gcc-2.95.2-51 is buggy

Maybe I have to be more precise in the statement "gcc 2.95.2 is buggy".

I just installed gcc 2.95.2 freshly ftp'ed from ftp.gnu.org, and

% /usr/bin/gcc -v
Reading specs from /usr/lib/gcc-lib/i486-suse-linux/2.95.2/specs gcc version 2.95.2 19991024 (release)
% /usr/bin/gcc -Wall -O2 -o bug bug.c; ./bug
0x84800000
% /usr/gcc/aeb/bin/gcc -v
Reading specs from /usr/gcc/aeb/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/specs gcc version 2.95.2 19991024 (release)
% /usr/gcc/aeb/bin/gcc -Wall -O2 -o nobug bug.c; ./nobug
0x0

So, not all versions of gcc 2.95.2 are equal.

% rpm -qf /usr/bin/gcc
gcc-2.95.2-51

This is from a SuSE distribution, I forget which, not very recent. Revised summary: gcc-2.95.2-51 from SuSE is buggy.

Andries
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Interesting. Plain vanilla 2.95.2 from ftp.gnu.org exhibits the same bug on an BSDI2.1 i386 system.

defiant ~/tmp$ gcc -v
Reading specs from /usr/local/gnu/lib/gcc-lib/i386-pc-bsdi2.1/2.95.2/specs gcc version 2.95.2 19991024 (release)
defiant ~/tmp$ gcc -O2 -o bug bug.c; ./bug
0x4800000

Ion

  It is better to keep your mouth shut and be thought a fool,
            than to open it and remove all doubt.
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/usr/gcc/aeb/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/specs

Don't know if anyone else has noticed this but from what I've seen
posted it appears, unless I missed something, the gcc 2.95.2s that have exibited the bug were compiled for a 386 or a 486 while the one on which it worked was a 686. Perhaps the bug only appears on certain gcc configurations. Either the build configuration or the default optimization method(s), if I remember correctly gcc optimizes for the platform (i.e. i386, i486, i586, etc) it was configured for by default.

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I believe all 2.95.2's are equal in this, I think the fact that it gives 0 in the nobug case is some other reason:

$ for i in gcc kgcc '/usr/src/gcc-trunk/obj/gcc/xgcc -B /usr/src/gcc-trunk/obj/gcc/' '/usr/src/gcc-2.95.2/obj/gcc/xgcc -B /usr/src/gcc-2.95.2/obj/gcc/'; do $i -v; for j in -mcpu=i386 -mcpu=i586 -mcpu=i686; do $i $j -O2 -o aeb aeb.c; echo -n "$i $j "; ./aeb; done; done
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.0)
gcc -mcpu=i386 0x0
gcc -mcpu=i586 0x0
gcc -mcpu=i686 0x0
Reading specs from /usr/lib/gcc-lib/i386-glibc21-linux/egcs-2.91.66/specs
gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
kgcc -mcpu=i386 0x0
kgcc -mcpu=i586 0x0
kgcc -mcpu=i686 0x0
Reading specs from /usr/src/gcc-trunk/obj/gcc/specs
Configured with:
gcc version 2.97 20001120 (experimental)
/usr/src/gcc-trunk/obj/gcc/xgcc -B /usr/src/gcc-trunk/obj/gcc/ -mcpu=i386 0x0
/usr/src/gcc-trunk/obj/gcc/xgcc -B /usr/src/gcc-trunk/obj/gcc/ -mcpu=i586 0x0
/usr/src/gcc-trunk/obj/gcc/xgcc -B /usr/src/gcc-trunk/obj/gcc/ -mcpu=i686 0x0
Reading specs from /usr/src/gcc-2.95.2/obj/gcc/specs
gcc version 2.95.2 19991024 (release)
/usr/src/gcc-2.95.2/obj/gcc/xgcc -B /usr/src/gcc-2.95.2/obj/gcc/ -mcpu=i386 0x84800000
/usr/src/gcc-2.95.2/obj/gcc/xgcc -B /usr/src/gcc-2.95.2/obj/gcc/ -mcpu=i586 0x84800000
/usr/src/gcc-2.95.2/obj/gcc/xgcc -B /usr/src/gcc-2.95.2/obj/gcc/ -mcpu=i686 0x0

so the reason why it did not show up in the gcc you picked up from ftp.gnu.org is that you have compiled it so that it defaults to -mcpu=i686 where the bug does not show up.

Jakub
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