Adding a new thread model to GCC

[Jonathan Wakely]

How does this compare with Eric B's proposal at
https://gcc.gnu.org/legacy-ml/gcc-patches/2019-06/msg01840.html ?

It would be good if we can accept one of them for GCC 13, but I don't
know Windows well enough to determine which is better.

On Sat, 1 Oct 2022 at 19:35, LIU Hao via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> Greetings.
>
> After some years I think it's time to put on this topic again.
>
> This patch series is an attempt to add a new thread model basing on the mcfgthread library
> (https://github.com/lhmouse/mcfgthread), which provides efficient implementations of mutexes,
> condition variables, once flags, etc. for native Windows.
>
>
> The first patch is necessary because somewhere in libgfortran, `pthread_t` is referenced. If the
> thread model is not `posix`, it fails to compile.
>
> The second patch implements `std::thread::hardware_concurrency()` for non-posix thread models. This
> would also work for the win32 thread model if `std::thread` would be supported in the future.
>
> The third patch adds the `mcf` thread model for GCC and its libraries. A new builtin macro
> `__USING_MCFGTHREAD__` is added to indicate whether this new thread model is in effect. This grants
> `std::mutex` and `std::once_flag` trivial destructors; `std::condition_variable` is a bit
> unfortunate because its destructor is non-trivial, but in reality no cleanup is performed.
>
>
> I have been bootstrapping GCC with the MCF thread model for more than five years. At the moment, C,
> C++ and Fortran are supported. Ada is untested because I don't know how to bootstrap it. Objective-C
> is not supported, because threading APIs for libobjc have not been implemented.
>
> Please review. If there are any changes that I have to make, let me know.
>
>
> --
> Best regards,
> LIU Hao