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* [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization
@ 2006-02-08 10:57 egmont at uhulinux dot hu
2006-02-08 10:58 ` [Bug c/26172] " egmont at uhulinux dot hu
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: egmont at uhulinux dot hu @ 2006-02-08 10:57 UTC (permalink / raw)
To: gcc-bugs
Take
ftp://ftp.kernel.org/pub/linux/libs/pam/pre/library/Linux-PAM-0.99.3.0.tar.gz
compile it with
export CFLAGS="-fPIC -march=i586 -mtune=i586"
./configure [args...]; make
The resulted pam_lastlog.so module is wrong, there's an off-by-8-bytes bug
during a strncpy. However, if -O2 is also included amongst the CFLAGS, the
generated code is okay.
I attach the pam_lastlog.c file with two debug fprintf's inserted as well as
preprocessed source. The miscompiled part of the source is at line 278:
fprintf(stderr, "tl = %s\n", terminal_line); /* GCC BUG BELOW THIS LINE */
strncat(last_login.ll_line, terminal_line, sizeof(last_login.ll_line)-1);
fprintf(stderr, "ll = %s\n", last_login.ll_line); /* GCC BUG ABOVE THIS LINE */
Without -O2, the following is printed to stderr during a "su -":
tl = pts/2
ll = ?@????P*pts/2
^^^^^^^^ this is 8 bytes of binary garbage, always different.
With -O2, strncat copies the string as expected:
tl = pts/2
ll = pts/2
The gcc command line:
i586-uhu-linux-gcc -DHAVE_CONFIG_H -I. -I. -I../.. -I../../libpam/include
-I../../libpamc/include -fPIC -march=i586 -mtune=i586 -DPAM_DYNAMIC -W -Wall
-Wbad-function-cast -Wcast-align -Wcast-qual -Wmissing-declarations
-Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wstrict-prototypes
-Wwrite-strings -Winline -Wshadow -MT pam_lastlog.lo -MD -MP -MF
.deps/pam_lastlog.Tpo -c pam_lastlog.c -fPIC -DPIC -o .libs/pam_lastlog.o
--
Summary: generates wrong code for pam_lastlog w/o optimization
Product: gcc
Version: 3.4.5
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: egmont at uhulinux dot hu
GCC build triplet: i586-uhu-linux
GCC host triplet: i586-uhu-linux
GCC target triplet: i586-uhu-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/26172] generates wrong code for pam_lastlog w/o optimization
2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
@ 2006-02-08 10:58 ` egmont at uhulinux dot hu
2006-02-08 10:58 ` egmont at uhulinux dot hu
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: egmont at uhulinux dot hu @ 2006-02-08 10:58 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from egmont at uhulinux dot hu 2006-02-08 10:58 -------
Created an attachment (id=10800)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10800&action=view)
pam_lastlog.c with two extra fprintf's inserted (search for "GCC BUG" to find
them)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/26172] generates wrong code for pam_lastlog w/o optimization
2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
2006-02-08 10:58 ` [Bug c/26172] " egmont at uhulinux dot hu
@ 2006-02-08 10:58 ` egmont at uhulinux dot hu
2006-02-08 11:03 ` egmont at uhulinux dot hu
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: egmont at uhulinux dot hu @ 2006-02-08 10:58 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from egmont at uhulinux dot hu 2006-02-08 10:58 -------
Created an attachment (id=10801)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10801&action=view)
preproecessed source
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/26172] generates wrong code for pam_lastlog w/o optimization
2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
2006-02-08 10:58 ` [Bug c/26172] " egmont at uhulinux dot hu
2006-02-08 10:58 ` egmont at uhulinux dot hu
@ 2006-02-08 11:03 ` egmont at uhulinux dot hu
2006-02-08 11:07 ` rguenth at gcc dot gnu dot org
2006-02-08 11:21 ` egmont at uhulinux dot hu
4 siblings, 0 replies; 6+ messages in thread
From: egmont at uhulinux dot hu @ 2006-02-08 11:03 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from egmont at uhulinux dot hu 2006-02-08 11:03 -------
sorry, there's a typo. s/strncpy/strncat/
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/26172] generates wrong code for pam_lastlog w/o optimization
2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
` (2 preceding siblings ...)
2006-02-08 11:03 ` egmont at uhulinux dot hu
@ 2006-02-08 11:07 ` rguenth at gcc dot gnu dot org
2006-02-08 11:21 ` egmont at uhulinux dot hu
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2006-02-08 11:07 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from rguenth at gcc dot gnu dot org 2006-02-08 11:07 -------
/* copy to last_login */
last_login.ll_host[0] = '\0';
^^^^^^^^^
this should probably be ll_line. You'll just get uninitialized stack garbage
at -O0.
fprintf(stderr, "tl = %s\n", terminal_line); /* GCC BUG BELOW THIS LINE */
strncat(last_login.ll_line, terminal_line, sizeof(last_login.ll_line)-1);
fprintf(stderr, "ll = %s\n", last_login.ll_line); /* GCC BUG ABOVE THIS LINE */
terminal_line = NULL;
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution| |INVALID
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c/26172] generates wrong code for pam_lastlog w/o optimization
2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
` (3 preceding siblings ...)
2006-02-08 11:07 ` rguenth at gcc dot gnu dot org
@ 2006-02-08 11:21 ` egmont at uhulinux dot hu
4 siblings, 0 replies; 6+ messages in thread
From: egmont at uhulinux dot hu @ 2006-02-08 11:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from egmont at uhulinux dot hu 2006-02-08 11:21 -------
Shame on me... I spent some hours debugging the problem but didn't realize
that I'm always continuously mixing strcpy and strcat, I just thought the
other one was used there. You're perfectly right, thanks very much and sorry
for bothering you! I'll go and report it to the pam folks...
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26172
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2006-02-08 11:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2006-02-08 10:57 [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization egmont at uhulinux dot hu
2006-02-08 10:58 ` [Bug c/26172] " egmont at uhulinux dot hu
2006-02-08 10:58 ` egmont at uhulinux dot hu
2006-02-08 11:03 ` egmont at uhulinux dot hu
2006-02-08 11:07 ` rguenth at gcc dot gnu dot org
2006-02-08 11:21 ` egmont at uhulinux dot hu
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