llvm dev - Sep 2018 - Ubuntu LLVM packages incompatible with clang built projects?

Hi folks,

Not sure if this is the right mailing list target, but I'm trying out the
new LLVM 7.0 packages found at http://apt.llvm.org by porting over an
existing LLVM 6.0 project of ours to the new version. In doing so, I found
that the executable always segfaulted at the same spot with no explanation:

0x0000000000fefe33 in
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
llvm::TargetOptions const&, llvm::Optional<llvm::R
eloc::Model>, llvm::Optional<llvm::CodeModel::Model>,
llvm::CodeGenOpt::Level, bool) ()

This happens if I build my project and link it against LLVM 7.0 with either
clang++ 6.1 or clang++ 7.0. This does not happen if I build my project with
g++ 8.

I have also confirmed that building LLVM 7.0 with clang++ and then using
that private build of the libraries fixes the issue.

To summarize, it seems that there's an ABI incompatibility introduced
somewhere, which means LLVM 7.0 compiled with gcc can only be used by other
projects also built with gcc. Is this something that's being investigated
and to be resolved as a fix in 7.1? If not, is there any official release
note that's remarking on this incompatibility?

Thanks,
Kern
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Hi Kern,

We also had issues with mixing GCC/Clang builds when testing the 7.0 
release branch.

My colleague submitted a patch that fixed the issue for us:
* https://reviews.llvm.org/D50710

I no longer have a copy of the error we were seeing to see if it was the 
same, but the fix is to llvm::OptionalStorage and your error message 
involves llvm::Optional.  The patch removes a GCC specific ifdef, and 
hopefully fixes the issue that made that necessary in the first place, 
but we never really knew how the GCC miscompilation was expressed.

It would be interesting to know whether this resolves your issue, but 
regardless we should give the patch a prod.

Regards,
Alastair Murray.


On 27/09/18 08:46, Kern Handa via llvm-dev wrote:
> Hi folks,
>
> Not sure if this is the right mailing list target, but I'm trying out 
> the new LLVM 7.0 packages found at http://apt.llvm.org by porting over 
> an existing LLVM 6.0 project of ours to the new version. In doing so, 
> I found that the executable always segfaulted at the same spot with no 
> explanation:
>
> 0x0000000000fefe33 in 
>
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
> const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef, 
> llvm::TargetOptions const&, llvm::Optional<llvm::R
> eloc::Model>, llvm::Optional<llvm::CodeModel::Model>, 
> llvm::CodeGenOpt::Level, bool) ()
>
> This happens if I build my project and link it against LLVM 7.0 with 
> either clang++ 6.1 or clang++ 7.0. This does not happen if I build my 
> project with g++ 8.
>
> I have also confirmed that building LLVM 7.0 with clang++ and then 
> using that private build of the libraries fixes the issue.
>
> To summarize, it seems that there's an ABI incompatibility introduced 
> somewhere, which means LLVM 7.0 compiled with gcc can only be used by 
> other projects also built with gcc. Is this something that's being 
> investigated and to be resolved as a fix in 7.1? If not, is there any 
> official release note that's remarking on this incompatibility?
>
> Thanks,
> Kern
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
-- 
Alastair Murray
Principal Software Engineer, Compilers
Codeplay Software Ltd
Level C, Argyle House, 3 Lady Lawson St., Edinburgh, EH3 9DR
Tel: 0131 466 0503
Fax: 0131 557 6600
Website: http://www.codeplay.com
Twitter: https://twitter.com/codeplaysoft

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Just be aware that those ifdefs were recommitted and reverted several
times, so I'm not sure what the state is.

On Fri, Sep 28, 2018 at 8:48 AM Alastair Murray via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi Kern,
>
> We also had issues with mixing GCC/Clang builds when testing the 7.0
> release branch.
>
> My colleague submitted a patch that fixed the issue for us:
> * https://reviews.llvm.org/D50710
>
> I no longer have a copy of the error we were seeing to see if it was the
> same, but the fix is to llvm::OptionalStorage and your error message
> involves llvm::Optional.  The patch removes a GCC specific ifdef, and
> hopefully fixes the issue that made that necessary in the first place, but
> we never really knew how the GCC miscompilation was expressed.
>
> It would be interesting to know whether this resolves your issue, but
> regardless we should give the patch a prod.
>
> Regards,
> Alastair Murray.
>
> On 27/09/18 08:46, Kern Handa via llvm-dev wrote:
>
> Hi folks,
>
> Not sure if this is the right mailing list target, but I'm trying out
the
> new LLVM 7.0 packages found at http://apt.llvm.org by porting over an
> existing LLVM 6.0 project of ours to the new version. In doing so, I found
> that the executable always segfaulted at the same spot with no explanation:
>
> 0x0000000000fefe33 in
>
llvm::RegisterTargetMachine<llvm::X86TargetMachine>::Allocator(llvm::Target
> const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
> llvm::TargetOptions const&, llvm::Optional<llvm::R
> eloc::Model>, llvm::Optional<llvm::CodeModel::Model>,
> llvm::CodeGenOpt::Level, bool) ()
>
> This happens if I build my project and link it against LLVM 7.0 with
> either clang++ 6.1 or clang++ 7.0. This does not happen if I build my
> project with g++ 8.
>
> I have also confirmed that building LLVM 7.0 with clang++ and then using
> that private build of the libraries fixes the issue.
>
> To summarize, it seems that there's an ABI incompatibility introduced
> somewhere, which means LLVM 7.0 compiled with gcc can only be used by other
> projects also built with gcc. Is this something that's being
investigated
> and to be resolved as a fix in 7.1? If not, is there any official release
> note that's remarking on this incompatibility?
>
> Thanks,
> Kern
>
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttp://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
> --
> Alastair Murray
> Principal Software Engineer, Compilers
> Codeplay Software Ltd
> Level C, Argyle House, 3 Lady Lawson St., Edinburgh, EH3 9DR
> Tel: 0131 466 0503
> Fax: 0131 557 6600
> Website: http://www.codeplay.com
> Twitter: https://twitter.com/codeplaysoft
>
> This email and any attachments may contain confidential and /or privileged
information and
> is for use by the addressee only. If you are not the intended recipient,
please notify
> Codeplay Software Ltd immediately and delete the message from your
computer. You may not
> copy or forward it, or use or disclose its contents to any other person.
Any views or other
> information in this message which do not relate to our business are not
authorized by
> Codeplay software Ltd, nor does this message form part of any contract
unless so stated.
> As internet communications are capable of data corruption Codeplay Software
Ltd does not
> accept any responsibility for any changes made to this message after it was
sent. Please
> note that Codeplay Software Ltd does not accept any liability or
responsibility for viruses
> and it is your responsibility to scan any attachments.
> Company registered in England and Wales, number: 04567874
> Registered office: Regent House, 316 Beulah Hill, London, United Kingdom,
SE19 3HF
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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