[LLVMdev] [cfe-dev] Cygwin bootstrap is incompatible with <mutex> (and most other threading C++11 libraries)

[Reid Kleckner]

On Wed, Jun 25, 2014 at 7:01 AM, NAKAMURA Takumi <geek4civic at gmail.com>
wrote:

> I reverted <mutex>, since also clang-native-mingw32-win7 had been broken.
> There were two ways of issues, in mingw32 (not w64) and cygwin.
>
> For mingw32, it seems <mutex> is configured without __thread. Some
> features, like "once", are unavailable.
> When we reintroduce <mutex> in the tree, we should make mingw32
> builder obsoleted or migrated to mingw-w64.
>

Other users reported that mingw64 doesn't support <mutex> either.  IMO it's
important to support the most popular distribution of GCC on Windows, which
I believe is mingw64 these days.  I'm fine with dropping Cygwin
self-hosting support if that's the only thing blocking us from using
std::mutex, but I think mingw64 is the real blocker.


> For Cygwin, I can suggest an option,
>
> 3a) Implement __thread in near future. Till then,
>
>   3a-1) Give up bootstrapping. Cygwin-g++-4.8 can build the tree, though.
>   3a-2) Apply local patch in the builder to suppress unsupported
> features like <mutex>.
>
> Conclusion: Go ahead!
> I supposed, when I reverted <mutex>, it were trivial. I won't disturb
> any more if we are going toward c++11.
>

Thanks for that, it's important to keep the bots green.  The bot
notifications were probably lost in the ether, and I didn't think to check
them manually.
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