Compilation failure with 1.83

[SoapGentoo]

We're seeing one specific failure of Boost.Signals2 in our Gentoo package tree: Bug 912309

This code used to compile fine under Boost 1.82. The offending line is:

stanzaChannel_->onPresenceReceived.disconnect(boost::ref(onPresenceReceived));

here stanzaChannel_->onPresenceReceived is of type boost::signals2::signal<void (std::shared_ptr<Message>)> and the onPresenceReceived argument on the right-hand side is of type boost::signals2::signal<void (std::shared_ptr<Message>)> too. The error boils down to an ambiguous overload

/usr/include/boost/function_equal.hpp:17:14: error: no match for 'operator==' (operand types are 'const boost::reference_wrapper<boost::signals2::signal<void(std::shared_ptr<Swift::Presence>)> >' and 'const boost::reference_wrapper<boost::signals2::signal<void(std::shared_ptr<Swift::Presence>)> >')
   17 |   { return f == g; }
      | 

Do you have any ideas or guidance that could help us fix this locally? Upstream seems mostly gone, and this is the last bug for us in Boost 1.83. Paging in @pdimov who recommended I file a bug here.

[fmhess]

To fix, you'd need to patch boost.function and boost.signals2 from development, or wait for boost 1.84, or compile against a version of the c++ standard which is not c++20

[SoapGentoo]

@fmhess thanks, could you point me to the commits that purport to fix this? I can try them locally, since boost 1.84 is still some time away

[ConiKost]

@fmhess ping. Could you please have a look, which commits are needed for fix? Thank you!

[thesamesam]

Ping

[SoapGentoo]

Unfortunately, the code still fails with boost 1.84 😢

[fmhess]

Ok, I fixed disconnection by slots which are signals, and slots which are wrapped in a boost::reference_wrapper. The fix is on the develop branch with the following two commits:

commit 2ba258f
commit 4d994bb

[ConiKost]

I can confirm, that appliying those patches against boost-1.83 (haven't tested boost-1.84), makes it compiling again.