Bug#12375: marked as done ([Fix in {gcc,egcc}-2.91.x] gcc: -O2 produces bad code !)
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and subject line closing gcc272 bugs
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Date: Fri, 29 Aug 1997 23:10:45 +0200
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From: Yann Dirson <dwitch@monge.univ-mlv.fr>
To: submit@bugs.debian.org
Subject: gcc: -O2 produces bad code !
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Package: gcc
Version: 2.7.2.2-5
This bug should probably be forwarded upstream.
-O2 optimization may cause erroneous code to be produced. Whether the bug
is triggered is highly context-dependant, and the included bug.c is near
minimal. The bug occurs on line 25 ("for..."); when suppressing lines
immediately preceding/following this one, the bug doesn't show.
What happens is that argv is incremented by 4, just as if "argv++" has
been written.
-O1 doesn't produce this behaviour, as demonstrated by the "showbug" script.
the bug was reproduced on 2 debian machines.
debian versions of software used:
gcc 2.7.2.1-2 2.7.2.2-5
libc5 5.4.33-3 N/A
libc6 N/A 2.0.4-1
binutils 2.7-3 2.8.1-1
ldso 1.8.5-1 1.9.2-1
Fortunately, it seems easy to reproduce
attached files are:
bug.c small C program influenced by the bug
.gdbinit gdb script running the program and displaying
influenced data
showbug sh script showing the bug
--
Yann Dirson <dirson@univ-mlv.fr>
alt-email:<ydirson@a2points.com>
http://monge.univ-mlv.fr/~dirson
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#include <errno.h>
#include <stdio.h>
#include <sys/kd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#define VERSION "1"
char *progname;
int verbose = 0;
int getfd() {
return 0;
}
int main(int argc, char *argv[])
{
int fd, i;
progname = argv[0];
fd = getfd();
for (i = 1; i < argc; i++)
{
if (!strcmp(argv[i], "-V"))
printf("%s version %s\n", progname, VERSION);
else if (!strcmp(argv[i], "-v"))
verbose = 1;
}
return 0;
}
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list 25
break 25
run an_arg
echo argv is:
print argv
next
echo argv is:
print argv
quit
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Content-Type: application/octet-stream
Content-Disposition: attachment; filename="showbug"
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#!/bin/sh
echo 'Compiling demos...'
gcc -g -O1 bug.c -o bugO1
gcc -g -O2 bug.c -o bugO2
echo 'Showing correct results (-O1)...'
gdb bugO1
echo 'Showing buggy results (-O2)...'
gdb bugO2
--Multipart_Fri_Aug_29_23:10:17_1997-1--
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Date: Thu, 12 Apr 2001 23:52:39 +0200 (MEST)
To: 4429-done@bugs.debian.org, 4430-done@bugs.debian.org,
4954-done@bugs.debian.org, 5367-done@bugs.debian.org,
6047-done@bugs.debian.org, 12375-done@bugs.debian.org,
20606-done@bugs.debian.org, 20889-done@bugs.debian.org,
24788-done@bugs.debian.org, 26100-done@bugs.debian.org,
34322-done@bugs.debian.org, 48726-done@bugs.debian.org,
54544-done@bugs.debian.org, 63154-done@bugs.debian.org
Subject: closing gcc272 bugs
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Delivered-To: 12375-done@bugs.debian.org
gcc272 (2.7.2.3-18) unstable; urgency=low
* Close all gcc272 in the Debian bug tracking archive. The use of
gcc272 is deprecated. The only reason it exists is to have a
compiler for the linux kernel 2.0.x.
The bug reports for gcc272 are still available on
http://bugs.debian.org/cgi-bin/pkgreport.cgi?pkg=gcc272&archive=yes
Closes: #4429, #4430, 4954, #5367, #6047, #12375, #20606, #20889,
#24788, #26100, #34322, #48726, #54544, #63154.
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