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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107561] [13 Regression] g++.dg/pr71488.C  and
 [g++.dg/warn/Warray-bounds-16.C -m32] regression due to -Wstringop-overflow
 problem
Date: Wed, 01 Mar 2023 14:34:38 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107561

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #16 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #15)
> The compiler doesn't know that the allocation function cannot clobber *th=
is.
> The C++ frontend tries to communicate this by making 'this' restrict
> qualified
> and we make use of that info, but for calls we do not know how to use the
> info.
>=20
> Maybe we can special-case directly the actual parameter case and compute
> the restrictness info for the call arguments.  The canonical example is
>=20
> void bar (void);
> struct X {
>   X (int);
>   int i;
>   int j;
> };
>=20
> X::X(int k)
> {
>   i =3D k;
>   bar ();
>   j =3D i !=3D k;
> }
>=20
> where if I understand you correctly, bar () is not allowed to modify *this
> (unless I pass it an argument to it, of course), even if *this is for
> example

Why?  Because it is a constructor and the object isn't fully constructed ye=
t at
that point?  For normal methods I certainly don't see anything that would
preclude such modifications.=