1 files changed, 13 insertions, 30 deletions
diff --git a/src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm b/src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm
index 03148c769b..a94e0dc517 100644
--- a/src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm
+++ b/src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm
@@ -86,16 +86,21 @@
 
 QT_USE_NAMESPACE
 
-QT_BEGIN_NAMESPACE
-static QCocoaApplicationDelegate *sharedCocoaApplicationDelegate = nil;
+@implementation QCocoaApplicationDelegate
 
-static void cleanupCocoaApplicationDelegate()
++ (instancetype)sharedDelegate
 {
-    [sharedCocoaApplicationDelegate release];
+    static QCocoaApplicationDelegate *shared = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        shared = [[self alloc] init];
+        atexit_b(^{
+            [shared release];
+            shared = nil;
+        });
+    });
+    return shared;
 }
-QT_END_NAMESPACE
-
-@implementation QCocoaApplicationDelegate
 
 - (id)init
 {
@@ -120,7 +125,6 @@ QT_END_NAMESPACE
 
 - (void)dealloc
 {
-    sharedCocoaApplicationDelegate = nil;
     [dockMenu release];
     if (reflectionDelegate) {
         [[NSApplication sharedApplication] setDelegate:reflectionDelegate];
@@ -131,27 +135,6 @@ QT_END_NAMESPACE
     [super dealloc];
 }
 
-+ (id)allocWithZone:(NSZone *)zone
-{
-    @synchronized(self) {
-        if (sharedCocoaApplicationDelegate == nil) {
-            sharedCocoaApplicationDelegate = [super allocWithZone:zone];
-            qAddPostRoutine(cleanupCocoaApplicationDelegate);
-            return sharedCocoaApplicationDelegate;
-        }
-    }
-    return nil;
-}
-
-+ (QCocoaApplicationDelegate *)sharedDelegate
-{
-    @synchronized(self) {
-        if (sharedCocoaApplicationDelegate == nil)
-            [[self alloc] init];
-    }
-    return [[sharedCocoaApplicationDelegate retain] autorelease];
-}
-
 - (void)setDockMenu:(NSMenu*)newMenu
 {
     [newMenu retain];
@@ -284,7 +267,7 @@ QT_END_NAMESPACE
     inLaunch = false;
 
     if (qEnvironmentVariableIsEmpty("QT_MAC_DISABLE_FOREGROUND_APPLICATION_TRANSFORM")) {
-        if (QSysInfo::macVersion() >= QSysInfo::MV_10_12) {
+        if (__builtin_available(macOS 10.12, *)) {
             // Move the application window to front to avoid launching behind the terminal.
             // Ignoring other apps is necessary (we must ignore the terminal), but makes
             // Qt apps play slightly less nice with other apps when lanching from Finder