Re: devel Digest, Vol 196, Issue 58

[Florian Weimer]

* Jeff Law:

> As we both know, GCC has had ABI bugs as well.  Both compilers strive
> to be ABI compatible with each other and we should continue to work
> together to find and address such issues.  SImilarly both compilers
> are going to have codegen issues, or rejects-valid-code bugs.
> Ultimately they're just bugs and I don't see that one toolchain or the
> other is inherently better than the other, particularly WRT ABI
> issues.

More problematic are not ABI bugs, but the cases where the ABI
divergence is a matter of opinion (more or less).

I think we really should figure out what to do about the alignment of
_Atomic long long on 32-bit.  GCC has 4, Clang has 8.  Clang seems to be
correct here.  This also has implications for the use of libatomic.

Thanks,
Florian
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Re: devel Digest, Vol 196, Issue 58

[Jeff Law]

On Fri, 2020-06-05 at 10:22 +, devel-requ...@lists.fedoraproject.org wrote:
> Date: Fri, 5 Jun 2020 11:19:54 +0200
> 
> From: Jakub Jelinek 
> 
> Subject: Re: Fedora 33 System-Wide Change proposal: CompilerPolicy
> 
> Change
> 
> To: Development discussions related to Fedora
> 
> 
> 
> Message-ID: <20200605091954.GH8462@tucnak>
> 
> Content-Type: text/plain; charset=us-ascii
> 
> 
> 
> On Fri, Jun 05, 2020 at 09:52:09AM +0200, Kevin Kofler wrote:
> 
> > I do not see why we should allow yet another special case for Firefox, nor 
> > why we should let random packages make their own choice of compiler and 
> > risk 
> > running into hidden binary incompatibilities. We have a system compiler for 
> > a reason.
> 
> 
> I'll note that there are some even not really hidden binary
> 
> incompatibilities, where LLVM diverges from the psABI for years, it has been
> 
> reported and nothing has been changed.
> 
> So if a library is built with clang/LLVM and used by GCC built package or
> 
> vice versa, one might very well run into those (this is e.g. about passing
> 
> std::byte or other scoped enums with char/short underlying type by value, or
> 
> in some cases even about passing char/short arguments).
> 
> And of course unknown ABI bugs on both sides.
As we both know, GCC has had ABI bugs as well.  Both compilers strive to be ABI
compatible with each other and we should continue to work together to find and
address such issues.  SImilarly both compilers are going to have codegen issues,
or rejects-valid-code bugs.  Ultimately they're just bugs and I don't see that
one toolchain or the other is inherently better than the other, particularly WRT
ABI issues.


jeff
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