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Fix object leaks caused by unfulfilled yields

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Now the stack saved in a `GDScriptFunctionState` is cleared as soon as the `yield()` operation is known not to be resumed because either the script, the instance or both are deleted.

This clears problems like leaked objects by eliminating cases of circular references between `GDScriptFunctionState`s preventing them and the objects they refer to in their saved stacks from being released. As an example, this makes using `SceneTreeTimer` safer.

Furthermore, with this change it's now possible to print early warnings about `yield()`s to released script/instances, as now we know they won't be successfully resumed as the condition for that happens. However, this PR doesn't add such messages, to keep the observed behavior the same for the time being.

Also, now a backup of the function name in `GDScriptFunctionState` is used, since the script may not be valid by the time the function name is needed for the resume-after-yield error messages.
This commit is contained in:
Pedro J. Estébanez 2020-05-05 12:53:05 +02:00
parent 1c23a0cc7f
commit 46bfe4452f
5 changed files with 91 additions and 32 deletions
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83
modules/gdscript/gdscript_function.cpp
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@ -294,8 +294,8 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
line = p_state->line;
ip = p_state->ip;
alloca_size = p_state->stack.size();
script = static_cast<GDScript *>(ObjectDB::get_instance(p_state->script_id));
p_instance = p_state->instance_id.is_valid() ? static_cast<GDScriptInstance *>(ObjectDB::get_instance(p_state->instance_id)->get_script_instance()) : nullptr;
script = p_state->script;
p_instance = p_state->instance;
defarg = p_state->defarg;
self = p_state->self;
@ -1281,11 +1281,21 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
gdfs->state.alloca_size = alloca_size;
gdfs->state.ip = ip + ipofs;
gdfs->state.line = line;
gdfs->state.script_id = script->get_instance_id();
gdfs->state.script = _script;
{
MutexLock lock(GDScriptLanguage::get_singleton()->lock);
_script->pending_func_states.add(&gdfs->scripts_list);
if (p_instance) {
gdfs->state.instance = p_instance;
p_instance->pending_func_states.add(&gdfs->instances_list);
} else {
gdfs->state.instance = NULL;
}
}
#ifdef DEBUG_ENABLED
gdfs->state.function_name = name;
gdfs->state.script_path = _script->get_path();
#endif
gdfs->state.instance_id = (p_instance && p_instance->get_owner()) ? p_instance->get_owner()->get_instance_id() : ObjectID();
gdfs->state.defarg = defarg;
gdfs->function = this;
@ -1833,12 +1843,14 @@ bool GDScriptFunctionState::is_valid(bool p_extended_check) const {
return false;
if (p_extended_check) {
// Class instance gone? (Otherwise script is valid for sure, because the instance has a ref to the script)
if (state.instance_id.is_valid() && !ObjectDB::get_instance(state.instance_id)) {
MutexLock lock(GDScriptLanguage::get_singleton()->lock);
// Script gone?
if (!scripts_list.in_list()) {
return false;
}
// Script gone? (Static method, so there's no instance whose ref to the script can ensure it's valid)
if (!ObjectDB::get_instance(state.script_id)) {
// Class instance gone? (if not static function)
if (state.instance && !instances_list.in_list()) {
return false;
}
}
@ -1849,19 +1861,26 @@ bool GDScriptFunctionState::is_valid(bool p_extended_check) const {
Variant GDScriptFunctionState::resume(const Variant &p_arg) {
ERR_FAIL_COND_V(!function, Variant());
if (state.instance_id.is_valid() && !ObjectDB::get_instance(state.instance_id)) {
{
MutexLock lock(GDScriptLanguage::singleton->lock);
if (!scripts_list.in_list()) {
#ifdef DEBUG_ENABLED
ERR_FAIL_V_MSG(Variant(), "Resumed function '" + String(function->get_name()) + "()' after yield, but class instance is gone. At script: " + state.script_path + ":" + itos(state.line));
ERR_FAIL_V_MSG(Variant(), "Resumed function '" + state.function_name + "()' after yield, but script is gone. At script: " + state.script_path + ":" + itos(state.line));
#else
return Variant();
return Variant();
#endif
}
if (!ObjectDB::get_instance(state.script_id)) {
}
if (state.instance && !instances_list.in_list()) {
#ifdef DEBUG_ENABLED
ERR_FAIL_V_MSG(Variant(), "Resumed function '" + String(function->get_name()) + "()' after yield, but script is gone. At script: " + state.script_path + ":" + itos(state.line));
ERR_FAIL_V_MSG(Variant(), "Resumed function '" + state.function_name + "()' after yield, but class instance is gone. At script: " + state.script_path + ":" + itos(state.line));
#else
return Variant();
return Variant();
#endif
}
// Do these now to avoid locking again after the call
scripts_list.remove_from_list();
instances_list.remove_from_list();
}
state.result = p_arg;
@ -1884,6 +1903,8 @@ Variant GDScriptFunctionState::resume(const Variant &p_arg) {
state.result = Variant();
if (completed) {
_clear_stack();
if (first_state.is_valid()) {
first_state->emit_signal("completed", ret);
} else {
@ -1893,18 +1914,22 @@ Variant GDScriptFunctionState::resume(const Variant &p_arg) {
#ifdef DEBUG_ENABLED
if (EngineDebugger::is_active())
GDScriptLanguage::get_singleton()->exit_function();
if (state.stack_size) {
//free stack
Variant *stack = (Variant *)state.stack.ptr();
for (int i = 0; i < state.stack_size; i++)
stack[i].~Variant();
}
#endif
}
return ret;
}
void GDScriptFunctionState::_clear_stack() {
if (state.stack_size) {
Variant *stack = (Variant *)state.stack.ptr();
for (int i = 0; i < state.stack_size; i++)
stack[i].~Variant();
state.stack_size = 0;
}
}
void GDScriptFunctionState::_bind_methods() {
ClassDB::bind_method(D_METHOD("resume", "arg"), &GDScriptFunctionState::resume, DEFVAL(Variant()));
@ -1914,18 +1939,20 @@ void GDScriptFunctionState::_bind_methods() {
ADD_SIGNAL(MethodInfo("completed", PropertyInfo(Variant::NIL, "result", PROPERTY_HINT_NONE, "", PROPERTY_USAGE_NIL_IS_VARIANT)));
}
GDScriptFunctionState::GDScriptFunctionState() {
GDScriptFunctionState::GDScriptFunctionState() :
scripts_list(this),
instances_list(this) {
function = nullptr;
}
GDScriptFunctionState::~GDScriptFunctionState() {
if (function != nullptr) {
//never called, deinitialize stack
for (int i = 0; i < state.stack_size; i++) {
Variant *v = (Variant *)&state.stack[sizeof(Variant) * i];
v->~Variant();
}
_clear_stack();
{
MutexLock lock(GDScriptLanguage::singleton->lock);
scripts_list.remove_from_list();
instances_list.remove_from_list();
}
}