fix: account for DST in XCCDF result timestamp offset#2367
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The start-time/end-time attributes on XCCDF TestResult elements are produced by _get_timestamp(). On glibc the offset was taken from the global `timezone` variable, which holds the standard-time offset and does not account for daylight saving time. The wall-clock fields come from localtime_r() and are DST-correct, so during DST the printed offset was wrong by one hour, making the timestamp denote the wrong instant (e.g. an America/Los_Angeles scan in summer reported -08:00 instead of -07:00). Use struct tm.tm_gmtoff when available; it carries the actual UTC offset in effect at the represented local time, DST included. A new HAVE_STRUCT_TM_TM_GMTOFF CMake feature check guards it, falling back to the timezone global (plus a DST hour) on platforms without tm_gmtoff such as the MSVC runtime. This also drops the FreeBSD-specific branch that previously re-added an hour to deliberately mirror the glibc bug. Fixes OpenSCAP#1972 Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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Pull request overview
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This PR improves cross-platform timezone offset handling when generating timestamps by preferring struct tm.tm_gmtoff when available and adding a configure-time check for it.
Changes:
- Use
tm_gmtoff(when present) for UTC offset, including DST, instead of platform-specific conditionals. - Add a CMake compile-time probe and config macro (
HAVE_STRUCT_TM_TM_GMTOFF) to detecttm_gmtoff. - Refine fallback offset logic using the global
timezonevalue plus DST adjustment.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/XCCDF/result.c | Switches to tm_gmtoff when available; adjusts fallback timezone logic and comments. |
| config.h.in | Adds HAVE_STRUCT_TM_TM_GMTOFF config define. |
| CMakeLists.txt | Adds check_struct_has_member probe for struct tm.tm_gmtoff. |
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| /* Fallback for platforms without tm_gmtoff (e.g. the MSVC runtime). | ||
| * timezone is a global variable set by localtime(3) holding the offset | ||
| * of standard time; add an hour when daylight saving time is in effect. */ | ||
| long std_diff = timezone; | ||
| if (lt->tm_isdst > 0) | ||
| std_diff -= 3600; |
The fallback path subtracts 3600 seconds from `timezone`, but the comment described this as "add an hour", which reads as contradicting the code. Reword to explain that `timezone` is seconds west of UTC and DST shifts local time one hour east (closer to UTC), so the westward offset is reduced by 3600 seconds. No behavior change.
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Problem
oscapwritesstart-time/end-timeattributes on XCCDFTestResultelements via
_get_timestamp()insrc/XCCDF/result.c. On glibc the UTCoffset was derived from the global
timezonevariable, which holds thestandard-time offset and ignores daylight saving time. The wall-clock
fields (
tm_hour, ...) come fromlocaltime_r()and are DST-adjusted, soduring DST the offset and the time disagreed and the timestamp pointed to the
wrong instant — exactly the symptom in #1972 (an
America/Los_Angelesscan insummer emitted
-08:00instead of-07:00, an hour off).Fix
Use
struct tm.tm_gmtoffwhen the platform provides it.tm_gmtoffis theoffset east of UTC in seconds, already including DST, so it matches the actual
offset in effect at the represented local time.
HAVE_STRUCT_TM_TM_GMTOFFCMake feature check (check_struct_has_member).tm_gmtoff(e.g. the MSVC runtime) keep thetimezoneglobal path, now corrected to add an hour when
tm_isdst > 0.reproduce the glibc bug for consistency; FreeBSD now takes the correct
tm_gmtoffpath like glibc.Verification
A full project build was not possible in my environment (no
cmake/xmlsec1and no sudo), but I verified the change directly:
against libc's authoritative
strftime("%z")forAmerica/Los_Angeles,Europe/BerlinandUTC, in both summer and winter. Both thetm_gmtoffpath and the fallback path produce the correct offset in every case
(
-07:00/-08:00,+02:00/+01:00,+00:00).gcc -fsyntax-onlyon the editedresult.cagainstthe real project headers passes cleanly with
HAVE_STRUCT_TM_TM_GMTOFFdefined and undefined (both
#ifdefbranches).Fixes #1972