glibc detected *** python: corrupted double-linked list

David Cournapeau cournape at
Wed Feb 25 08:06:37 EST 2009

On Wed, Feb 25, 2009 at 9:40 PM, Christian Meesters <meesters at> wrote:
> Hoi,
> I have a problem using my software on my 64bit laptop, after an update of
> my system. The same code still runs on 32bit Intel, but on my laptop I
> provoke the crash in the title. The crash is caused - as narrowed down by
> me - by returning a static PyObject from a C-extension function.

Those errors are caused by writing in an invalid pointer, but not far
enough to cause a direct segfault - just enough to corrupt core data
structures of the runtime :)

> Well, now I wondering what to do? A web search delivered no relevant bug
> reports about glibc on my system (the recent Ubuntu 8.10). Is there a
> source for validated glibc for x86_64? Oh, and I'm using Ubuntu's ready-
> made Python package, version 2.5.2..

It is very unlikely the problem is in glibc - I would check your code
carefully first :) On Linux, the following are useful:
 - first, try to compile with as many warning flags as possible (-W
-Wall -Wextra is a pretty good baseline)
 - then, if you have a small reproducible crash, run the extension
under valgrind after having built the extension with -g. This will
give you more informations.
 - if the above does not help, using gdb can help too.

If the program works in 32 but not in 64, there are several things to
look at (long is 8 bytes, not 4 on Linux, so some long -> int
convertion may be broken). Sometimes, the program just happens to work
on 32 bits, but by accident (running valgrind on both 32 and 64 bits
may be helpful too).



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