Bugs item #1241545, was opened at 2005-07-20 06:27 Message generated for change (Comment added) made by nnorwitz You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1241545&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: Python 2.3 Status: Open Resolution: None Priority: 5 Submitted By: munder12 (munder12) Assigned to: Nobody/Anonymous (nobody) Summary: garbage collection asserts failing Initial Comment: Modules/gcmodule.c:294: visit_reachable: Assertion `gc_refs > 0 || gc_refs == (-3) || gc_refs == (-2)' failed. Running Python 2.3.4 on Fedora Core 3 (2.6.11-1.35_FC3smp). Also tried Python 2.3.5. When searching Google for this error, found following link where someone using yum updates was getting same error from python http://forums.fedoraforum.org/showthread.php?t=54704 ---------------------------------------------------------------------- >Comment By: Neal Norwitz (nnorwitz) Date: 2005-10-03 22:13 Message: Logged In: YES user_id=33168 munder, do you think this is still a bug or should it be closed? ---------------------------------------------------------------------- Comment By: munder12 (munder12) Date: 2005-07-25 05:55 Message: Logged In: YES user_id=1156202 Well, I have what appears to be a working solution: Use python 2.5a0 from CVS. This version works with psyco. I suspect the bug fix to gcmodules.c that added the missing INCREF is the culprit (the one labelled as a backport candidate). As for why the assert was triggering, I have my thoughts. First, gdb when trying to read the core files was confirming the absolute path to the (non-debug) executable I thought I was running but also would not give a valid traceback due to stack corruption. Is it possible that the memory corruption was making it where (__ASSERT_VOID_CAST (0)) was unable to succeed? (This is what assert(expr) is macro'd to when defining NDEBUG.) Thanks. ---------------------------------------------------------------------- Comment By: Tim Peters (tim_one) Date: 2005-07-21 11:25 Message: Logged In: YES user_id=31435 This part of the command line you showed: -DNDEBUG causes C's assert() macro to "expand to nothing". That's part of the definition of the C language, not a Python convention. So if you compiled Python with -DNDEBUG, and are seeing an assert() trigger, then I can only conclude one of two things: 1. Your C compiler has a very bad bug. or 2. You're not actually using the Python you think you're using. That said, I've seen very strange bugs triggered by psyco too, but not even psyco can cause code to execute that doesn't exist. No code is generated for an assert() when compiling with -DNDEBUG: the C preprocessor throws assert()s away when NDEBUG is #define'd. ---------------------------------------------------------------------- Comment By: munder12 (munder12) Date: 2005-07-21 11:05 Message: Logged In: YES user_id=1156202 Well, this gets even stranger. I am not running a debug version of python as far as I can tell. I built 2.4.1 in a fresh directory by: ./configure --prefix=/blah make make test make install The gcmodule was echo'd as being built this way: gcc -pthread -c -fno-strict-aliasing -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I. -I./Include -DPy_BUILD_CORE -o Modules/gcmodule.o Modules/gcmodule.c I am leaning toward psyco as being the culprit based on your suggestions since it is the only one that has extra C libraries. I'm running the case with Tkinter, pyro, and psyco all not being imported. Thanks again, Mark ---------------------------------------------------------------------- Comment By: Tim Peters (tim_one) Date: 2005-07-20 17:35 Message: Logged In: YES user_id=31435 I'm intimately familiar with the gc code, and I'm sure this assert has never triggered in any core Python release, or in any Zope release, not even in between-releases buggy development states. It means some memory gc is staring at has an insane value, one that can't possibly arise in intended operation. If you get into gdb (whatever debugger you have), it might be useful to know what value gc_refs _does_ have at this point. One possibility is that you're mixing a debug-build Python (which you are using: asserts never trigger in a release-build Python, simply because the assert() macro expands to nothing then) with one or more release-build extension modules. Trying to mix like that can blow up in all sorts of "impossible" ways. ---------------------------------------------------------------------- Comment By: munder12 (munder12) Date: 2005-07-20 17:04 Message: Logged In: YES user_id=1156202 Sorry, I realize it is not much to go on but I cannot currently get it to fail other than when I run this one script. It is all written in python. It is a simulation running a genetic algorithm that is set up to run about 24 hours straight. This error occurs within about 5 hours into the simulation (repeatedly). Running similar simulations that complete in less than a couple hours run without a problem. Was hoping someone familiar with the gc routines might go "oh, yeah... -4 is valid now too.." or something similar. In the meantime, I will be trying to continue to reduce the number of imported modules where I can still get the problem to happen There are 2 modules psyco and pyro that are non- core and Tkinter. But since the Google search turned up yum giving same error (which I doubt uses psyco, pyro, or Tkinter), I thought I would mention it here as I continued searching. ---------------------------------------------------------------------- Comment By: Tim Peters (tim_one) Date: 2005-07-20 14:24 Message: Logged In: YES user_id=31435 Well, this isn't enough info to go on. For example, what program was Python running at the time? What were you doing? How could anyone else try to reproduce this? It's certainly not something Python normally does ;-) FWIW, the most likely cause is bad C coding in a Python extension (non-core) module. That the problem persists for you across Python versions points even more at non-core C code. ---------------------------------------------------------------------- Comment By: Neil Schemenauer (nascheme) Date: 2005-07-20 14:20 Message: Logged In: YES user_id=35752 Usually this kind of error is caused by a bug in a 3rd party extension module. Try to narrow down the test case as much as possible. Can you provide a Python script that triggers the assertion failure? ---------------------------------------------------------------------- Comment By: munder12 (munder12) Date: 2005-07-20 14:15 Message: Logged In: YES user_id=1156202 This also fails in Python 2.4.1 on same system. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1241545&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
