https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97587
Bug ID: 97587
Summary: [coroutines] promise_type constructor is called with
original parameters, not parameter copies
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jehelset at gmail dot com
Target Milestone: ---
Created attachment 49443
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49443&action=edit
Program that results in assertion-failure due to wrong arguments to promise.
The promise-type constructor should be called with the parameter copies from
the coroutine-frame. I couldn't quite understand that this is supposed to be
the case from the current draft of the standard, but I got some help from Lewis
Baker who also referred me to this rewording, where in the previous version it
is clear:
https://github.com/cplusplus/draft/commit/0b4ab68a54e197eba9d894a8f91270bb0dcdb546
The attached code triggers an assertion that show that this is not the case on
gcc. I initially had the problem on gcc-10.2.0, but reproduced it on gcc-trunk
on godbolt. Compile either version with -fcoroutines, or see
https://gcc.godbolt.org/z/j16Wqx.
I speculated that the logic here,
https://github.com/gcc-mirror/gcc/blob/master/gcc/cp/coroutines.cc#L4491-L4494,
was inverted. It seemed to pass the copied version of a by-reference parameter,
but the original version of a by-value parameter. The opposite would not
trigger the assertion. But I am not that familiar.
