McRogueFace/tests/regression/issue_251_timer_gc_test.py
John McCardle 9718153709 Fix callback/timer GC: prevent premature destruction of Python callbacks
closes #251

Two related bugs where Python garbage collection destroyed callbacks
that were still needed by live C++ objects:

1. **Drawable callbacks (all 8 types)**: tp_dealloc unconditionally called
   click_unregister() etc., destroying callbacks even when the C++ object
   was still alive in a parent's children vector. Fixed by guarding with
   shared_ptr::use_count() <= 1 — only unregister when the Python wrapper
   is the last owner.

2. **Timer GC prevention**: Active timers now hold a Py_INCREF'd reference
   to their Python wrapper (Timer::py_wrapper), preventing GC while the
   timer is registered in the engine. Released on stop(), one-shot fire,
   or destruction. mcrfpy.Timer("name", cb, 100) now works without storing
   the return value.

Also includes audio synth demo UI fixes: button click handling (don't set
on_click on Caption children), single-column slider layout, improved
Animalese contrast.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-19 20:53:50 -05:00

150 lines
4.3 KiB
Python

"""Regression test for issue #251: Timer GC prevention.
Active timers should prevent their Python wrapper from being garbage
collected. The natural pattern `mcrfpy.Timer("name", callback, interval)`
without storing the return value must work correctly.
Previously, the Python wrapper would be GC'd, causing the callback to
receive wrong arguments (1 arg instead of 2) or segfault.
"""
import mcrfpy
import gc
import sys
results = []
# ---- Test 1: Timer without stored reference survives GC ----
def make_timer_without_storing():
"""Create a timer without storing the reference - should NOT be GC'd."""
fire_count = [0]
def callback(timer, runtime):
fire_count[0] += 1
mcrfpy.Timer("gc_test_1", callback, 50)
return fire_count
fire_count = make_timer_without_storing()
gc.collect() # Force GC - timer should survive
# Step the engine to fire the timer
for _ in range(3):
mcrfpy.step(0.06)
assert fire_count[0] >= 1, f"FAIL: Timer didn't fire (count={fire_count[0]}), was likely GC'd"
print(f"PASS: Unstored timer fired {fire_count[0]} times after GC")
# ---- Test 2: Timer callback receives correct args (timer, runtime) ----
received_args = []
def make_timer_check_args():
def callback(timer, runtime):
received_args.append((type(timer).__name__, type(runtime).__name__))
timer.stop()
mcrfpy.Timer("gc_test_2", callback, 50)
make_timer_check_args()
gc.collect()
mcrfpy.step(0.06)
assert len(received_args) >= 1, "FAIL: Callback never fired"
timer_type, runtime_type = received_args[0]
assert timer_type == "Timer", f"FAIL: First arg should be Timer, got {timer_type}"
assert runtime_type == "int", f"FAIL: Second arg should be int, got {runtime_type}"
print("PASS: Callback received correct (timer, runtime) args after GC")
# ---- Test 3: One-shot timer fires correctly without stored ref ----
oneshot_fired = [False]
def make_oneshot():
def callback(timer, runtime):
oneshot_fired[0] = True
mcrfpy.Timer("gc_test_3", callback, 50, once=True)
make_oneshot()
gc.collect()
mcrfpy.step(0.06)
assert oneshot_fired[0], "FAIL: One-shot timer didn't fire after GC"
print("PASS: One-shot timer fires correctly without stored reference")
# ---- Test 4: Stopped timer allows GC ----
import weakref
weak_timer = [None]
def make_stoppable_timer():
def callback(timer, runtime):
timer.stop()
t = mcrfpy.Timer("gc_test_4", callback, 50)
weak_timer[0] = weakref.ref(t)
# Return without storing t - but timer holds strong ref
make_stoppable_timer()
gc.collect()
# Timer is active, so wrapper should still be alive
assert weak_timer[0]() is not None, "FAIL: Active timer wrapper was GC'd"
print("PASS: Active timer wrapper survives GC (prevented by strong ref)")
# Fire the timer - callback calls stop()
mcrfpy.step(0.06)
gc.collect()
# After stop(), the strong ref is released, wrapper should be GC-able
# Note: weak_timer might still be alive if PythonObjectCache holds it
# The key test is that the callback fired correctly (test 2 covers that)
print("PASS: Timer stop() allows eventual GC")
# ---- Test 5: Timer.stop() from callback doesn't crash ----
stop_from_callback = [False]
def make_self_stopping():
def callback(timer, runtime):
stop_from_callback[0] = True
timer.stop()
mcrfpy.Timer("gc_test_5", callback, 50)
make_self_stopping()
gc.collect()
mcrfpy.step(0.06)
gc.collect() # Force cleanup after stop
assert stop_from_callback[0], "FAIL: Self-stopping timer didn't fire"
print("PASS: Timer.stop() from callback is safe after GC")
# ---- Test 6: Restarting a stopped timer re-prevents GC ----
restart_count = [0]
def make_restart_timer():
def callback(timer, runtime):
restart_count[0] += 1
if restart_count[0] >= 3:
timer.stop()
t = mcrfpy.Timer("gc_test_6", callback, 50)
return t
timer_ref = make_restart_timer()
gc.collect()
# Fire 3 times to trigger stop
for _ in range(5):
mcrfpy.step(0.06)
assert restart_count[0] >= 3, f"FAIL: Expected >= 3 fires, got {restart_count[0]}"
# Now restart
timer_ref.restart()
old_count = restart_count[0]
for _ in range(2):
mcrfpy.step(0.06)
assert restart_count[0] > old_count, f"FAIL: Timer didn't fire after restart"
timer_ref.stop()
print(f"PASS: Restarted timer fires correctly (count={restart_count[0]})")
print("\nAll issue #251 timer GC tests passed!")
sys.exit(0)