test_capi fails if run with --forever argument

[Eclips4]

Tried on current main:
Fails on test_capi/test_misc/TestOptimizerAPI.test_counter_optimizer

./python -m test -v test_capi -m test_misc -m TestOptimizerAPI --forever
... many lines
======================================================================
FAIL: test_counter_optimizer (test.test_capi.test_misc.TestOptimizerAPI.test_counter_optimizer)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\Users\KIRILL-1\CLionProjects\cpython\Lib\test\test_capi\test_misc.py", line 1929, in test_counter_optimizer
    self.assertEqual(opt.get_count(), 1000)
AssertionError: 0 != 1000

----------------------------------------------------------------------
Ran 168 tests in 6.590s

FAILED (failures=1, skipped=5)
test test_capi failed
test_capi failed (1 failure)

== Tests result: FAILURE ==

1 test OK.

1 test failed:
    test_capi

Total duration: 13.2 sec
Tests result: FAILURE

[Eclips4]

Seems to be introduced in #105100
cc @markshannon

[AlexWaygood]

Fixed by #105683

[sunmy2019]

I am testing heads/main: 6a80664 and the issue happens again.

./python -m test -R 3:3 -v test_capi -m test_long_loop -m test_counter_optimizer

0:00:00 load avg: 0.62 Run tests sequentially
0:00:00 load avg: 0.62 [1/1] test_capi
beginning 6 repetitions
123456
test_counter_optimizer (test.test_capi.test_misc.TestOptimizerAPI.test_counter_optimizer) ... ok
test_long_loop (test.test_capi.test_misc.TestOptimizerAPI.test_long_loop)
Check that we aren't confused by EXTENDED_ARG ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.001s

OK
.test_counter_optimizer (test.test_capi.test_misc.TestOptimizerAPI.test_counter_optimizer) ... FAIL
test_long_loop (test.test_capi.test_misc.TestOptimizerAPI.test_long_loop)
Check that we aren't confused by EXTENDED_ARG ... FAIL

======================================================================
FAIL: test_counter_optimizer (test.test_capi.test_misc.TestOptimizerAPI.test_counter_optimizer)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/xxx/cpython/Lib/test/test_capi/test_misc.py", line 2386, in test_counter_optimizer
    self.assertEqual(opt.get_count(), 1000)
AssertionError: 0 != 1000

======================================================================
FAIL: test_long_loop (test.test_capi.test_misc.TestOptimizerAPI.test_long_loop)
Check that we aren't confused by EXTENDED_ARG
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/xxx/cpython/Lib/test/test_capi/test_misc.py", line 2408, in test_long_loop
    self.assertEqual(opt.get_count(), 10)
AssertionError: 0 != 10

----------------------------------------------------------------------
Ran 2 tests in 0.002s

FAILED (failures=2)
test test_capi failed
test_capi failed (2 failures)

== Tests result: FAILURE ==

1 test failed:
    test_capi

Total duration: 76 ms
Tests result: FAILURE

[markshannon]

Fixed by #105683

Unfortunately not.

[gvanrossum]

Just got hit by this (it makes the refleak buildbots fail in #105924).

I've got a hunch the problem is in deopt_code() (in codeobject.c), but I can't quite nail it. I put a printf() there when opcode == ENTER_EXECUTOR, and in the loop in the test which executes five times, it prints only four times?! Then the second time the whole test is re-run, it prints never at all (but the test fails after the first time through the loop). It appears the first iteration (out of five in the test -- for repeat in range(5)) doesn't cause any executor to be cleared when clear_executors() sets func.__code__ = func.__code__.replace(). But the first iteration clearly has an executor, because the assert passes (the first time the whole test is run).

Not sure where this really points, but the logic in deopt_code() is subtle (it gets the opcode from _Py_GetBaseOpcode(code, i), then patches instructions[i]). I get lost when I try to understand _Py_GetBaseOpcode().

[gvanrossum]

This was now fixed by @vstinner in #106171. His fix is to create a whole new function object (by using exec). This is needed because the original code object is kept alive by the parent code object -- and the only way to clear a code object's co_executors array is to cause the code object to be finalized.

(I tried putting the assignment to func.__code__ in front of the yield, but it didn't seem to work.)

Arguably we ought to have an explicit API for this, but that can wait.