From 328aadc0ef77f51c06d657acaeba205d56e54d13 Mon Sep 17 00:00:00 2001
From: George Marques <george@gmarqu.es>
Date: Fri, 27 May 2022 09:13:25 -0300
Subject: [PATCH] GDScript: Fix stack overflow when using multiple `await`

---
 modules/gdscript/gdscript_function.cpp |  2 ++
 modules/gdscript/gdscript_vm.cpp       | 23 +++++++++++++----------
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/modules/gdscript/gdscript_function.cpp b/modules/gdscript/gdscript_function.cpp
index deef593f3410..cd3b7d69c57e 100644
--- a/modules/gdscript/gdscript_function.cpp
+++ b/modules/gdscript/gdscript_function.cpp
@@ -270,6 +270,8 @@ Variant GDScriptFunctionState::resume(const Variant &p_arg) {
 		if (EngineDebugger::is_active()) {
 			GDScriptLanguage::get_singleton()->exit_function();
 		}
+
+		_clear_stack();
 #endif
 	}
 
diff --git a/modules/gdscript/gdscript_vm.cpp b/modules/gdscript/gdscript_vm.cpp
index 8f85d8159b6a..55f4ebb1c5eb 100644
--- a/modules/gdscript/gdscript_vm.cpp
+++ b/modules/gdscript/gdscript_vm.cpp
@@ -3450,23 +3450,26 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 		GDScriptLanguage::get_singleton()->script_frame_time += time_taken - function_call_time;
 	}
 
-	// Check if this function has been interrupted by `await`.
-	// If that is the case we want to keep it in the debugger until it actually exits.
+	// Check if this is not the last time it was interrupted by `await` or if it's the first time executing.
+	// If that is the case then we exit the function as normal. Otherwise we postpone it until the last `await` is completed.
 	// This ensures the call stack can be properly shown when using `await`, showing what resumed the function.
-	if (!awaited) {
+	if (!p_state || awaited) {
 		if (EngineDebugger::is_active()) {
 			GDScriptLanguage::get_singleton()->exit_function();
 		}
+#endif
+
+		// Free stack, except reserved addresses.
+		for (int i = 3; i < _stack_size; i++) {
+			stack[i].~Variant();
+		}
+#ifdef DEBUG_ENABLED
 	}
 #endif
 
-	// Clear the stack even if there was an `await`.
-	// The stack saved in the state is a copy, so this needs to be destructed to avoid leaks.
-	if (_stack_size) {
-		// Free stack.
-		for (int i = 0; i < _stack_size; i++) {
-			stack[i].~Variant();
-		}
+	// Always free reserved addresses, since they are never copied.
+	for (int i = 0; i < 3; i++) {
+		stack[i].~Variant();
 	}
 
 	return retvalue;