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authorEdward Welbourne <edward.welbourne@qt.io>2017-10-27 16:40:46 +0200
committerEdward Welbourne <edward.welbourne@qt.io>2017-11-30 20:19:54 +0000
commita99c773972d845e453a86974653df19f60d8e7ca (patch)
treefa5d5d86f33d81a8c55b16a21638af37e0adaf5b /src/corelib/tools
parent81ad5bc838538084d14e4627ad405262026b72a2 (diff)
Refine handling of wMonth checks in QWinTimeZonePrivate
The MS API documents that the two TIME_ZONE_INFORMATION date fields either both have wMonth clear (when there is no DST) or both have it set (for each part of a DST pair). This rule is followed even when there's a standard time change without DST, with perverse results I'll deal with in a later commit. Add code in init() to verify the rule is followed and qWarning() if not. A year with no transitions doesn't imply no earlier or later year has transitions, so don't give up on searches for transitions because of it. Also fix a potential uninitialized variable bug, related to data() breaking out of a loop on such a year. Change-Id: I1ad86c07e54b2eb835a2e02d18dc64022f52a0d9 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Diffstat (limited to 'src/corelib/tools')
-rw-r--r--src/corelib/tools/qtimezoneprivate_win.cpp34
1 files changed, 28 insertions, 6 deletions
diff --git a/src/corelib/tools/qtimezoneprivate_win.cpp b/src/corelib/tools/qtimezoneprivate_win.cpp
index 3bce55925f..e9930f4fe6 100644
--- a/src/corelib/tools/qtimezoneprivate_win.cpp
+++ b/src/corelib/tools/qtimezoneprivate_win.cpp
@@ -491,6 +491,7 @@ void QWinTimeZonePrivate::init(const QByteArray &ianaId)
m_id = ianaId;
}
+ bool badMonth = false; // Only warn once per zone, if at all.
if (!m_windowsId.isEmpty()) {
#ifdef QT_USE_REGISTRY_TIMEZONE
// Open the base TZI for the time zone
@@ -518,6 +519,14 @@ void QWinTimeZonePrivate::init(const QByteArray &ianaId)
// Don't repeat a recurrent rule:
&& (m_tranRules.isEmpty()
|| !isSameRule(m_tranRules.last(), rule))) {
+ if (!badMonth
+ && (rule.standardTimeRule.wMonth == 0)
+ != (rule.daylightTimeRule.wMonth == 0)) {
+ badMonth = true;
+ qWarning("MS registry TZ API violated its wMonth constraint;"
+ "this may cause mistakes for %s from %d",
+ ianaId.constData(), year);
+ }
rule.startYear = m_tranRules.isEmpty() ? MIN_YEAR : year;
m_tranRules.append(rule);
}
@@ -553,6 +562,14 @@ void QWinTimeZonePrivate::init(const QByteArray &ianaId)
// Don't repeat a recurrent rule
&& (m_tranRules.isEmpty()
|| !isSameRule(m_tranRules.last(), rule))) {
+ if (!badMonth
+ && (rule.standardTimeRule.wMonth == 0)
+ != (rule.daylightTimeRule.wMonth == 0)) {
+ badMonth = true;
+ qWarning("MS dynamic TZ API violated its wMonth constraint;"
+ "this may cause mistakes for %s from %d",
+ ianaId.constData(), year);
+ }
rule.startYear = m_tranRules.isEmpty() ? MIN_YEAR : year;
m_tranRules.append(rule);
}
@@ -650,6 +667,7 @@ QTimeZonePrivate::Data QWinTimeZonePrivate::data(qint64 forMSecsSinceEpoch) cons
qint64 second;
qint64 next = maxMSecs();
TransitionTimePair pair;
+ Q_ASSERT(next != pair.dst); // so break on first iteration gets standard time
QWinTransitionRule rule;
do {
// Convert the transition rules into msecs for the year we want to try
@@ -712,9 +730,11 @@ QTimeZonePrivate::Data QWinTimeZonePrivate::nextTransition(qint64 afterMSecsSinc
do {
// Convert the transition rules into msecs for the year we want to try
rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
- // If no transition rules to calculate then no next transition
- if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0)
- return invalidData();
+ // If there's no transition this year, check for a later year:
+ if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0) {
+ ++year;
+ continue;
+ }
pair = TransitionTimePair(rule, year);
// Find the first and second transition for the year
if (pair.std < pair.dst) {
@@ -762,9 +782,11 @@ QTimeZonePrivate::Data QWinTimeZonePrivate::previousTransition(qint64 beforeMSec
do {
// Convert the transition rules into msecs for the year we want to try
rule = m_tranRules.at(ruleIndexForYear(m_tranRules, year));
- // If no transition rules to calculate then no previous transition
- if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0)
- return invalidData();
+ // If there's no transition this year, check for an earlier year:
+ if (rule.standardTimeRule.wMonth == 0 && rule.daylightTimeRule.wMonth == 0) {
+ --year;
+ continue;
+ }
pair = TransitionTimePair(rule, year);
if (pair.std < pair.dst) {
first = pair.std;