posix_spawn and posix_spawnp tests failing on NetBSD with stack limit assertions

[furkanonder]

Bug report

Bug description:

Multiple tests in test_posix for posix_spawn and posix_spawnp functionality are failing on NetBSD with stack limit-related assertions in the spawned processes. All failing tests show child processes exiting with code -6 (SIGABRT).

Environment

CPython version: 3.14.0a6+ (heads/main:557d2d20d48, Mar 23 2025)
Platform: NetBSD-10.0-amd64-x86_64-64bit-ELF little-endian
Build Flags: --with-debug

Tests

./python -m test test_posix -m TestPosixSpawn -m TestPosixSpawnP -v

Output:

─./python -m test test_posix -m TestPosixSpawn -m TestPosixSpawnP -v 
== CPython 3.14.0a6+ (heads/main:557d2d20d48, Mar 23 2025, 15:29:59) [GCC 10.5.0]
== NetBSD-10.0-amd64-x86_64-64bit-ELF little-endian
== Python build: debug
== cwd: /home/blue/cpython/build/test_python_worker_362æ
== CPU count: 16
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 1713724710
0:00:00 load avg: 0.17 Run 1 test sequentially in a single process
0:00:00 load avg: 0.17 [1/1] test_posix
test_bad_file_actions (test.test_posix.TestPosixSpawn.test_bad_file_actions) ... ok
test_close_file (test.test_posix.TestPosixSpawn.test_close_file) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_dup2 (test.test_posix.TestPosixSpawn.test_dup2) ... ok
test_empty_file_actions (test.test_posix.TestPosixSpawn.test_empty_file_actions) ... ok
test_multiple_file_actions (test.test_posix.TestPosixSpawn.test_multiple_file_actions) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_no_such_executable (test.test_posix.TestPosixSpawn.test_no_such_executable) ... ok
test_none_file_actions (test.test_posix.TestPosixSpawn.test_none_file_actions) ... ok
test_open_file (test.test_posix.TestPosixSpawn.test_open_file) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_resetids (test.test_posix.TestPosixSpawn.test_resetids) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_resetids_explicit_default (test.test_posix.TestPosixSpawn.test_resetids_explicit_default) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_returns_pid (test.test_posix.TestPosixSpawn.test_returns_pid) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup (test.test_posix.TestPosixSpawn.test_setpgroup) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup_wrong_type (test.test_posix.TestPosixSpawn.test_setpgroup_wrong_type) ... ok
test_setscheduler_only_param (test.test_posix.TestPosixSpawn.test_setscheduler_only_param) ... skipped 'bpo-34685: test can fail on BSD'
test_setscheduler_with_policy (test.test_posix.TestPosixSpawn.test_setscheduler_with_policy) ... skipped 'bpo-34685: test can fail on BSD'
test_setsid (test.test_posix.TestPosixSpawn.test_setsid) ... skipped "setsid is not supported: NotImplementedError('posix_spawn: setsid unavailable on this platform')"
test_setsigdef (test.test_posix.TestPosixSpawn.test_setsigdef) ... ok
test_setsigdef_wrong_type (test.test_posix.TestPosixSpawn.test_setsigdef_wrong_type) ... ok
test_setsigmask (test.test_posix.TestPosixSpawn.test_setsigmask) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setsigmask_wrong_type (test.test_posix.TestPosixSpawn.test_setsigmask_wrong_type) ... ok
test_specify_environment (test.test_posix.TestPosixSpawn.test_specify_environment) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_bad_file_actions (test.test_posix.TestPosixSpawnP.test_bad_file_actions) ... ok
test_close_file (test.test_posix.TestPosixSpawnP.test_close_file) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_dup2 (test.test_posix.TestPosixSpawnP.test_dup2) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_empty_file_actions (test.test_posix.TestPosixSpawnP.test_empty_file_actions) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_multiple_file_actions (test.test_posix.TestPosixSpawnP.test_multiple_file_actions) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_no_such_executable (test.test_posix.TestPosixSpawnP.test_no_such_executable) ... ok
test_none_file_actions (test.test_posix.TestPosixSpawnP.test_none_file_actions) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_open_file (test.test_posix.TestPosixSpawnP.test_open_file) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_posix_spawnp (test.test_posix.TestPosixSpawnP.test_posix_spawnp) ... ok
test_resetids (test.test_posix.TestPosixSpawnP.test_resetids) ... assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 467, function "_Py_InitializeRecursionLimits"
FAIL
test_resetids_explicit_default (test.test_posix.TestPosixSpawnP.test_resetids_explicit_default) ... assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 467, function "_Py_InitializeRecursionLimits"
FAIL
test_returns_pid (test.test_posix.TestPosixSpawnP.test_returns_pid) ... assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 467, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup (test.test_posix.TestPosixSpawnP.test_setpgroup) ... assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 467, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup_wrong_type (test.test_posix.TestPosixSpawnP.test_setpgroup_wrong_type) ... ok
test_setscheduler_only_param (test.test_posix.TestPosixSpawnP.test_setscheduler_only_param) ... skipped 'bpo-34685: test can fail on BSD'
test_setscheduler_with_policy (test.test_posix.TestPosixSpawnP.test_setscheduler_with_policy) ... skipped 'bpo-34685: test can fail on BSD'
test_setsid (test.test_posix.TestPosixSpawnP.test_setsid) ... skipped "setsid is not supported: NotImplementedError('posix_spawnp: setsid unavailable on this platform')"
test_setsigdef (test.test_posix.TestPosixSpawnP.test_setsigdef) ... assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 467, function "_Py_InitializeRecursionLimits"
FAIL
test_setsigdef_wrong_type (test.test_posix.TestPosixSpawnP.test_setsigdef_wrong_type) ... ok
test_setsigmask (test.test_posix.TestPosixSpawnP.test_setsigmask) ... ok
test_setsigmask_wrong_type (test.test_posix.TestPosixSpawnP.test_setsigmask_wrong_type) ... ok
test_specify_environment (test.test_posix.TestPosixSpawnP.test_specify_environment) ... assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL

======================================================================
FAIL: test_close_file (test.test_posix.TestPosixSpawn.test_close_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2087, in test_close_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 14888 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_multiple_file_actions (test.test_posix.TestPosixSpawn.test_multiple_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2021, in test_multiple_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 4875 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_open_file (test.test_posix.TestPosixSpawn.test_open_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2068, in test_open_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 22411 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids (test.test_posix.TestPosixSpawn.test_resetids)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1860, in test_resetids
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 6982 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids_explicit_default (test.test_posix.TestPosixSpawn.test_resetids_explicit_default)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1851, in test_resetids_explicit_default
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 9121 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_returns_pid (test.test_posix.TestPosixSpawn.test_returns_pid)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1792, in test_returns_pid
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 20376 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setpgroup (test.test_posix.TestPosixSpawn.test_setpgroup)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1869, in test_setpgroup
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 29677 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setsigmask (test.test_posix.TestPosixSpawn.test_setsigmask)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1890, in test_setsigmask
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 29091 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_specify_environment (test.test_posix.TestPosixSpawn.test_specify_environment)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1822, in test_specify_environment
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 26401 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_close_file (test.test_posix.TestPosixSpawnP.test_close_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2087, in test_close_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 2519 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_dup2 (test.test_posix.TestPosixSpawnP.test_dup2)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2105, in test_dup2
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 10663 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_empty_file_actions (test.test_posix.TestPosixSpawnP.test_empty_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1842, in test_empty_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 29538 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_multiple_file_actions (test.test_posix.TestPosixSpawnP.test_multiple_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2021, in test_multiple_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 13306 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_none_file_actions (test.test_posix.TestPosixSpawnP.test_none_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1833, in test_none_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 4660 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_open_file (test.test_posix.TestPosixSpawnP.test_open_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2068, in test_open_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 15283 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids (test.test_posix.TestPosixSpawnP.test_resetids)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1860, in test_resetids
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 27835 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids_explicit_default (test.test_posix.TestPosixSpawnP.test_resetids_explicit_default)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1851, in test_resetids_explicit_default
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 12737 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_returns_pid (test.test_posix.TestPosixSpawnP.test_returns_pid)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1792, in test_returns_pid
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 1830 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setpgroup (test.test_posix.TestPosixSpawnP.test_setpgroup)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1869, in test_setpgroup
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 24458 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setsigdef (test.test_posix.TestPosixSpawnP.test_setsigdef)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1955, in test_setsigdef
 support.wait_process(pid, exitcode=-signal.SIGUSR1)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 11736 exited with code -6, but exit code -30 is expected

======================================================================
FAIL: test_specify_environment (test.test_posix.TestPosixSpawnP.test_specify_environment)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1822, in test_specify_environment
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 28506 exited with code -6, but exit code 0 is expected

----------------------------------------------------------------------
Ran 43 tests in 2.545s

FAILED (failures=21, skipped=6)
Warning -- files was modified by test_posix
Warning -- Before: []
Warning -- After: ['python.core']
test test_posix failed
0:00:02 load avg: 0.17 [1/1/1] test_posix failed (21 failures)

== Tests result: FAILURE ==

1 test failed:
 test_posix

Total duration: 2.7 sec
Total tests: run=43 (filtered) failures=21 skipped=6
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

CPython versions tested on:

CPython main branch, 3.14

Operating systems tested on:

Other

Linked PRs

• gh-131624: Fix posix_spawn tests failing on NetBSD with stack limit assertions #131625

[furkanonder]

bisect to #130398 CC: @markshannon

[vstinner]

Extract of the assertion error:

assertion "here_addr < _tstate->c_stack_top" failed:
file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"

Can you dump guard_size, stack_addr, stack_size and here_addr values in _Py_InitializeRecursionLimits()? Example:

diff --git a/Python/ceval.c b/Python/ceval.c
index 363f263ad2a..eb5436991e0 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -464,6 +464,7 @@ _Py_InitializeRecursionLimits(PyThreadState *tstate)
 _tstate->c_stack_soft_limit = base + PYOS_STACK_MARGIN_BYTES * 2;
 #endif
 _tstate->c_stack_hard_limit = base + PYOS_STACK_MARGIN_BYTES;
+fprintf(stderr, "@@@ stack_size=%zu, guard_size=%zu, stack_addr=%p, here_addr=%p\n", stack_size, guard_size, stack_addr, (void*)here_addr);
 assert(_tstate->c_stack_soft_limit < here_addr);
 assert(here_addr < _tstate->c_stack_top);
 return;

[furkanonder]

Extract of the assertion error:

assertion "here_addr < _tstate->c_stack_top" failed:
file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"

Can you dump guard_size, stack_addr, stack_size and here_addr values in _Py_InitializeRecursionLimits()? Example:

diff --git a/Python/ceval.c b/Python/ceval.c
index 363f263ad2a..eb5436991e0 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -464,6 +464,7 @@ _Py_InitializeRecursionLimits(PyThreadState tstate)
_tstate->c_stack_soft_limit = base + PYOS_STACK_MARGIN_BYTES * 2;
#endif
_tstate->c_stack_hard_limit = base + PYOS_STACK_MARGIN_BYTES;
+fprintf(stderr, "@@@ stack_size=%zu, guard_size=%zu, stack_addr=%p, here_addr=%p\n", stack_size, guard_size, stack_addr, (void)here_addr);
assert(_tstate->c_stack_soft_limit < here_addr);
assert(here_addr < _tstate->c_stack_top);
return;

╰─$ ./python -m test test_posix -m TestPosixSpawn -m TestPosixSpawnP -v
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff7bb000, here_addr=0x7f7fffbb8240
== CPython 3.14.0a6+ (heads/main-dirty:a1232459860, Mar 25 2025, 19:00:35) [GCC 10.5.0]
== NetBSD-10.0-amd64-x86_64-64bit-ELF little-endian
== Python build: debug
== cwd: /home/blue/cpython/build/test_python_worker_12945æ
== CPU count: 16
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests

Using random seed: 692812059
0:00:00 load avg: 3.16 Run 1 test sequentially in a single process
0:00:00 load avg: 3.16 [1/1] test_posix
test_bad_file_actions (test.test_posix.TestPosixSpawn.test_bad_file_actions) ... ok
test_close_file (test.test_posix.TestPosixSpawn.test_close_file) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fff4887d0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_dup2 (test.test_posix.TestPosixSpawn.test_dup2) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fff618f10
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_empty_file_actions (test.test_posix.TestPosixSpawn.test_empty_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fffbed3e0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_multiple_file_actions (test.test_posix.TestPosixSpawn.test_multiple_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fff6dcc70
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_no_such_executable (test.test_posix.TestPosixSpawn.test_no_such_executable) ... ok
test_none_file_actions (test.test_posix.TestPosixSpawn.test_none_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fffb67330
ok
test_open_file (test.test_posix.TestPosixSpawn.test_open_file) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fffd0c500
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_resetids (test.test_posix.TestPosixSpawn.test_resetids) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff8e2c20
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_resetids_explicit_default (test.test_posix.TestPosixSpawn.test_resetids_explicit_default) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fffb71de0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_returns_pid (test.test_posix.TestPosixSpawn.test_returns_pid) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff03be60
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup (test.test_posix.TestPosixSpawn.test_setpgroup) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff406e70
ok
test_setpgroup_wrong_type (test.test_posix.TestPosixSpawn.test_setpgroup_wrong_type) ... ok
test_setscheduler_only_param (test.test_posix.TestPosixSpawn.test_setscheduler_only_param) ... skipped 'bpo-34685: test can fail on BSD'
test_setscheduler_with_policy (test.test_posix.TestPosixSpawn.test_setscheduler_with_policy) ... skipped 'bpo-34685: test can fail on BSD'
test_setsid (test.test_posix.TestPosixSpawn.test_setsid) ... skipped "setsid is not supported: NotImplementedError('posix_spawn: setsid unavailable on this platform')"
test_setsigdef (test.test_posix.TestPosixSpawn.test_setsigdef) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff9d7890
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_setsigdef_wrong_type (test.test_posix.TestPosixSpawn.test_setsigdef_wrong_type) ... ok
test_setsigmask (test.test_posix.TestPosixSpawn.test_setsigmask) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff482bf0
ok
test_setsigmask_wrong_type (test.test_posix.TestPosixSpawn.test_setsigmask_wrong_type) ... ok
test_specify_environment (test.test_posix.TestPosixSpawn.test_specify_environment) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fffb77ac0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_bad_file_actions (test.test_posix.TestPosixSpawnP.test_bad_file_actions) ... ok
test_close_file (test.test_posix.TestPosixSpawnP.test_close_file) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffefd8000, here_addr=0x7f7fff1aee60
ok
test_dup2 (test.test_posix.TestPosixSpawnP.test_dup2) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff079000, here_addr=0x7f7fff2191f0
ok
test_empty_file_actions (test.test_posix.TestPosixSpawnP.test_empty_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff079000, here_addr=0x7f7fff63a300
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_multiple_file_actions (test.test_posix.TestPosixSpawnP.test_multiple_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff079000, here_addr=0x7f7ffffc09f0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_no_such_executable (test.test_posix.TestPosixSpawnP.test_no_such_executable) ... ok
test_none_file_actions (test.test_posix.TestPosixSpawnP.test_none_file_actions) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff079000, here_addr=0x7f7fff998ee0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_open_file (test.test_posix.TestPosixSpawnP.test_open_file) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff079000, here_addr=0x7f7fffc34930
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_posix_spawnp (test.test_posix.TestPosixSpawnP.test_posix_spawnp) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff673000, here_addr=0x7f7fffa704e0
ok
test_resetids (test.test_posix.TestPosixSpawnP.test_resetids) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fffebbbd0
ok
test_resetids_explicit_default (test.test_posix.TestPosixSpawnP.test_resetids_explicit_default) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fff604700
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_returns_pid (test.test_posix.TestPosixSpawnP.test_returns_pid) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fff794ad0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup (test.test_posix.TestPosixSpawnP.test_setpgroup) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fff40dda0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL
test_setpgroup_wrong_type (test.test_posix.TestPosixSpawnP.test_setpgroup_wrong_type) ... ok
test_setscheduler_only_param (test.test_posix.TestPosixSpawnP.test_setscheduler_only_param) ... skipped 'bpo-34685: test can fail on BSD'
test_setscheduler_with_policy (test.test_posix.TestPosixSpawnP.test_setscheduler_with_policy) ... skipped 'bpo-34685: test can fail on BSD'
test_setsid (test.test_posix.TestPosixSpawnP.test_setsid) ... skipped "setsid is not supported: NotImplementedError('posix_spawnp: setsid unavailable on this platform')"
test_setsigdef (test.test_posix.TestPosixSpawnP.test_setsigdef) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7ffff2bac0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
FAIL
test_setsigdef_wrong_type (test.test_posix.TestPosixSpawnP.test_setsigdef_wrong_type) ... ok
test_setsigmask (test.test_posix.TestPosixSpawnP.test_setsigmask) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fffe9e820
ok
test_setsigmask_wrong_type (test.test_posix.TestPosixSpawnP.test_setsigmask_wrong_type) ... ok
test_specify_environment (test.test_posix.TestPosixSpawnP.test_specify_environment) ... @@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff9c9000, here_addr=0x7f7fff36bbd0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
FAIL

======================================================================
FAIL: test_close_file (test.test_posix.TestPosixSpawn.test_close_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2087, in test_close_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 5945 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_dup2 (test.test_posix.TestPosixSpawn.test_dup2)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2105, in test_dup2
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 1255 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_empty_file_actions (test.test_posix.TestPosixSpawn.test_empty_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1842, in test_empty_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 9865 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_multiple_file_actions (test.test_posix.TestPosixSpawn.test_multiple_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2021, in test_multiple_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 26380 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_open_file (test.test_posix.TestPosixSpawn.test_open_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2068, in test_open_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 23922 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids (test.test_posix.TestPosixSpawn.test_resetids)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1860, in test_resetids
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 29780 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids_explicit_default (test.test_posix.TestPosixSpawn.test_resetids_explicit_default)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1851, in test_resetids_explicit_default
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 4181 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_returns_pid (test.test_posix.TestPosixSpawn.test_returns_pid)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1792, in test_returns_pid
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 9818 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setsigdef (test.test_posix.TestPosixSpawn.test_setsigdef)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1955, in test_setsigdef
 support.wait_process(pid, exitcode=-signal.SIGUSR1)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 21767 exited with code -6, but exit code -30 is expected

======================================================================
FAIL: test_specify_environment (test.test_posix.TestPosixSpawn.test_specify_environment)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1822, in test_specify_environment
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 16068 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_empty_file_actions (test.test_posix.TestPosixSpawnP.test_empty_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1842, in test_empty_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 1453 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_multiple_file_actions (test.test_posix.TestPosixSpawnP.test_multiple_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2021, in test_multiple_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 15889 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_none_file_actions (test.test_posix.TestPosixSpawnP.test_none_file_actions)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1833, in test_none_file_actions
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 4565 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_open_file (test.test_posix.TestPosixSpawnP.test_open_file)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 2068, in test_open_file
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 2565 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_resetids_explicit_default (test.test_posix.TestPosixSpawnP.test_resetids_explicit_default)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1851, in test_resetids_explicit_default
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 27585 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_returns_pid (test.test_posix.TestPosixSpawnP.test_returns_pid)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1792, in test_returns_pid
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 1509 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setpgroup (test.test_posix.TestPosixSpawnP.test_setpgroup)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1869, in test_setpgroup
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 19011 exited with code -6, but exit code 0 is expected

======================================================================
FAIL: test_setsigdef (test.test_posix.TestPosixSpawnP.test_setsigdef)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1955, in test_setsigdef
 support.wait_process(pid, exitcode=-signal.SIGUSR1)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 22118 exited with code -6, but exit code -30 is expected

======================================================================
FAIL: test_specify_environment (test.test_posix.TestPosixSpawnP.test_specify_environment)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_posix.py", line 1822, in test_specify_environment
 support.wait_process(pid, exitcode=0)
 ~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
 File "/home/blue/cpython/Lib/test/support/__init__.py", line 2241, in wait_process
 raise AssertionError(f"process {pid} exited with code {exitcode2}, "
 f"but exit code {exitcode} is expected")
AssertionError: process 4931 exited with code -6, but exit code 0 is expected

----------------------------------------------------------------------
Ran 43 tests in 3.160s

FAILED (failures=19, skipped=6)
Warning -- files was modified by test_posix
Warning -- Before: []
Warning -- After: ['python.core']
test test_posix failed
0:00:03 load avg: 3.16 [1/1/1] test_posix failed (19 failures)

== Tests result: FAILURE ==

1 test failed:
 test_posix

Total duration: 3.7 sec
Total tests: run=43 (filtered) failures=19 skipped=6
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

without verbose;

╰─$ ./python -m test test_posix -m TestPosixSpawn -m TestPosixSpawnP
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff0b0000, here_addr=0x7f7fff4ada60
Using random seed: 400541714
0:00:00 load avg: 1.07 Run 1 test sequentially in a single process
0:00:00 load avg: 1.07 [1/1] test_posix
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff63b000, here_addr=0x7f7fff5c7cd0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff7fe000, here_addr=0x7f7fff303be0
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffadbf50
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff793140
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffcffa70
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffc57eb0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff7418b0
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff30f920
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffa98760
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffe09510
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffa21cb0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffc60980
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff1f6a70
assertion "_tstate->c_stack_soft_limit < here_addr" failed: file "Python/ceval.c", line 468, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff89ee90
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7ffff64d40
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffc23700
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fff65a3a0
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffe7e6a0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff442000, here_addr=0x7f7fffa3e370
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff23c000, here_addr=0x7f7fff6390a0
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fff7c1640
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fff4624c0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fffe61a90
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fff45b8e0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fff682690
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fffe66900
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
@@@ stack_size=4194304, guard_size=1048576, stack_addr=0x7f7ffed89000, here_addr=0x7f7fffc383c0
assertion "here_addr < _tstate->c_stack_top" failed: file "Python/ceval.c", line 469, function "_Py_InitializeRecursionLimits"
Warning -- files was modified by test_posix
Warning -- Before: []
Warning -- After: ['posix_spawnp_tes.core', 'python.core']
test test_posix failed -- multiple errors occurred; run in verbose mode for details
0:00:02 load avg: 1.07 [1/1/1] test_posix failed (23 failures)

== Tests result: FAILURE ==

1 test failed:
 test_posix

Total duration: 2.7 sec
Total tests: run=43 (filtered) failures=23 skipped=6
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

[vstinner]

stack_size=4194304, guard_size=1048576, stack_addr=0x7f7fff6b2000, here_addr=0x7f7fff6dcc70

guard_size is quite big, it's 1 MiB.

>>> stack_addr = 0x7f7fff6b2000
>>> here_addr = 0x7f7fff6dcc70
>>> guard_size=1048576
>>> base = stack_addr + guard_size
>>> c_stack_soft_limit = base + 4096*8 * 2
>>> c_stack_soft_limit < here_addr
False

[serhiy-storchaka]

Would changing the value of PYOS_STACK_MARGIN help?

[serhiy-storchaka]

No, changing PYOS_STACK_MARGIN does not help.

The difference between here_addr and base varies in a wide range -- from about -5_000_000 to 15_000_000. It can be negative or exceed stack_size by far. stack_addr is often repeated from test to test, but here_addr varies in a wide range. If any of these values was completely random, we would expect a wider ranger (in full 64 bits), so there must be some relation between them, but it differs from expected.

Note that there was a bug in handling the guard area which was fixed only recently (see https://gnats.netbsd.org/57721). It is possible that there are other bugs left.

In any case, until we find the root of the issue (being it our misuse or the NetBSD bug), PR #131625 looks like a correct workaround.