Re: Asio, gcc and -fconcepts

From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2020-04-06 18:27:51

On 2020-04-06 20:01, Richard Hodges via Boost wrote:
> Dear all,
> 
> With the upcoming Boost 1.73 release imminent, I felt it was worthwhile
> pointing out that latest gcc has a problem with Asio if the `-fconcepts`
> command line flag is set.
> 
> There is an issue in the Boost.Asio repo here relating to the manifestation
> of the bug in MSVC:
> 
> https://github.com/boostorg/asio/issues/312
> 
> and an issue here in the Boost.Beast repo:
> 
> https://github.com/boostorg/beast/issues/1884
> 
> It seems that the file boost/asio/detail/config.hpp was written when
> concepts support was not widespread and still in the concepts.ts stage.
> 
> The syntax and capabilities of concepts were subtly changed during
> standardisation, with gcc and MSVC only supporting the C++20 dialect.
> 
> Thus, compiling an Asio-based program with concepts enabled in either of
> gcc or MSVC fails unconditionally.
> 
> I'm wondering if anyone has Chris' ear and might ask him to indulge us with
> a fix prior to the 1.73 release.
> 
> I fear that by the time Boost 1.73 is in mainstream use, C++20 will be upon
> us we'll see an increase in issues and a loss of reputation as a result.

I think, your best bet is to report the problem to the upstream ASIO 
project[1] and explicitly ask for a fix in Boost.ASIO ASAP.

[1]: https://github.com/chriskohlhoff/asio/