Fix crash on serializing default-constructed QTimeZone

The serialization code neglected to check against null.  Sinze zones
are saved either by IANA ID or in our special OffsetFromUtc format,
representing an invalid zone by a string that cannot possibly be a
valid IANA ID will do.

Fixes: QTBUG-86019
Change-Id: I6882026403d00f8b254aab34c645f1cf8f9fcc2d
Reviewed-by: Taylor Braun-Jones <taylor@braun-jones.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 14f3f419b0864944d75283a850dc0ce141feaf0e)

1 files changed, 11 insertions, 2 deletions

diff --git a/src/corelib/tools/qtimezone.cpp b/src/corelib/tools/qtimezone.cpp
index cbc6b50c98..e0ce5dcd0d 100644
--- a/src/corelib/tools/qtimezone.cpp
+++ b/src/corelib/tools/qtimezone.cpp
@@ -1,5 +1,6 @@
 /****************************************************************************
 **
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Copyright (C) 2013 John Layt <jlayt@kde.org>
 ** Contact: https://www.qt.io/licensing/
 **
@@ -953,9 +954,15 @@ QList<QByteArray> QTimeZone::windowsIdToIanaIds(const QByteArray &windowsId,
 }
 
 #ifndef QT_NO_DATASTREAM
+// Invalid, as an IANA ID: too long, starts with - and has other invalid characters in it
+static inline QString invalidId() { return QStringLiteral("-No Time Zone Specified!"); }
+
 QDataStream &operator<<(QDataStream &ds, const QTimeZone &tz)
 {
-    tz.d->serialize(ds);
+    if (tz.isValid())
+        tz.d->serialize(ds);
+    else
+        ds << invalidId();
     return ds;
 }
 
@@ -963,7 +970,9 @@ QDataStream &operator>>(QDataStream &ds, QTimeZone &tz)
 {
     QString ianaId;
     ds >> ianaId;
-    if (ianaId == QLatin1String("OffsetFromUtc")) {
+    if (ianaId == invalidId()) {
+        tz = QTimeZone();
+    } else if (ianaId == QLatin1String("OffsetFromUtc")) {
         int utcOffset;
         QString name;
         QString abbreviation;