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From: "iains at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/101118] coroutines: unexpected ODR warning for coroutine
 frame type in LTO builds
Date: Fri, 18 Jun 2021 10:46:37 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101118

--- Comment #2 from Iain Sandoe <iains at gcc dot gnu.org> ---
hmm.=20

__D.9984.3.4 means that this is a frame variable that is a 'promoted' tempo=
rary
(promoted because its lifetime had to be extended across a suspend point by
copying it into the frame).

So, I am supposing that this issue is because such a temporary would almost
certainly not have the same DECL_UID (from which the __D.xxxx is created) in
different TUs.

Which seems to imply that we need to find a way to disambiguate the frame
variable names for LTO.  This is, I would expect, another case of something
with local visibility becoming globally visible for LTO (but that's
supposition, not analysed).

the coros testsuite runs torture tests thus:
....
PASS: g++.dg/coroutines/torture/alloc-00-gro-on-alloc-fail.C   -O2 -flto
-flto-partition=3Dnone  (test for excess errors)
PASS: g++.dg/coroutines/torture/alloc-00-gro-on-alloc-fail.C   -O2 -flto
-flto-partition=3Dnone  execution test
PASS: g++.dg/coroutines/torture/alloc-00-gro-on-alloc-fail.C   -O2 -flto  (=
test
for excess errors)
PASS: g++.dg/coroutines/torture/alloc-00-gro-on-alloc-fail.C   -O2 -flto=20
execution test

so there is some coverage of LTO - but not multiple TUs :(.=