[Bug middle-end/109031] csmith: possible bad code with -O2 -fno-strict-aliasing

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109031

--- Comment #10 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to David Binderman from comment #9)
> (In reply to Martin Liška 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.
> > 
> > You can take an inspiration here:
> > https://github.com/marxin/gcc-util/blob/master/bisect/reduce.sh
> 
> Thanks for that. I am a bit further forward and I have this cvise
> script:
> 
> /usr/bin/gcc -w -Werror=implicit bug892.c -o one.exe
> 	&& (./one.exe 1 | fgrep "checksum after hashing g_50 :" > 1) 
> 	&& /home/dcb36/gcc/results/bin/gcc -w -O2 -fno-strict-aliasing bug892.c 
>  -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 want I
guess.

What about:

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

        if test $? != 0; then 
                exit 1

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

?

> 	&& (./two.exe 1 | fgrep "checksum after hashing g_50 :" > 2) 
> 	&& diff 1 2; 
> 	if test $? = 0; then 
> 		exit 1
> 	fi
> 		exit 0
> 
> 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.