free(): invalid pointer on import pytave

[David Grundberg]

Hello David,
Sorry to bother you, but something awkward happens when I try :
"import pytave "
in Python:
I always get:

free(): invalid pointer: 0xb72e1930

and I never had problems with Octave (3.2.4) or Python (2.6.5 (r265:79063, Jul 5 2010)), gcc 4.5 on OpenSuse 11.3
And the pytave installation went well.

I welcome any help,
(name removed)

[David Grundberg (individ)]

I need more information. Which revision of Pytave are you running?

The pointer will change between runs because of a feature in the kernel, so the address by itself is useless. I'll need you to make a backtrace, that way I'll be able to help you.

Please run python through gdb. Install the debugging symbols for Python first (there's usually a separate package for that, I don't know the details of Suse).

1. gdb `which python`
2. run
3. import pytave
4. With some luck you get a segfault (you do get a segfault/abort right?). Gdb will then prompt.
5. Write bt full for a backtrace. That listing is most useful in finding the error.

Also make sure that you are running pytave in the same python interpreter that it were linked against.

[Liviu Vladutu (liviu-vladutu)]

First of all, thanks for the fast reply.
Here are the answers:
A. - I run the latest pytave (from 11th of September);

B. When I do 'run' after (gdb python)
I get :
1) warning: the debug information found in "/usr/lib/debug//lib/libc-2.11.2.so.debug" does not match "/lib/libc.so.6" (CRC mismatch)
and:

2) Missing separate debuginfo for /lib/libc.so.6
Try: zypper install -C "debuginfo(build-id)=f71a3d8772eda244959bac3385b43c719b8ca227"

This latter command, 2) ends with "Nothing to do."

C. After that, import pytave starts with any other error /warning except:
glibc detected *** /usr/bin/python: free(): invalid pointer:

but gdb behaves better (now, it can be interrupted), showing an answer to 'bt' like the attached one.

Thank you in advance.

[David Grundberg (individ)]

The backtrace is a mess. Somehow something breaks while loading the GNU Octave m-files? During a delete on an octave-base-value object? I don't know where to begin on this one.

Looking at what you got that time before this:
free(): invalid pointer: 0xb72e1930
Hm. 0xb7....? That's a pointer to something dangerously close to the stack. What is it doing inside a free call? Am I missing something?

I'd say try running octave-tip or the testing version. I don't recognize this specific error, but 3.2.4 is 8 months old. Many things have been fixed and I don't remember them all.

[Liviu Vladutu (liviu-vladutu)]

Indeed, with the new, testing version of octave it works well. Thank you again.

[David Grundberg (individ)]

Glad to hear you got it working. Happy hacking!