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* [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info @ 2011-11-11 0:08 pitrou at free dot fr 2011-11-11 11:36 ` [Bug libc/13401] " rosslagerwall at gmail dot com ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: pitrou at free dot fr @ 2011-11-11 0:08 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13401 Bug #: 13401 Summary: calling localtime() or mktime() with a time far in the past corrupts cached timezone info Product: glibc Version: 2.12 Status: NEW Severity: normal Priority: P2 Component: libc AssignedTo: drepper.fsp@gmail.com ReportedBy: pitrou@free.fr Classification: Unclassified See the following snippet: #include <time.h> #include <stdlib.h> int main() { time_t t; struct tm tmp; char str[200]; t = time(NULL); tmp = *gmtime(&t); tmp.tm_gmtoff = 0; tmp.tm_zone = NULL; strftime(str, sizeof(str), "%Z", &tmp); puts(str); t = -2461446500; localtime(&t); t = time(NULL); tmp = *gmtime(&t); tmp.tm_gmtoff = 0; tmp.tm_zone = NULL; strftime(str, sizeof(str), "%Z", &tmp); puts(str); return 0; } Output here is: CET PMT After a bit of digging, it seems the external variable "tzname" gets (wrongly) mutated by the localtime() call. The "%Z" format specifier just reuses that info. This issue got reproduced on several distributions, see http://bugs.python.org/issue13309 -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libc/13401] calling localtime() or mktime() with a time far in the past corrupts cached timezone info 2011-11-11 0:08 [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info pitrou at free dot fr @ 2011-11-11 11:36 ` rosslagerwall at gmail dot com 2011-11-21 13:11 ` schwab@linux-m68k.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: rosslagerwall at gmail dot com @ 2011-11-11 11:36 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13401 Ross Lagerwall <rosslagerwall at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rosslagerwall at gmail dot | |com -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libc/13401] calling localtime() or mktime() with a time far in the past corrupts cached timezone info 2011-11-11 0:08 [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info pitrou at free dot fr 2011-11-11 11:36 ` [Bug libc/13401] " rosslagerwall at gmail dot com @ 2011-11-21 13:11 ` schwab@linux-m68k.org 2011-11-21 15:02 ` pitrou at free dot fr 2014-06-27 11:37 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: schwab@linux-m68k.org @ 2011-11-21 13:11 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13401 Andreas Schwab <schwab@linux-m68k.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |INVALID --- Comment #1 from Andreas Schwab <schwab@linux-m68k.org> 2011-11-21 13:09:49 UTC --- By overwriting tm_gmtoff and tm_zone the struct tm is no longer valid. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libc/13401] calling localtime() or mktime() with a time far in the past corrupts cached timezone info 2011-11-11 0:08 [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info pitrou at free dot fr 2011-11-11 11:36 ` [Bug libc/13401] " rosslagerwall at gmail dot com 2011-11-21 13:11 ` schwab@linux-m68k.org @ 2011-11-21 15:02 ` pitrou at free dot fr 2014-06-27 11:37 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: pitrou at free dot fr @ 2011-11-21 15:02 UTC (permalink / raw) To: glibc-bugs http://sourceware.org/bugzilla/show_bug.cgi?id=13401 --- Comment #2 from Antoine Pitrou <pitrou at free dot fr> 2011-11-21 15:00:13 UTC --- These fields are "overwritten" by hand in the example for ease of reproduction. The actual use case is to fill the members of a struct tm by hand from user data. Since tm_gmtoff and tm_zone are not specified by POSIX, they are left alone, zero-filled (the struct is previously initialized with memset()). There's no portable way that I know of to initialize these fields. While the most basic use of strftime() indeed consists in formatting a struct tm returned by a libc function (such as gmtime()), it seems reasonable to use strftime() to format user-defined time data. Nowhere does POSIX seem to say that the struct tm *has* to come from gmtime() or similar functions. -- Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug libc/13401] calling localtime() or mktime() with a time far in the past corrupts cached timezone info 2011-11-11 0:08 [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info pitrou at free dot fr ` (2 preceding siblings ...) 2011-11-21 15:02 ` pitrou at free dot fr @ 2014-06-27 11:37 ` fweimer at redhat dot com 3 siblings, 0 replies; 5+ messages in thread From: fweimer at redhat dot com @ 2014-06-27 11:37 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=13401 Florian Weimer <fweimer at redhat dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Flags| |security- -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-06-27 11:37 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2011-11-11 0:08 [Bug libc/13401] New: calling localtime() or mktime() with a time far in the past corrupts cached timezone info pitrou at free dot fr 2011-11-11 11:36 ` [Bug libc/13401] " rosslagerwall at gmail dot com 2011-11-21 13:11 ` schwab@linux-m68k.org 2011-11-21 15:02 ` pitrou at free dot fr 2014-06-27 11:37 ` fweimer at redhat dot com
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