main.m

// # To test (macOS only)
// - Copy the contents of this file into a file called main.m
// - Run `clang main.m -fobjc-arc -xobjective-c++ -framework Cocoa && ./a.out`
//   in bash
// - Send me:
//   + The copy pasted console output from the run
//   + Your macOS version (Apple > About This Mac)
//   + Your clang version (`clang --version`)
//   + Whether or not your computer has a Touch Bar
//
// # For The Curious
// I'm expecting the window I allocate to be subsequently be freed before exit,
// but on some computers, it is not. I suspect this is a bug in macOS as it
// seems like the extra retains are coming from AppKit & CoreFoundation, in
// something to do with the Touch Bar, but I'm not 100% positive. It's also
// possible I'm misunderstanding something fundamental about Objective-C memory
// management.

#import <Cocoa/Cocoa.h>

@interface Delegate: NSObject<NSWindowDelegate>
@end

@interface MyWindow: NSWindow
@end

int main() {
    @autoreleasepool {
        // Initialize the shared application
        NSApplication* app = NSApplication.sharedApplication;

        // Allow UI
        app.activationPolicy = NSApplicationActivationPolicyRegular;

        // Create the window and delegate
        NSWindow *window = [[MyWindow alloc] init];
        Delegate *delegate = [[Delegate alloc] init];
        window.delegate = delegate;

        // Have the window maintain normal refcount semantics
        window.releasedWhenClosed = NO;

        // Finish launching the app
        [app finishLaunching];
        [NSRunningApplication.currentApplication
            activateWithOptions:NSApplicationActivateAllWindows];

        // Show the window
        [window orderFront:nil];

        // Simulate the user clicking the x (canceled by the delegate). If we
        // comment out this line, or don't cancel the close in the delegate, we
        // don't get the leak.
        [window performClose:nil];

        // Actually close the window
        [window close];
    }

    NSLog(@"exit process");
}

@implementation Delegate
    - (instancetype)init {
        NSLog(@"[delegate init]");
        return [super init];
    }

    - (BOOL)windowShouldClose:(NSWindow *)sender {
        NSLog(@"[delegate windowShouldClose:] (returning NO to cancel)");
        return NO;
    }

    - (void)windowWillClose:(NSNotification *)notification {
        NSLog(@"[delegate windowWillClose:]");
    }

    - (void)dealloc {
        NSLog(@"[delegate dealloc]");
    }
@end

@implementation MyWindow
    - (instancetype)init {
        NSLog(@"[MyWindow init]");
        return [super
            initWithContentRect:NSScreen.mainScreen.visibleFrame
            styleMask:NSWindowStyleMaskTitled |
                      NSWindowStyleMaskClosable |
                      NSWindowStyleMaskMiniaturizable |
                      NSWindowStyleMaskResizable
            backing:NSBackingStoreBuffered
            defer:NO
        ];
    }

    - (void)dealloc {
        NSLog(@"[MyWindow dealloc]");
    }
@end