[mono][wasm] Store the exception object in a GC handle while it is being thrown. (#67121)

src/mono/mono/mini/mini-exceptions.c

@@ -2493,7 +2493,8 @@ mono_handle_exception_internal (MonoContext *ctx, MonoObject *obj, gboolean resu
 						 * methods, then execute the clause and the rest of the method
 						 * using the interpreter.
 						 */
-						jit_tls->resume_state.ex_obj = obj;
+						g_assert (!jit_tls->resume_state.ex_gchandle);
+						jit_tls->resume_state.ex_gchandle = mono_gchandle_new_internal ((MonoObject*)obj, TRUE);
 						jit_tls->resume_state.ji = ji;
 						jit_tls->resume_state.clause_index = i;
 						jit_tls->resume_state.il_state = frame.il_state;
@@ -3579,13 +3580,17 @@ mini_llvmonly_resume_exception_il_state (MonoLMF *lmf, gpointer info)
 	}
 	jit_tls->resume_state.il_state = NULL;
 
+	MonoObject *ex_obj = mono_gchandle_get_target_internal (jit_tls->resume_state.ex_gchandle);
+	mono_gchandle_free_internal (jit_tls->resume_state.ex_gchandle);
+	jit_tls->resume_state.ex_gchandle = NULL;
+
 	/* Pop the LMF frame so the caller doesn't have to do it */
 	mono_set_lmf ((MonoLMF *)(((gsize)lmf->previous_lmf) & ~3));
 
 	MonoJitInfo *ji = jit_tls->resume_state.ji;
 	int clause_index = jit_tls->resume_state.clause_index;
 	MonoJitExceptionInfo *ei = &ji->clauses [clause_index];
-	gboolean r = mini_get_interp_callbacks ()->run_clause_with_il_state (il_state, clause_index, ei->handler_start, NULL, jit_tls->resume_state.ex_obj, NULL, MONO_EXCEPTION_CLAUSE_NONE);
+	gboolean r = mini_get_interp_callbacks ()->run_clause_with_il_state (il_state, clause_index, ei->handler_start, NULL, ex_obj, NULL, MONO_EXCEPTION_CLAUSE_NONE);
 	if (r)
 		/* Another exception thrown, continue unwinding */
 		mono_llvm_cpp_throw_exception ();

src/mono/mono/mini/mini-runtime.h

@@ -130,6 +130,7 @@ typedef struct {
 	int first_filter_idx, filter_idx;
 	/* MonoMethodILState */
 	gpointer il_state;
+	MonoGCHandle ex_gchandle;
 } ResumeState;
 
 typedef void (*MonoAbortFunction)(MonoObject*);