Add support for /etc/TZ as default value for $TZ

This is used by uClibc, at least.

[ChangeLog][QtCore][QTimeZone] The TZDB back-end now recognizes the
contents of /etc/TZ as a fall-back for $TZ (as used by uClibc).

Fixes: QTBUG-75565
Change-Id: I3067e2d023cf30a85633575b5d7dc0ee3ec36927
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/src/corelib/tools/qtimezoneprivate_tz.cpp b/src/corelib/tools/qtimezoneprivate_tz.cpp
index d9e87212d3..f5440799ab 100644
--- a/src/corelib/tools/qtimezoneprivate_tz.cpp
+++ b/src/corelib/tools/qtimezoneprivate_tz.cpp
@@ -659,7 +659,7 @@ void QTzTimeZonePrivate::init(const QByteArray &ianaId)
         if (!tzif.open(QIODevice::ReadOnly)) {
             tzif.setFileName(QLatin1String("/usr/lib/zoneinfo/") + QString::fromLocal8Bit(ianaId));
             if (!tzif.open(QIODevice::ReadOnly)) {
-                // ianaId may be a POSIX rule, taken from $TZ
+                // ianaId may be a POSIX rule, taken from $TZ or /etc/TZ
                 const QByteArray zoneInfo = ianaId.split(',').at(0);
                 const char *begin = zoneInfo.constBegin();
                 if (PosixZone::parse(begin, zoneInfo.constEnd()).hasValidOffset()
@@ -1114,6 +1114,13 @@ QByteArray QTzTimeZonePrivate::systemTimeZoneId() const
         }
     }
 
+    // Some systems (e.g. uClibc) have a default value for $TZ in /etc/TZ:
+    if (ianaId.isEmpty()) {
+        QFile zone(QStringLiteral("/etc/TZ"));
+        if (zone.open(QIODevice::ReadOnly))
+            ianaId = zone.readAll().trimmed();
+    }
+
     // Give up for now and return UTC
     if (ianaId.isEmpty())
         ianaId = utcQByteArray();