[Bug c++/100897] Symmetric transfer does not prevent stack-overflow for C++20 coroutines

["iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100897

Iain Sandoe <iains at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-06-11
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=94794,
                   |                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=95137

--- Comment #1 from Iain Sandoe <iains at gcc dot gnu.org> ---
for symmetric transfer to work without stack overflow, it relies on an indirect
tailcall.

For some GCC targets indirect tail-calls are not available without some
additional support (see PR94794).

I tried to reproduce this (with a test case I use regularly for this) on a
target that normally completes symmetric transfers successfully when the
optimisation level is > 1. (x86_64, darwin).

The fail also occurs with my regular test case with -fsanitize=address - so, it
seems that the inclusion of the address sanitiser is preventing or interfering
with the tailcall.  Note that there are also other known issues with coroutines
and the sanitizers (PR95137).