[cfe-dev] Current state of libcxx compatibility with libstdc++

Martin J. O'Riordan via cfe-dev cfe-dev at lists.llvm.org
Tue Aug 9 13:42:24 PDT 2016

Thanks Craig.

Yes, I had read this paper when Herb submitted it, and it really does say the same things; and that must have been more than 2 years ago.

Even earlier, I and others wrote the TR on embedded system (Technical Report on C++ Performance [ISO-IEC TR 18015-2006(E)]) and that was 10 years ago!

None of these problems are new unfortunately, but they still are not solved.


-----Original Message-----
From: cfe-dev [mailto:cfe-dev-bounces at lists.llvm.org] On Behalf Of Craig, Ben via cfe-dev
Sent: 09 August 2016 21:32
To: cfe-dev at lists.llvm.org
Subject: Re: [cfe-dev] Current state of libcxx compatibility with libstdc++

On 8/9/2016 2:29 PM, Martin J. O'Riordan via cfe-dev wrote:

> So this has gone off on a tangent from whether or not LibC++ should be 
> binary compatible with 'libstdc++' (sorry for hijacking that 
> discussion) - and for the record I don't think that they "should" be, 
> and I don't think that they "can" be - but it does raise the broader 
> issue regarding whether successive versions of a C++ library from the 
> same vendor (LLVM/CLang in this case) should be binary compatible.  
> And this is a trade-off - either we have 100% implementation hiding 
> (i.e. a true black-box interface) which will incur a runtime penalty 
> (space and/or time) - or we have a compromise which allows the 
> implementer to provide more efficient (space/time) implementations 
> with successive revisions, but at the expense of binary portability.
> There is no perfect answer.
> 	MartinO
You should look at this paper:

I haven't heard much activity on it since it was released, so maybe it was discussed and dropped.

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