yellow.m

#include <ApplicationServices/ApplicationServices.h>
#include <Cocoa/Cocoa.h>

@interface BlortAppDelegate : NSObject <NSApplicationDelegate>
@end

@implementation BlortAppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    NSLog(@"applicationDidFinishLaunching");
    [NSApp activateIgnoringOtherApps:YES];
}
@end

static BlortAppDelegate* appDelegate = nil;
static NSWindow* ourWindow = nil;

extern void Cocoa_Init(void)
{ @autoreleasepool
    {
        [NSApplication sharedApplication];
        [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
        NSLog(@"\nFOIRST TROII!");
        [NSApp setDelegate:[[BlortAppDelegate alloc] init]];
        id menubar = [[NSMenu new] autorelease];
        id appMenuItem = [[NSMenuItem alloc]initWithTitle:@"hoo" action:nil keyEquivalent:@""];
        [menubar addItem:appMenuItem];
        
        NSSize size = NSSizeFromString(@"64x64");
        NSImage *image = [[[NSImage alloc] initWithSize:size] autorelease];
        [image lockFocus];
        [NSColor.blueColor drawSwatchInRect:NSMakeRect(0, 0, size.width, size.height)];
        [image unlockFocus];
        [NSApp setApplicationIconImage:image];
        [NSApp setMainMenu:menubar];
        
        
        NSRect frame = NSMakeRect(0, 0, 200, 200);
        NSWindow* window  = [[[NSWindow alloc] initWithContentRect:frame
                                                         styleMask:NSWindowStyleMaskBorderless
                                                           backing:NSBackingStoreBuffered
                                                             defer:NO] autorelease];
        [window setBackgroundColor:[NSColor blueColor]];
        [window makeKeyAndOrderFront:NSApp];
        ourWindow = window;
        
        [NSApp finishLaunching];
    }
}
extern void Cocoa_PumpEvents(void)
{ @autoreleasepool
    {
        NSEvent* event = [NSApp nextEventMatchingMask:NSEventMaskAny untilDate:[NSDate distantPast] inMode:NSDefaultRunLoopMode dequeue:YES ];
    }
}

Did u try stepping with the debugger to the same point in which we are getting the crash when used from SBCL?
Maybe we could figure-out what should be the resource (image) that is a null pointer in SBCL, some resource that a cocoa app initialised with setActivationPolicy:NSApplicationActivationPolicyRegular should have but SBCL does not?

I'v been using the same SDL lib on my system from different places, Kotlin Native (also FFI), C, C++ etc. these days, all works fine except SBCL.