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LibC+LibCore: Use tm_isdst to handle time zone offsets in DST

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Previously, we were incorrectly assuming that the daylight global
variable indicated whether the current time zone is in DST. In reality,
the daylight variable only indicates whether a time zone *can* be in
DST.

Instead, the tm structure has a tm_isdst member that should be used for
this purpose. Ensure our LibC handles tm_isdst, and avoid errant usage
of the daylight variable in Core::DateTime.
This commit is contained in:
Timothy Flynn 2022-08-02 08:42:58 -04:00 • committed by Linus Groh
parent e683ca00cc
commit a4a7efaf5f
2 changed files with 30 additions and 21 deletions
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20
Userland/Libraries/LibCore/DateTime.cpp
View file

@ -92,13 +92,13 @@ String DateTime::to_string(StringView format) const
int const format_len = format.length();
auto format_time_zone_offset = [&](bool with_separator) {
#if defined(__serenity__)
auto offset_seconds = daylight ? -altzone : -timezone;
#elif !defined(__FreeBSD__)
auto offset_seconds = -timezone;
#else
auto offset_seconds = 0;
#endif
struct tm gmt_tm;
gmtime_r(&m_timestamp, &gmt_tm);
gmt_tm.tm_isdst = -1;
auto gmt_timestamp = mktime(&gmt_tm);
auto offset_seconds = static_cast<time_t>(difftime(m_timestamp, gmt_timestamp));
StringView offset_sign;
if (offset_seconds >= 0) {
@ -251,11 +251,7 @@ String DateTime::to_string(StringView format) const
format_time_zone_offset(true);
break;
case 'Z': {
#ifndef __FreeBSD__
auto const* timezone_name = tzname[daylight];
#else
auto const* timezone_name = tzname[0];
#endif
auto const* timezone_name = tzname[tm.tm_isdst == 0 ? 0 : 1];
builder.append({ timezone_name, strlen(timezone_name) });
break;
}