Bug 1076794 - tzset(3) and other time.h functions incorrectly set tzname[1] DST time zone name
Summary: tzset(3) and other time.h functions incorrectly set tzname[1] DST time zone name
Status: CLOSED DUPLICATE of bug 1077377
Alias: None
Product: Fedora
Classification: Fedora
Component: glibc
Version: 22
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Carlos O'Donell
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2014-03-15 08:39 UTC by pjp
Modified: 2016-02-05 15:12 UTC (History)
6 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2016-02-05 15:12:38 UTC
Type: Bug

Attachments (Terms of Use)
Reproducer for this bug. (972 bytes, text/x-c)
2014-03-15 08:39 UTC, pjp
no flags Details

Description pjp 2014-03-15 08:39:52 UTC
Created attachment 874734 [details]
Reproducer for this bug.

Description of problem:

"... The array tzname contains two strings, which are the standard names of the pair of time zones (standard and Daylight Saving) that the user has selected. tzname[0] is the name of the standard time zone (for example, "EST"), and tzname[1] is the name for the time zone when Daylight Saving Time is in use (for example, "EDT"). These correspond to the std and dst strings (respectively) from the TZ environment variable. If Daylight Saving Time is never used, tzname[1] is the empty string." [1]

As per the description above tzname[1] entry must be empty when DST is not used, ie. daylight=0. But instead it is set to the standard time zone, same as tzname[0]. It is problematic if a user has to set the TZ variable to: <tzname[0]><[+-]timezone><tzname[1]>, say


This definition is valid because EST does follow daylight saving time. But 


is an invalid definition, which affects working of other time.h functions like localtime(3), ctime(3) etc.

Version-Release number of selected component (if applicable): glibc-2.17-20.fc19.x86_64

How reproducible: Always

Steps to Reproduce:
1. $ download the attached reproducer
2. $ cc -xc -o dst dst.c
3. $ ./dst

Actual results:
  tz[0]: GMT, tz[1]: GMT
  timezone: 0, daylight: 0

  call tzset()

  tz[0]: IST, tz[1]: IST
  timezone: -5:30, daylight: 0

Expected results:
  tz[0]: GMT, tz[1]:
  timezone: 0, daylight: 0

  call tzset()

  tz[0]: IST, tz[1]:
  timezone: -5:30, daylight: 0

Additional info:
[1] https://www.gnu.org/software/libc/manual/html_node/Time-Zone-Functions.html#index-tzname-2716

Comment 1 Jaroslav Reznik 2015-03-03 15:34:52 UTC
This bug appears to have been reported against 'rawhide' during the Fedora 22 development cycle.
Changing version to '22'.

More information and reason for this action is here:

Comment 2 Florian Weimer 2016-02-05 15:12:38 UTC
IST used Daylight Saving Time during World War II, and this is reflected in tzdata.  This means the reproducer is not a counterexample to the specification you quoted.

*** This bug has been marked as a duplicate of bug 1077377 ***

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