[Bug c++/95050] coroutine: no "mandatory copy elision" for prvalue await_resume expression.

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95050

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Iain D Sandoe <iains@gcc.gnu.org>:

https://gcc.gnu.org/g:324276ff9b1aa5128e5cb9f5d43182d1ebab0752

commit r11-835-g324276ff9b1aa5128e5cb9f5d43182d1ebab0752
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Tue Jun 2 16:47:54 2020 +0100

    coroutines: Wrap co_await in a target expr where needed [PR95050]

    Since the co_await expression is mostly opaque to the existing
    machinery, we were hiding the details of the await_resume return
    value.  If that needs to be wrapped in a target expression, then
    emulate this with the whole co_await.  Similarly, if the await
    expression we build in response to co_await p.yield_value (e)
    is wrapped in a target expression, then we need to transfer that
    wrapper to the resultant CO_YIELD_EXPR (which is, itself, just
    a proxy for the underlying co_await).

    gcc/cp/ChangeLog:

            PR c++/95050
            * coroutines.cc (build_co_await): Wrap the co_await expression
            in a TARGET_EXPR, where needed.
            (finish_co_yield_expr): Likewise.

    gcc/testsuite/ChangeLog:

            PR c++/95050
            * g++.dg/coroutines/pr95050.C: New test.