Re: [boost] [core] Breaking change to boost::ref in 1.56

Subject: Re: [boost] [core] Breaking change to boost::ref in 1.56
From: Peter Dimov (lists_at_[hidden])
Date: 2014-07-13 05:06:56

Eric Niebler wrote:
> While investigating a failure[^1] in proto, I discovered the following 
> change to boost::ref:
>
> https://github.com/boostorg/core/commit/af629ffa59094048c335609f285afe342fd1f1e4
>
> This failure was caused by the following change to boost::ref by Agustín 
> Bergé (K-ballo):
>
> https://github.com/boostorg/core/commit/af629ffa59094048c335609f285afe342fd1f1e4
>
> I didn't see any discussion about this change. (Was there one?) I can 
> guess why it was made: to make boost::ref behave like std::ref, which does 
> "reference collapsing" with reference_wrapper (which IMO is broken, and I 
> unsuccessfully argued that in the committee when this was voted in). The 
> problem is, it's a breaking interface change to one of the oldest, most 
> heavily used, and stable pieces of Boost. It pretty massively breaks a 
> major part of Boost.Proto's interface (proto::make_expr). I've hacked 
> around the problem in Proto's tests, but this is going to break end-user 
> code, and I don't know what I'm going to tell people.
>
> I don't like differences between boost and std. But I also don't like 
> breaking code. What do we want here?

We want to revert the change, unless someone (quickly) succeeds in 
convincing us not to.

> [^1]:
> http://www.boost.org/development/tests/develop/developer/output/teeks99-03j-Ubuntu12-04-64-boost-bin-v2-libs-proto-test-mem_ptr-test-clang-linux-3-4-debug-link-static.html