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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/113599] [14 Regression] Wrong computation of member offset
 through pointer-to-member since r14-5503
Date: Thu, 25 Jan 2024 23:09:17 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113599

--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:fd620bd3351c6b9821c299035ed17e655d7954b5

commit r14-8439-gfd620bd3351c6b9821c299035ed17e655d7954b5
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Jan 26 00:08:36 2024 +0100

    c++: Fix up build_m_component_ref [PR113599]

    The following testcase reduced from GDB is miscompiled starting with
    r14-5503 PR112427 change.
    The problem is in the build_m_component_ref hunk, which changed
    -      datum =3D fold_build_pointer_plus (fold_convert (ptype, datum),
component);
    +      datum =3D cp_convert (ptype, datum, complain);
    +      if (!processing_template_decl)
    +       datum =3D build2 (POINTER_PLUS_EXPR, ptype,
    +                       datum, convert_to_ptrofftype (component));
    +      datum =3D cp_fully_fold (datum);
    Component is e, (sizetype) e is 16, offset of c inside of C.
    ptype is A *, pointer to type of C::c and datum is &d.
    Now, previously the above created ((A *) &d) p+ (sizetype) e which is
correct,
    but in the new code cp_convert sees that C has A as base class and
    instead of returning (A *) &d, it returns &d.D.2800 where D.2800 is
    the FIELD_DECL for the A base at offset 8 into C.
    So, instead of computing ((A *) &d) p+ (sizetype) e it computes
    &d.D.2800 p+ (sizetype) e, which is ((A *) &d) p+ 24.

    The following patch fixes it by using convert instead of cp_convert whi=
ch
    eventually calls build_nop (ptype, datum).

    2024-01-26  Jakub Jelinek  <jakub@redhat.com>

            PR c++/113599
            * typeck2.cc (build_m_component_ref): Use convert instead of
            cp_convert for pointer conversion.

            * g++.dg/expr/ptrmem11.C: New test.=