Revert "QMutexPool: avoid QVarLengthArray of QAtomicPointers"

This reverts commit 4579d966af2e5d4ba229f13312eeb2f921406038.

This causes a miscompilation with ICC 16 on Windows (MSVC 2015 ABI): the
vector created by new[] with () in:

      mutexes(new QAtomicPointer<QMutex>[size]()), // (): zero-initialize

does not actually zero-initialize (see disassembly in the bug
report). This is definitely a compiler bug.

Since we plan on removing QMutexPool in Qt 5.8 anyway, let's just revert
the patch.

Task-number: QTBUG-53360
Change-Id: I06bae9392f534e45b3f1ffff144e823b747e7962
Reviewed-by: Kai Koehne <kai.koehne@qt.io>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/corelib/thread/qmutexpool.cpp b/src/corelib/thread/qmutexpool.cpp
index 522fd5eac2..90b6989467 100644
--- a/src/corelib/thread/qmutexpool.cpp
+++ b/src/corelib/thread/qmutexpool.cpp
@@ -92,10 +92,11 @@ Q_GLOBAL_STATIC_WITH_ARGS(QMutexPool, globalMutexPool, (QMutex::Recursive))
     QMutexPool is destructed.
 */
 QMutexPool::QMutexPool(QMutex::RecursionMode recursionMode, int size)
-    : count(size),
-      mutexes(new QAtomicPointer<QMutex>[size]()), // (): zero-initialize
-      recursionMode(recursionMode)
+    : mutexes(size), recursionMode(recursionMode)
 {
+    for (int index = 0; index < mutexes.count(); ++index) {
+        mutexes[index].store(0);
+    }
 }
 
 /*!
@@ -104,8 +105,8 @@ QMutexPool::QMutexPool(QMutex::RecursionMode recursionMode, int size)
 */
 QMutexPool::~QMutexPool()
 {
-    qDeleteAll(mutexes, mutexes + count);
-    delete[] mutexes;
+    for (int index = 0; index < mutexes.count(); ++index)
+        delete mutexes[index].load();
 }
 
 /*!