Expanding NSColor in debugger crashes app

[chamons]

Steps to Reproduce

1. New XM App
2. NSColor color = NSColor.Red; and set breakpoint on line after
3. Expand color in debugger
4. Boom - https://gist.github.com/chamons/be71ccd1b887a7e246bd3b42910bef7b

Expected Behavior

We don't expand unsafe properties by default in IDE.

Actual Behavior

Environment

macios master

[spouliot]

weird, the binding is annotated correctly

[Export ("blackComponent")]
nfloat BlackComponent { [MarshalNativeExceptions] get; }

and the right xamarin_* function was called

	2   CoreFoundation                      0x00007fff3bd0dc77 +[NSException raise:format:] + 193
	3   AppKit                              0x00007fff39822481 -[NSColorSpaceColor blackComponent] + 44
	4   NSColorCrash                        0x000000010206516d xamarin_nfloat_objc_msgSend + 29

but it did crash... maybe mono intercepted it before the native catch handler we generate ?

[rolfbjarne]

We caught the NSException, and then decided to rethrow it:

0x7fff66e5a507 - /usr/lib/libobjc.A.dylib : objc_exception_throw
0x1020931f1 - [...]/NSColorCrash.app/Contents/MacOS/NSColorCrash : xamarin_process_nsexception_using_mode

which means we hit this case:

xamarin-macios/runtime/runtime.m

Lines 2355 to 2359 in 99e727c

	case MarshalObjectiveCExceptionModeUnwindManagedCode:
	if (xamarin_is_gc_coop)
	xamarin_assertion_message ("Cannot unwind managed frames for Objective-C exceptions when the GC is in cooperative mode.");
	@throw ns_exception;
	break;

and that crashes because there are no other Objective-C catch handlers further up the stack.

I suspect that passing --marshal-objectivec-exceptions=throwmanagedexception to mmp will fix the problem. Admittedly this should probably be the default when debugging.

[chamons]

Nice idea Rolf - that fixed it and is a sensible default.

[chamons]

This was fixed back in #7667 and never closed.