructor, which cannot be used in C++17's std::tuple.

There are two related boost::varant bug reports: https://svn.boost.org/trac/boost/ticket/5871 https://svn.boost.org/trac/boost/ticket/11602

The problem mentioned in a Visual C++ blog post: https://blogs.msdn.microsoft.com/vcblog/2016/04/14/stl-fixes-in-vs-2015-update-2/

tschenser@… — Tue, 19 Apr 2016 07:08:22 GMT

boost::any seems to have the same unconstrained template constructor, see my problem report https://svn.boost.org/trac/boost/ticket/12110.

As a possible workarround I may suggest you to to #define BOOST_NO_CXX11_HDR_TUPLE

Frank Mori Hess — Fri, 22 Apr 2016 05:51:29 GMT

This patch seems to have fixed the similar issue reported in #12110 :

https://github.com/boostorg/signals2/commit/db0d3f55cccb2dbd8ab88a146af9100f2fca740b

raad@… — Fri, 22 Apr 2016 07:02:53 GMT

I can confirm this fixes the problem with boost::variant for me. Thanks a lot!

status changed; resolution set

Frank Mori Hess — Sun, 15 May 2016 04:21:20 GMT

status new → closed
resolution → fixed

Changes merged to master, was fixed for 1.61 release.