Python 3.15.0: test_sys.test_getallocatedblocks() fails if run after test_collections.test_odd_sizes()

[Fearless-Badger]

Bug report

Bug description:

test_sys fails while running the test suite of python 3.15.0 when --with-pydebug and --enable-optimizations are both enabled.

I get consistent failure of the test suite, but when I run the test individually, it passes. I do not know if this is expected or not, as I understand that enabling the debugger and optimizations is kind of contradictory. I included the test header, as well as the tests summary for additional info.

== CPython 3.15.0a0 (heads/main-dirty:9983c7d4416, May 19 2025, 09:41:00) [GCC 13.3.0]
== Linux-6.11.0-25-generic-x86_64-with-glibc2.39 little-endian
== Python build: debug PGO
== cwd: /home/badger/oss/cpython/build/test_python_worker_177894æ
== CPU count: 8
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 3038718328


...


0:32:13 load avg: 1.39 [396/491] test_sys
test test_sys failed -- Traceback (most recent call last):
  File "/home/badger/oss/cpython/Lib/test/test_sys.py", line 1156, in test_getallocatedblocks
    self.assertLess(a, sys.gettotalrefcount())
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 698068 not less than 663517

0:32:18 load avg: 1.36 [396/491/1] test_sys failed (1 failure)


...


== Tests result: FAILURE ==

22 tests skipped:
    test.test_asyncio.test_windows_events
    test.test_asyncio.test_windows_utils test.test_gdb.test_backtrace
    test.test_gdb.test_cfunction test.test_gdb.test_cfunction_full
    test.test_gdb.test_misc test.test_gdb.test_pretty_print
    test_android test_apple test_dbm_gnu test_dbm_ndbm test_devpoll
    test_free_threading test_kqueue test_launcher test_msvcrt
    test_startfile test_winapi test_winconsoleio test_winreg test_wmi
    test_zstd

11 tests skipped (resource denied):
    test_curses test_peg_generator test_pyrepl test_smtpnet
    test_socketserver test_tkinter test_ttk test_urllib2net
    test_urllibnet test_winsound test_zipfile64

1 test failed:
    test_sys

457 tests OK.

Total duration: 39 min 17 sec
Total tests: run=46,135 failures=1 skipped=2,164
Total test files: run=480/491 failed=1 skipped=22 resource_denied=11
Result: FAILURE

I don't suspect my local environment to be the problem, since the test suite passes when I remove the "--enable-optimizations" flag, and just enable the debugger. The variable "a" seems to change each time I run the suite, so I included the random seed.

Build setup:

Tested on Python 3.15.0.

Distributor ID:	Ubuntu
Description:	Ubuntu 24.04.2 LTS
Release:	24.04
Codename:	noble

CPU: product: Intel(R) Core(TM) i7-8665U CPU @ 1.90GHz

Configuration I used

./configure --with-pydebug --enable-optimizations 

CPython versions tested on:

3.15, CPython main branch

Operating systems tested on:

Linux

[Fearless-Badger]

After investigating further, I have found that when running the tests with ./python -m test -j3 the test suite will pass. It is only when I run the test suite with ./python -m test that "test_sys" will fail.

Basically, "test_sys.test_getallocatedblocks() " only fails when run sequentially, and as part of the full suite.

[tpburns]

I had experienced the same error with a slightly different configuration, and have been experimenting to reproduce and maybe isolate. I have now observed the bug with a configure using only the --with-pydebug flag, though similarly only in the full test suite. See below (I cleaned up the outputs a bit)

tpburns@tpb-M-linux:~/dev/cpython$ make clean -s
tpburns@tpb-M-linux:~/dev/cpython$ ./configure -q --with-pydebug
tpburns@tpb-M-linux:~/dev/cpython$ make -s
Checked 114 modules (35 built-in, 78 shared, 1 n/a on linux-x86_64, 0 disabled, 0 missing, 0 failed on import)
tpburns@tpb-M-linux:~/dev/cpython$ ./python -m unittest -v test.test_sys.SysModuleTest.test_getallocatedblocks -q
----------------------------------------------------------------------
Ran 1 test in 0.009s

OK

and

tpburns@tpb-M-linux:~/dev/cpython$ make clean -s
tpburns@tpb-M-linux:~/dev/cpython$ ./configure -q --with-pydebug
tpburns@tpb-M-linux:~/dev/cpython$ make -s
Checked 114 modules (35 built-in, 78 shared, 1 n/a on linux-x86_64, 0 disabled, 0 missing, 0 failed on import)
tpburns@tpb-M-linux:~/dev/cpython$ ./python -m test -q
Using random seed: 4087959006
0:00:00 load avg: 0.81 Run 491 tests sequentially in a single process

test test_sys failed -- Traceback (most recent call last):
  File "/home/tpburns/dev/cpython/Lib/test/test_sys.py", line 1156, in test_getallocatedblocks
    self.assertLess(a, sys.gettotalrefcount())
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 702836 not less than 669601

== Tests result: FAILURE ==

1 test failed:
    test_sys

Total duration: 28 min 21 sec
Total tests: run=46,559 failures=1 skipped=2,055
Total test files: run=480/491 failed=1 skipped=14 resource_denied=11
Result: FAILURE

This was on Ubuntu 24.04.2 LTS, Core™ i7-1195G7 × 8 processor, Python 3.15.0a0 (main),

[vstinner]

I can reproduce the issue with:

./configure --with-pydebug
make
./python -m test

[vstinner]

The test_sys.test_getallocatedblocks() failure is related to test_collections.test_odd_sizes():

$ ./python -m test test_collections test_sys -m test_odd_sizes -m test_getallocatedblocks -v
== CPython 3.15.0a0 (heads/main:27bd08273ce, May 19 2025, 22:38:56) [GCC 15.1.1 20250425 (Red Hat 15.1.1-1)]
== Linux-6.14.4-300.fc42.x86_64-x86_64-with-glibc2.41 little-endian
== Python build: debug
== cwd: /home/vstinner/python/main/build/test_python_worker_177002æ
== CPU count: 10 (process) / 12 (system)
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 3050664783
0:00:00 load avg: 0.61 Run 2 tests sequentially in a single process
0:00:00 load avg: 0.61 [1/2] test_collections
test_odd_sizes (test.test_collections.TestNamedTuple.test_odd_sizes) ... ok

----------------------------------------------------------------------
Ran 1 test in 9.453s

OK
0:00:09 load avg: 0.75 [1/2] test_collections passed
0:00:09 load avg: 0.75 [2/2] test_sys
test_getallocatedblocks (test.test_sys.SysModuleTest.test_getallocatedblocks) ... FAIL

======================================================================
FAIL: test_getallocatedblocks (test.test_sys.SysModuleTest.test_getallocatedblocks)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/vstinner/python/main/Lib/test/test_sys.py", line 1156, in test_getallocatedblocks
    self.assertLess(a, sys.gettotalrefcount())
    ~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 259399 not less than 130596

----------------------------------------------------------------------
Ran 1 test in 0.048s

FAILED (failures=1)
test test_sys failed
0:00:10 load avg: 0.75 [2/2/1] test_sys failed (1 failure)

== Tests result: FAILURE ==

1 test failed:
    test_sys

1 test OK.

Total duration: 10.3 sec
Total tests: run=2 (filtered) failures=1
Total test files: run=2/2 (filtered) failed=1
Result: FAILURE

[vstinner]

According to git bisect, it started to fail at commit 2498c22.

commit 2498c22fa0a2b560491bc503fa676585c1a603d0
Author: Mark Shannon <mark@hotpy.org>
Date:   Wed Feb 19 11:44:57 2025 +0000

    GH-91079: Implement C stack limits using addresses, not counters. (GH-130007)

[vstinner]

The following change introduced the regression:

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index f31d98bf731..6a2b316e3f6 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -2634,7 +2634,7 @@ def get_c_recursion_limit():
 
 def exceeds_recursion_limit():
     """For recursion tests, easily exceeds default recursion limit."""
-    return get_c_recursion_limit() * 3
+    return 100_000
 
 
 # Windows doesn't have os.uname() but it doesn't support s390x.