[PATCH] D46723: Require GCC 5.1 and LLVM 3.5 at a minimum

[Evgeny Astigeevich via Phabricator via llvm-commits]

eastig added a comment.

In https://reviews.llvm.org/D46723#1096542, @eastig wrote:

> In https://reviews.llvm.org/D46723#1096058, @jfb wrote:
>
> > In https://reviews.llvm.org/D46723#1096025, @eastig wrote:
> >
> > > We might need to play with _GLIBCXX_USE_CXX11_ABI=0 and the -Wabi-tag option to mitigate libstdc++ ABI issues.
> >
> >
> > Agreed. Do you have a Linux machine to try it out? I don't have a VM set up with an older distro at the moment. It would be useful to see which libstdc++ features are used by LLVM when compiled with GCC 5.1 (as well as with LLVM 3.4 when using libstdc++).
>
>
> I have a machine with Ubuntu 14.04. I'll run experiments.


I ran experiments. I installed gcc 5 from ppa:ubuntu-toolchain-r/test on Ubuntu 14.04. It was gcc 5.5. It updated the system libstdc++ to GLIBCXX_3.4.21. Clang/LLVM built with it won't run on clean Ubuntu 14.04. The library is built with the old library ABI.
The option '-Wabi-tag' did not provide any information because no ABI tags are used in the library header files. The option works for gcc on Ubuntu 16.04. With it enabled I managed to find 2069 places having library ABI issues (2041 - string; 28 - list).


Repository:
  rL LLVM

https://reviews.llvm.org/D46723