bug in gcc/cp/coroutines.cc line 4688

[Andrew Pinski]

On Sat, Jan 18, 2025 at 2:12 PM Lee Brown via Gcc <gcc@gcc.gnu.org> wrote:
>
> Just to be clear,   the appended 17 lines of very simple code breaks gcc
> on every platform where <coroutine> header does not have <new> in its
> include hierarchy....which I assume to be every platform.

See the discussion in the bug report:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95505 . That is there is
no bug in libstdc++ nor in GCC in theory. Any use of
get_return_object_on_allocation_failure for the promise_type requires
new to be included. Now there should be a note about a missing include
of new but that is just a small diagnostic issue.

Thanks,
Andrew Pinski

>
> 1) place code below in main.cpp
>
> 2) g++ -std=c++20 main.cpp
>
> and you get
>
> main.cxx: In function 'my_co do_co()':
> main.cxx:16:7: error:
> 'my_co::promise_type::get_return_object_on_allocation_failure()' is
> provided by 'std::__n4861::__coroutine_traits_impl<my_co,
> void>::promise_type' {aka 'my_co::promise_type'} but *'std::nothrow'
> cannot be found*
>     16 | my_co do_co() { co_return; }
>        |       ^~~~~
>
>
> Here's the code:
>
> // begin code --------------------------------
>
> #include <coroutine>
>
> struct my_co {
>      struct promise_type {
>          static    my_co get_return_object_on_allocation_failure() {
> return my_co(); }
>                  my_co get_return_object()     { return my_co(); }
>
>          std::suspend_always initial_suspend() noexcept     { return {}; }
>          std::suspend_always final_suspend() noexcept     { return {}; }
>          void                 return_void()                 {}
>          void                 unhandled_exception()         {}
>      };
> };
>
> my_co do_co() { co_return; }
>
> int main()
> {
>      do_co();
>      return 0;
> }
>
> // end code ----------------------------
>