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From: "lewissbaker.opensource at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/95736] coroutine method improperly copies awaitable
Date: Thu, 18 Jun 2020 15:50:36 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95736

Lewis Baker <lewissbaker.opensource at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |lewissbaker.opensource@gmai
                   |                            |l.com

--- Comment #1 from Lewis Baker <lewissbaker.opensource at gmail dot com> -=
--
I've also investigated this a bit more and have annotated the assembly of t=
he
code being generated by GCC in this example (slightly modified).

https://godbolt.org/z/_HJNHC

Immediately before the 'co_await foo' expression the compiler generates
a copy of the this->foo member into the coroutine frame. But it does
this doing the equivalent of a memcpy() rather than calling the
copy-constructor.

The compiler should not be making this copy of the operand to 'co_await'
and should instead be passing the address of the 'this->foo' member to the
as the implicit object parameter in the call to
await_ready/await_suspend/await_resume.=