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From: "joker.eph at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/109963] New: ABI: unexpected layout ordering of `this`
 pointer in lambda capture
Date: Thu, 25 May 2023 07:20:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109963

            Bug ID: 109963
           Summary: ABI: unexpected layout ordering of `this` pointer in
                    lambda capture
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joker.eph at gmail dot com
  Target Milestone: ---

See the discussion here: https://github.com/itanium-cxx-abi/cxx-abi/issues/=
141

Most recent post at the moment was calling out a possible implementation bu=
g in
GCC:

> If compilers aren't going to give lambdas internal linkage in these situa=
tions, the ABI needs to define a layout for them. As far as I can tell, Cla=
ng, GCC, and ICC are all trying to use the same layout rule: explicit captu=
res are added in declaration order, then implicit captures are added in the=
 source order of their ODR use in the lambda body. The exception which caus=
es this incompatibility is that GCC seems to order implicit this arguments =
(and only implicit ones) after the formal call arguments. I would argue tha=
t that's just a GCC bug, and the this argument should be ordered as if it w=
ere written in source. @jicama, do you agree?=