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From: "egmont at uhulinux dot hu" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/26172] New: generates wrong code for pam_lastlog w/o optimization Date: Wed, 08 Feb 2006 10:57:00 -0000 [thread overview] Message-ID: <bug-26172-12154@http.gcc.gnu.org/bugzilla/> (raw) 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
next reply other threads:[~2006-02-08 10:57 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2006-02-08 10:57 egmont at uhulinux dot hu [this message] 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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