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From: "marxin at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/109031] csmith: possible bad code with -O2
 -fno-strict-aliasing
Date: Wed, 08 Mar 2023 13:43:03 +0000
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X-Bugzilla-Keywords: needs-bisection, needs-reduction, wrong-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109031

--- Comment #10 from Martin Li=C5=A1ka <marxin at gcc dot gnu.org> ---
(In reply to David Binderman from comment #9)
> (In reply to Martin Li=C5=A1ka from comment #8)
> > > but then if diff returns 1, the script should return 0 and
> > > if diff returns 0, then the script should return 1.
> >=20
> > You can take an inspiration here:
> > https://github.com/marxin/gcc-util/blob/master/bisect/reduce.sh
>=20
> Thanks for that. I am a bit further forward and I have this cvise
> script:
>=20
> /usr/bin/gcc -w -Werror=3Dimplicit bug892.c -o one.exe
> 	&& (./one.exe 1 | fgrep "checksum after hashing g_50 :" > 1)=20
> 	&& /home/dcb36/gcc/results/bin/gcc -w -O2 -fno-strict-aliasing bug892.c=
=20
>  -o two.exe

If the compilation fails for any reason, then the compound && expression is
false (non-zero) and thus you end up with 'exit 0'. That's not what you wan=
t I
guess.

What about:

/usr/bin/gcc -w -Werror=3Dimplicit bug892.c -o one.exe
        && (./one.exe 1 | fgrep "checksum after hashing g_50 :" > 1)=20
        && /home/dcb36/gcc/results/bin/gcc -w -O2 -fno-strict-aliasing bug8=
92.c=20
 -o two.exe
        && (./two.exe 1 | fgrep "checksum after hashing g_50 :" > 2)=20

        if test $? !=3D 0; then=20
                exit 1

        diff 1 2;=20
        if test $? =3D 0; then=20
                exit 1
        fi
                exit 0

?

> 	&& (./two.exe 1 | fgrep "checksum after hashing g_50 :" > 2)=20
> 	&& diff 1 2;=20
> 	if test $? =3D 0; then=20
> 		exit 1
> 	fi
> 		exit 0
>=20
> It still doesn't work right and I can't fathom what's wrong.
> It all works nicely when I do it line by line.=