[Bug c++/95346] [coroutines] coroutine return-type should be initialised with rvalue if different from get_return_object() return-type

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95346

--- Comment #2 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:4f2d05ef0142d269964e165c14c6f7fe4bdfd5a3

commit r11-952-g4f2d05ef0142d269964e165c14c6f7fe4bdfd5a3
Author: Iain Sandoe <iain@sandoe.co.uk>
Date:   Thu Jun 4 17:14:37 2020 +0100

    coroutines: Fix missed ramp function return copy elision [PR95346].

    Confusingly, "get_return_object ()" can do two things:
    - Firstly it can provide the return object for the ramp function (as
      the name suggests).
    - Secondly if the type of the ramp function is different from that
      of the get_return_object call, this is used as a single parameter
      to a CTOR for the ramp's return type.

    In the first case we can rely on finish_return_stmt () to do the
    necessary processing for copy elision.
    In the second case, we should have passed a prvalue to the CTOR as
    per the standard comment, but I had omitted the rvalue () call.  Fixed
    thus.

    gcc/cp/ChangeLog:

            PR c++/95346
            * coroutines.cc (morph_fn_to_coro): Ensure that the get-
            return-object is constructed correctly; When it is not the
            final return value, pass it to the CTOR of the return type
            as an rvalue, per the standard comment.

    gcc/testsuite/ChangeLog:

            PR c++/95346
            * g++.dg/coroutines/pr95346.C: New test.