Re: [boost] ABI issues with -std

Subject: Re: [boost] ABI issues with -std
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2018-08-20 08:23:49

On 08/20/18 10:37, Olaf van der Spek wrote:
> On Sun, Aug 19, 2018 at 10:57 PM, Andrey Semashev via Boost
> <boost_at_[hidden]> wrote:
>> I solved this in Boost.Log this way:
>>
>>    struct Y
>>    {
>>       void f( X const& x );
>>
>>    #if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
>>
>>       void f( X&& x ) { f_move(x); }
>>
>>    #endif
>>
>>    private:
>>      void f_move(X& x);
>>    };
> 
> Only works if void f( X&& x ) is inlined and even then it still
> violates ODR doesn't it?

If `f( X&& x )` is not inlined then it means it is ODR-used in the 
user's code and left there as a standalone function. I don't see the 
problem.

ODR is violated but not in the harmful way. ABI is the same, API is 
99.9% compatible (leaving 0.1% for weird cases where you try to exchange 
a pointer to Y::f between code bases for C++03 and C++11).

>> As a slightly different variant of the Boost.System2 solution, I can
>> suggest building multiple Boost.System binaries, one per ABI we can
>> support.
> 
> That'd require library name mangling on Linux and adding the std level
> to the name..

Not necessarilly. The base name of Boost.System with the new ABI could 
be different.