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Subject: [Bug c++/103868] ICE at end of coroutine when using asio
Date: Thu, 28 Apr 2022 12:51:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103868

--- Comment #6 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:9cb1f565a91e2dd57098c43593954b57c065a19b

commit r12-8307-g9cb1f565a91e2dd57098c43593954b57c065a19b
Author: Nathan Sidwell <nathan@acm.org>
Date:   Sun Apr 3 11:35:03 2022 +0100

    c++, coroutines: Avoid expanding within templates [PR103868]

    This is a forward-port of a patch by Nathan (against 10.x) which fixes =
an
open
    PR.

    We are ICEing because we ended up tsubst_copying something that had alr=
eady
    been tsubst, leading to an assert failure (mostly such repeated tsubsti=
ng
is
    harmless).

    We had a non-dependent co_await in a non-dependent-type template fn, so=
 we
    processed it at definition time, and then reprocessed at instantiation
time.
    We fix this here by deferring substitution while processing templates.

    Additional observations (for a better future fix, in the GCC13 timescal=
e):

    Exprs only have dependent type if at least one operand is dependent whi=
ch
was
    what the current code was intending to do.  Coroutines have the additio=
nal
    wrinkle, that the current fn's type is an implicit operand.

    So, if the coroutine function's type is not dependent, and the operand =
is
not
    dependent, we should determine the type of the co_await expression using
the
    DEPENDENT_EXPR wrapper machinery.  That allows us to determine the
    subexpression type, but leave its operand unchanged and then instantiat=
e it
    later.

            PR c++/103868

    gcc/cp/ChangeLog:

            * coroutines.cc (finish_co_await_expr): Do not process
non-dependent
            coroutine expressions at template definition time.
            (finish_co_yield_expr): Likewise.
            (finish_co_return_stmt): Likewise.

    gcc/testsuite/ChangeLog:

            * g++.dg/coroutines/pr103868.C: New test.

    Co-Authored-by: Iain Sandoe <iain@sandoe.co.uk>=