Question

The scenario is pretty straighforward, I’ve embedded mono runtime 2.10.8 in my app, and I’m calling the managed methods via pointers obtained by: mono_method_get_unmanaged_thunk:

// obtain pointer
bool (__stdcall*foo) (MonoException**);
foo = mono_method_get_unmanaged_thunk(somemethod);

// call it
MonoException* exc;
foo(&exc);
if(exc)
    // handle exception
// nothing else...

What puzzles me, that I’m doing nothing else with the MonoException pointer (documentation I’ve read doesn’t say anything about this). Is it removal handled by the managed runtime? If so, how it can be sure that my native side is not holding a pointer to it?

Edit

I’ve read through the sources and found out that exceptions are just pointers to objects created with mono_object_new, so they are subject of the garbage collection.

Now, I’ve also read that if I want to keep some pointer on native side and prevent it from being garbaged I need to obtain GC handle for it. So the (modified) question now is:

If the point of returned pointer to exception object is only to serve as error reporting facility, and such error reporting is made right after the managed call, is it safe to assume it won’t get garbaged before I handle it (without using gc handle)?

Answer 1

To quote the page you linked:
Note that this registration is not necessary for LOCAL variables, as they are stored on the stack. It is only necessary for global variables, as they are not a part of the GC’s root set.

So that means in your scenario you don’t have to allocate a handle.