Fixed qrand global static related problem.

qrand() uses global static seed storage, but if used
from destructors of other global static objects
(directly or via ~QSettings() or QMap::insert())
the global static seed storage can be already deleted.
Fallback to plain rand() in this case.

Task-number: QTBUG-5218
Reviewed-by: Justin McPherson

1 files changed, 40 insertions, 19 deletions

diff --git a/src/corelib/global/qglobal.cpp b/src/corelib/global/qglobal.cpp
index 7d47944..36e15b9 100644
--- a/src/corelib/global/qglobal.cpp
+++ b/src/corelib/global/qglobal.cpp
@@ -2513,10 +2513,19 @@ Q_GLOBAL_STATIC(SeedStorage, randTLS)  // Thread Local Storage for seed value
 void qsrand(uint seed)
 {
 #if defined(Q_OS_UNIX) && !defined(QT_NO_THREAD) && !defined(Q_OS_SYMBIAN)
-    SeedStorageType *pseed = randTLS()->localData();
-    if (!pseed)
-        randTLS()->setLocalData(pseed = new SeedStorageType);
-    *pseed = seed;
+    SeedStorage *seedStorage = randTLS();
+    if (seedStorage) {
+        SeedStorageType *pseed = seedStorage->localData();
+        if (!pseed)
+            seedStorage->setLocalData(pseed = new SeedStorageType);
+        *pseed = seed;
+    } else {
+        //golbal static seed storage should always exist,
+        //except after being deleted by QGlobalStaticDeleter.
+        //But since it still can be called from destructor of another
+        //global static object, fallback to sqrand(seed)
+        srand(seed);
+    }
 #else
     // On Windows srand() and rand() already use Thread-Local-Storage
     // to store the seed between calls
@@ -2536,17 +2545,20 @@ void qsrand(uint seed)
 void qsrand()
 {
 #if (defined(Q_OS_UNIX) || defined(Q_OS_WIN)) && !defined(QT_NO_THREAD) && !defined(Q_OS_SYMBIAN)
-    SeedStorageType *pseed = randTLS()->localData();
-    if (pseed) {
-        // already seeded
-        return;
+    SeedStorage *seedStorage = randTLS();
+    if (seedStorage) {
+        SeedStorageType *pseed = seedStorage->localData();
+        if (pseed) {
+            // already seeded
+            return;
+        }
+        seedStorage->setLocalData(pseed = new SeedStorageType);
+        // start beyond 1 to avoid the sequence reset
+        static QBasicAtomicInt serial = Q_BASIC_ATOMIC_INITIALIZER(2);
+        *pseed = QDateTime::currentDateTime().toTime_t()
+                 + quintptr(&pseed)
+                 + serial.fetchAndAddRelaxed(1);
     }
-    randTLS()->setLocalData(pseed = new SeedStorageType);
-    // start beyond 1 to avoid the sequence reset
-    static QBasicAtomicInt serial = Q_BASIC_ATOMIC_INITIALIZER(2);
-    *pseed = QDateTime::currentDateTime().toTime_t()
-             + quintptr(&pseed)
-             + serial.fetchAndAddRelaxed(1);
 #if defined(Q_OS_WIN)
     // for Windows the srand function must still be called.
     srand(*pseed);
@@ -2584,12 +2596,21 @@ void qsrand()
 int qrand()
 {
 #if defined(Q_OS_UNIX) && !defined(QT_NO_THREAD) && !defined(Q_OS_SYMBIAN)
-    SeedStorageType *pseed = randTLS()->localData();
-    if (!pseed) {
-        randTLS()->setLocalData(pseed = new SeedStorageType);
-        *pseed = 1;
+    SeedStorage *seedStorage = randTLS();
+    if (seedStorage) {
+        SeedStorageType *pseed = seedStorage->localData();
+        if (!pseed) {
+            seedStorage->setLocalData(pseed = new SeedStorageType);
+            *pseed = 1;
+        }
+        return rand_r(pseed);
+    } else {
+        //golbal static seed storage should always exist,
+        //except after being deleted by QGlobalStaticDeleter.
+        //But since it still can be called from destructor of another
+        //global static object, fallback to qrand()
+        return rand();
     }
-    return rand_r(pseed);
 #else
     // On Windows srand() and rand() already use Thread-Local-Storage
     // to store the seed between calls