My C module crashes

[Egil Moeller]

Hi!

I've written a C-module for Python, and it works as intended, but
obviously does something wrong with its memmory management (refference
counting), as it causes Python to segfault now and then (randomly,
whey :S)

The module source code is available at
http://grimoire.takeit.se/files/CReader.c

The code isn't _that_ long, so someone experienced with writing Python C
modules should probably not have that hard a time finding what I do
wrong :)

Thanks in advance,
Egil Möller

[Daniel Dittmar]

Egil Moeller wrote:

I've written a C-module for Python, and it works as intended, but
obviously does something wrong with its memmory management (refference
counting), as it causes Python to segfault now and then (randomly,
whey :S)

You can atry to use the Python function sys.getrefcount. Print the
refcount of the parameter values before and after your extension gets
called and print the refcount of the return value (s). I once forgot to
increment the refcount of the None object which was put into the return
tuple.

If you pass a list as a parameter, you should also print the refcounts
of the list elements etc.

Daniel Dittmar

[John Machin]

Egil Moeller wrote:

Hi!

I've written a C-module for Python, and it works as intended, but
obviously does something wrong with its memmory management (refference counting), as it causes Python to segfault now and then (randomly,
whey :S)

The module source code is available at
http://grimoire.takeit.se/files/CReader.c

The code isn't _that_ long, so someone experienced with writing Python C modules should probably not have that hard a time finding what I do
wrong :)

What you are doing wrong:

1. Unless getting the source to/from a web page has stuffed up the
indentation [which you should have checked before posting your
message], it appears to be indented only ONE space per level. Are you
using tabs? Don't. They are intrinsically evil.

2. Your code's over 1200 lines long, and even after allowing for the
indentation problem it certainly doesn't read like the poetry of your
namesake, Skalla-Grim's son.

3. Expecting people to debug your code remotely when it exhibits
problems (1) and (2)

4. Not stating what (if anything) you have tried yourself before
posting.

5. Using system free() and realloc() instead the Python-supplied memory
API functions.

6. Using *ANY* free() or realloc() function on memory that has *NOT*
been allocated with the allocator function from the same family.

7. Not checking whether a buffer has even been allocated before trying
to deallocate it.

[Dima Dorfman]

On 2005-02-28, Egil Moeller <re****@takeit.se> wrote:

I've written a C-module for Python, and it works as intended, but
obviously does something wrong with its memmory management (refference
counting), as it causes Python to segfault now and then (randomly,
whey :S)

Have you tried compiling Python and your module with debugging
enabled? It might make the crash less random--or it might not help at
all, but it's probably worth a try. Running Python with debugging
enabled is a good idea anyway when developing extension modules.