diff --git a/src/osx_app.m b/src/osx_app.m
index ac8a5ca..d690217 100644
--- a/src/osx_app.m
+++ b/src/osx_app.m
@@ -1712,14 +1712,10 @@ void mg_osx_surface_set_frame(mg_surface_data* surface, mp_rect frame)
 {@autoreleasepool{
 	CGRect cgFrame = {{frame.x, frame.y}, {frame.w, frame.h}};
 
-//	dispatch_async(dispatch_get_main_queue(),
-//		^{
-			[CATransaction begin];
-			[CATransaction setDisableActions:YES];
-			[surface->layer.caLayer setFrame: cgFrame];
-			[CATransaction commit];
-//		});
-
+	[CATransaction begin];
+	[CATransaction setDisableActions:YES];
+	[surface->layer.caLayer setFrame: cgFrame];
+	[CATransaction commit];
 }}
 
 bool mg_osx_surface_get_hidden(mg_surface_data* surface)
@@ -2222,27 +2218,44 @@ int mp_alert_popup(const char* title,
                    uint32 count,
                    const char** options)
 {
-	@autoreleasepool
-	{
-		NSWindow *keyWindow = [NSApp keyWindow];
+	__block int result = 0;
 
-		NSAlert* alert = [[NSAlert alloc] init];
-		NSString* string;
-		for(int i=count-1;i>=0;i--)
+	dispatch_block_t block = ^{
+		@autoreleasepool
 		{
-			string = [[NSString alloc] initWithUTF8String:options[i]];
-			[alert addButtonWithTitle:string];
-			[string release];
-		}
-		string = [[NSString alloc] initWithUTF8String:message];
-		[alert setMessageText:string];
-		[string release];
+			NSWindow *keyWindow = [NSApp keyWindow];
 
-		[alert setAlertStyle:NSAlertStyleWarning];
-		int result = count - ([alert runModal]-NSAlertFirstButtonReturn) - 1;
-		[keyWindow makeKeyWindow];
-		return(result);
+			NSAlert* alert = [[NSAlert alloc] init];
+			NSString* string;
+			for(int i=count-1;i>=0;i--)
+			{
+				string = [[NSString alloc] initWithUTF8String:options[i]];
+				[alert addButtonWithTitle:string];
+				[string release];
+			}
+			string = [[NSString alloc] initWithUTF8String:title];
+			[alert setMessageText:string];
+			[string release];
+
+			string = [[NSString alloc] initWithUTF8String:message];
+			[alert setInformativeText:string];
+			[string release];
+
+			[alert setAlertStyle:NSAlertStyleWarning];
+			result = count - ([alert runModal]-NSAlertFirstButtonReturn) - 1;
+			[keyWindow makeKeyWindow];
+		}
+	};
+
+	if([NSThread isMainThread])
+	{
+		block();
 	}
+	else
+	{
+		dispatch_sync(dispatch_get_main_queue(), block);
+	}
+	return(result);
 }
 
 
diff --git a/src/platform/platform_varg.h b/src/platform/platform_varg.h
new file mode 100644
index 0000000..5c2c713
--- /dev/null
+++ b/src/platform/platform_varg.h
@@ -0,0 +1,22 @@
+/************************************************************//**
+*
+*	@file: platform_varg.h
+*	@author: Martin Fouilleul
+*	@date: 17/04/2023
+*
+*****************************************************************/
+#ifndef __PLATFORM_VARG_H_
+#define __PLATFORM_VARG_H_
+
+#include"platform.h"
+
+#if PLATFORM_ORCA
+	#define va_start __builtin_va_start
+	#define va_arg __builtin_va_arg
+	#define va_copy __builtin_va_copy
+	#define va_end __builtin_va_end
+#else
+	#include<stdarg.h>
+#endif
+
+#endif //__PLATFORM_VARG_H_
diff --git a/src/util/debug_log.c b/src/util/debug_log.c
index c750b55..6dacb59 100644
--- a/src/util/debug_log.c
+++ b/src/util/debug_log.c
@@ -6,10 +6,11 @@
 *	@revision:
 *
 *****************************************************************/
-#include<stdarg.h>
 #include<string.h>
 #include"debug_log.h"
 
+#include"platform_varg.h"
+
 static const char* LOG_HEADINGS[LOG_LEVEL_COUNT] = {
 	"Error",
 	"Warning",
diff --git a/src/util/macro_helpers.h b/src/util/macro_helpers.h
index dc3b93c..0c48f1a 100644
--- a/src/util/macro_helpers.h
+++ b/src/util/macro_helpers.h
@@ -124,10 +124,10 @@ static inline u64 next_pow2_u64(u64 x)
 
 #ifndef NO_ASSERT
 	#ifdef PLATFORM_ORCA
-		//TODO add a runtime-provided assert
-		extern void orca_assert(bool x);
+		extern int orca_assert(const char* file, const char* function, int line, const char* src, const char* msg);
 
-		#define _ASSERT_(x, msg) orca_assert(x)
+		#define ORCA_ASSERT(x, msg) ((x) || orca_assert(__FILE__, __FUNCTION__, __LINE__, #x, msg))
+		#define _ASSERT_(x, msg) ORCA_ASSERT(x, msg)
 	#else
 		#include<assert.h>
 		#define _ASSERT_(x, msg) assert(x && msg)