From ba19363529f4c099c6831c26d3acf98fa0c5f702 Mon Sep 17 00:00:00 2001
From: Edward Welbourne <edward.welbourne@qt.io>
Date: Thu, 4 May 2017 16:45:22 +0200
Subject: Mutex-lock QLocale's update of its globalLocaleData

For want of this, nothing that used QLocale::system(), inter alia,
could be thread-safe or re-entrant.

Task-number: QTBUG-49473
Change-Id: I3e017aa7d59c4c39828bb5cdc7ff0780ea66bafe
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/tools/qlocale.cpp | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

(limited to 'src')

diff --git a/src/corelib/tools/qlocale.cpp b/src/corelib/tools/qlocale.cpp
index 179784c7ba..06beabbee3 100644
--- a/src/corelib/tools/qlocale.cpp
+++ b/src/corelib/tools/qlocale.cpp
@@ -64,6 +64,9 @@
 #include "qstringbuilder.h"
 #include "private/qnumeric_p.h"
 #include <cmath>
+#ifndef QT_NO_SYSTEMLOCALE
+#   include "qmutex.h"
+#endif
 #ifdef Q_OS_WIN
 #   include <qt_windows.h>
 #   include <time.h>
@@ -593,8 +596,6 @@ static QLocalePrivate *c_private()
 }
 
 #ifndef QT_NO_SYSTEMLOCALE
-
-
 /******************************************************************************
 ** Default system locale behavior
 */
@@ -683,14 +684,24 @@ void QLocalePrivate::updateSystemPrivate()
     if (!res.isNull())
         system_data->m_plus = res.toString().at(0).unicode();
 }
-#endif
+#endif // !QT_NO_SYSTEMLOCALE
 
 static const QLocaleData *systemData()
 {
 #ifndef QT_NO_SYSTEMLOCALE
-    // copy over the information from the fallback locale and modify
-    if (!system_data || system_data->m_language_id == 0)
-        QLocalePrivate::updateSystemPrivate();
+    /*
+      Copy over the information from the fallback locale and modify.
+
+      This modifies (cross-thread) global state, so take care to only call it in
+      one thread.
+    */
+    {
+        static QBasicMutex systemDataMutex;
+        systemDataMutex.lock();
+        if (!system_data || system_data->m_language_id == 0)
+            QLocalePrivate::updateSystemPrivate();
+        systemDataMutex.unlock();
+    }
 
     return system_data;
 #else
-- 
cgit v1.2.3