Make the named QColorSpace constructor thread-safe

Avoid accessing the shared pointer table without using atomic.

Cleans up the shared table on exit for leak tracking utilities.

Pick-to: 5.15
Change-Id: Ia2d6d79dea1c8be02bae2d8111e290f49eedf409
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

1 files changed, 24 insertions, 5 deletions

diff --git a/src/gui/painting/qcolorspace.cpp b/src/gui/painting/qcolorspace.cpp
index 5ae071f480..5657a90b9b 100644
--- a/src/gui/painting/qcolorspace.cpp
+++ b/src/gui/painting/qcolorspace.cpp
@@ -46,6 +46,7 @@
 #include "qcolortransform_p.h"
 #include "qicc_p.h"
 
+#include <qatomic.h>
 #include <qmath.h>
 #include <qtransform.h>
 
@@ -55,6 +56,18 @@ QT_BEGIN_NAMESPACE
 
 QBasicMutex QColorSpacePrivate::s_lutWriteLock;
 
+static QAtomicPointer<QColorSpacePrivate> s_predefinedColorspacePrivates[QColorSpace::ProPhotoRgb] = {};
+static void cleanupPredefinedColorspaces()
+{
+    for (QAtomicPointer<QColorSpacePrivate> &ptr : s_predefinedColorspacePrivates) {
+        QColorSpacePrivate *prv = ptr.fetchAndStoreAcquire(nullptr);
+        if (prv && !prv->ref.deref())
+            delete prv;
+    }
+}
+
+Q_DESTRUCTOR_FUNCTION(cleanupPredefinedColorspaces)
+
 QColorSpacePrimaries::QColorSpacePrimaries(QColorSpace::Primaries primaries)
 {
     switch (primaries) {
@@ -426,12 +439,18 @@ QColorSpace::QColorSpace(NamedColorSpace namedColorSpace)
         qWarning() << "QColorSpace attempted constructed from invalid QColorSpace::NamedColorSpace: " << int(namedColorSpace);
         return;
     }
-    static QColorSpacePrivate *predefinedColorspacePrivates[QColorSpace::ProPhotoRgb + 1];
-    if (!predefinedColorspacePrivates[namedColorSpace]) {
-        predefinedColorspacePrivates[namedColorSpace] = new QColorSpacePrivate(namedColorSpace);
-        predefinedColorspacePrivates[namedColorSpace]->ref.ref();
+    // The defined namespaces start at 1:
+    auto &atomicRef = s_predefinedColorspacePrivates[static_cast<int>(namedColorSpace) - 1];
+    QColorSpacePrivate *cspriv = atomicRef.loadAcquire();
+    if (!cspriv) {
+        auto *tmp = new QColorSpacePrivate(namedColorSpace);
+        tmp->ref.ref();
+        if (atomicRef.testAndSetOrdered(nullptr, tmp, cspriv))
+            cspriv = tmp;
+        else
+            delete tmp;
     }
-    d_ptr = predefinedColorspacePrivates[namedColorSpace];
+    d_ptr = cspriv;
     d_ptr->ref.ref();
     Q_ASSERT(isValid());
 }