[cfe-dev] Control selected GCC installation / selected libstdc++ version?

Kevin Funk via cfe-dev cfe-dev at lists.llvm.org
Thu Mar 10 06:53:44 PST 2016


On Saturday, March 5, 2016 4:07:43 PM CET Kevin Funk via cfe-dev wrote:
> Heya,
> 
> I just installed GCC6 on my system (which obviously comes with a new
> libstdc+ +), and this, unfortunately, breaks Clang.
> 
> Long story short: In this particular case I can't build LLVM anymore, since
> clang errors out:
> 
> /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0/../../../../include/c++/6.0.0/
> tuple:1381:14: error: no matching constructor for initialization of
> 'tuple<llvm::LexicalScope *&&, const llvm::DILocalScope *&&, nullptr_t &&,
> bool &&>'
>     { return tuple<_Elements&&...>(std::forward<_Elements>(__args)...); }
>              ^                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ...
> 
> 
> I'm not interested in solving the error, I'm more concerned about this: Is
> it possible to force Clang into using a specific libstdc++ version? Right
> now it seems to just choose the highest version available(?)
> 
> # clang++-3.6 -E -v
> Ubuntu clang version 3.6.2-3ubuntu1 (tags/RELEASE_362/final) (based on LLVM
> 3.6.2)
> Target: x86_64-pc-linux-gnu
> Thread model: posix
> (snip)
> Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
> Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.1
> Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.0.0
> Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.0.0
> Candidate multilib: .;@m64
> Selected multilib: .;@m64
> 
> ^ How can I force clang to use /usr/lib/gcc/x86_64-linux-gnu/5.3.1 instead,
> for instance?
> 
> Is that even possible? I had a brief look at tools/clang/lib/Driver/
> ToolChains.cpp, but couldn't find any knobs I could use from the
> command-line.

Bump.

Any idea? Am I missing something?

Do you a think a patch which introduces an env var setting for specifying the 
desired libstdc++ version would be acceptable?

Cheers,
Kevin

> Cheers,
> Kevin


-- 
Kevin Funk | kfunk at kde.org | http://kfunk.org
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