On 23-11-2021 13:07, Arnaud Loonstra wrote:
Hi,
I've got Python embedded successfully in a program up until now as I'm
now running into weird GC related segfaults. I'm currently trying to
debug this but my understanding of CPython limits me here.
I'm creating a Tuple in C but it crashes on creating it after a while.
It doesn't make sense which makes me wonder something else must be
happening? Could be it just crashes here because the GC is cleaning up
stuff completely unrelated to the allocation of the new tuple? How can I
troubleshoot this?
I've got CPython compiled with --with-valgrind --without-pymalloc
--with-pydebug
In C I'm creating a tuple with the following method:
static PyObject *
s_py_zosc_tuple(pythonactor_t *self, zosc_t *oscmsg)
{
assert(self);
assert(oscmsg);
char *format = zosc_format(oscmsg);
PyObject *rettuple = PyTuple_New((Py_ssize_t) strlen(format) );
It segfaults here (frame 16) after 320 times (consistently)
1 __GI_raise raise.c 49 0x7ffff72c4e71
2 __GI_abort abort.c 79 0x7ffff72ae536
3 fatal_error pylifecycle.c 2183 0x7ffff7d84b4f
4 Py_FatalError pylifecycle.c 2193 0x7ffff7d878b2
5 _PyObject_AssertFailed object.c 2200 0x7ffff7c93cf2
6 visit_decref gcmodule.c 378 0x7ffff7dadfd5
7 tupletraverse tupleobject.c 623 0x7ffff7ca3e81
8 subtract_refs gcmodule.c 406 0x7ffff7dad340
9 collect gcmodule.c 1054 0x7ffff7dae838
10 collect_with_callback gcmodule.c 1240 0x7ffff7daf17b
11 collect_generations gcmodule.c 1262 0x7ffff7daf3f6
12 _PyObject_GC_Alloc gcmodule.c 1977 0x7ffff7daf4f2
13 _PyObject_GC_Malloc gcmodule.c 1987 0x7ffff7dafebc
14 _PyObject_GC_NewVar gcmodule.c 2016 0x7ffff7daffa5
15 PyTuple_New tupleobject.c 118 0x7ffff7ca4da7
16 s_py_zosc_tuple pythonactor.c 366 0x55555568cc82
17 pythonactor_socket pythonactor.c 664 0x55555568dac7
18 pythonactor_handle_msg pythonactor.c 862 0x55555568e472
19 pythonactor_handler pythonactor.c 828 0x55555568e2e2
20 sphactor_actor_run sphactor_actor.c 855 0x5555558cb268
... <More>
Any pointer really appreciated.
I've found enabling PYTHONTRACEMALLOC=1 in the environment gives me a
pointer to where to offending block was allocated.
I'm calling this method from C:
18 def handleSocket(self, addr, data, type, name, uuid):
19 if addr == "/pulse":
20 self.lampval += 1
21 return (addr, [0,0])
Modules/gcmodule.c:108: gc_decref: Assertion "gc_get_refs(g) > 0"
failed: refcount is too small
Memory block allocated at (most recent call first):
File "/home/arnaud/src/build-gazebosc-Desktop-Debug/bin/lampen.py",
line 21
object address : 0x7fffd81154c0
object refcount : 1
object type : 0x7ffff7f3df20
object type name: list
object repr : [117, 0]
Fatal Python error: _PyObject_AssertFailed
Python runtime state: initialized
Current thread 0x00007ffff2481640 (most recent call first):
File "/home/arnaud/src/build-gazebosc-Desktop-Debug/bin/lampen.py",
line 21 in handleSocket
Thread 0x00007ffff5d288c0 (most recent call first):
<no Python frame>
Now it clearly says the refcount is 1 so I'm puzzling what it means?
Rg,
Arnaud
--
https://mail.python.org/mailman/listinfo/python-list
