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From: "gabravier at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/107115] Wrong codegen from TBAA under stores that
 change effective type?
Date: Tue, 27 Dec 2022 22:19:12 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107115

Gabriel Ravier <gabravier at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |gabravier at gmail dot com

--- Comment #13 from Gabriel Ravier <gabravier at gmail dot com> ---
Idk if it qualifies as the same bug or if this will prove to bee particular=
ly
useful, but just to make sure the corresponding issue in C++, triggered by =
this
slightly altered code (so that it hopefully respects the stricter rules C++=
 has
w.r.t. implicit object creation) which also fails to execute correctly on G=
CC,
is fixed by the fix to this issue, I'll post here the corresponding code:

#include <new>
#include <stdio.h>
#include <stdlib.h>

void test1(long *p1)
{
    p1 =3D (long *)new ((char*)p1) char[sizeof(long)];
    p1[0] =3D 1;
}

long test2(long long *p2, int index1, int index2)
{
    p2 =3D (long long *)new ((char*)p2) char[sizeof(long long)];
    p2[index1] =3D 2;
    return p2[index2];
}

long test3(long *p3, int index2, long value)
{
    p3 =3D (long *)new ((char*)p3) char[sizeof(long)];
    p3[index2] =3D 3;
    p3[index2] =3D value;
    return p3[0];
}

long test4(void *p4, int index1, int index2)
{
    test1((long *)p4);
    long temp =3D test2((long long *)p4, index1, index2);
    return test3((long *)p4, index2, temp);
}

long (*volatile vtest)(void *, int, int) =3D test4;

int main(void)
{
    void *pp =3D malloc(sizeof(long long));
    if (!pp) abort();
    long result =3D vtest(pp, 0, 0);
    printf("%lu/%lu\n", *std::launder((long *)pp), result);
}=