Re: [Boost-users] [boost::shared_ptr] Easy to violate the One Definition Rule / C++11 / Check für standard used to compile Boo

Subject: Re: [Boost-users] [boost::shared_ptr] Easy to violate the One Definition Rule / C++11 / Check für standard used to compile Boo
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2014-01-15 12:03:09

On 15 Jan 2014 at 15:45, beet wrote:

> So what may happen here is that my main application uses a different
> boost::shared_ptr than the Boost libraries I want to link with. To me
> this seems to violate the one-definition rule (and may happen with other
> Boost libraries as well).

That happens all over the place always in any C++11 build mixed with 
C++03 binaries. It's normally not an issue because the library author 
will have taken care to ensure ABI compatibility irrespective of how 
their code is built.

Yes it is a violation of the C++ standard, but that's also normally 
not an issue. There are very few - if any - real world C++ codebases 
of any size which are fully valid and legal programs according to the 
standard. I personally can't think of one I've ever seen, not ever.

> Hence: Is there any way I can check (e.g. through some #define provided
> by Boost) what C++ standard it has been compiled with ?

Boost provides a series of C++11 header check macros as various C++11 
compilers provide varying amounts of C++11. You could encode these 
into linker symbols, and use those as fingerprints. Boost does not do 
this currently to my knowledge.

I once asked GCC to add a magic symbol fingerprint to all ELF 
binaries to say what C++ version they were built with. I figured it 
would be extremely useful to know for debugging. I was roundly told 
no, period.

On MSVC, things are much easier as the version of MSVCRT is iterated 
every MSVC release. That lets you very easily know what compiler 
built what library by examining what MSVCRT version it uses.

Niall

-- 
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