From: Simon Strandgaard <0bz63fz3m1qt3001@...>
Date: 2003-04-29T05:44:23+09:00
Subject: Re: c++/ruby debugging advices

On Mon, 28 Apr 2003 15:55:10 +0000, Lyle Johnson wrote:

> Simon Strandgaard wrote:
> 
>> There must be others than me who is mixing c++ & ruby.
>> When bad things happens, How do you debug it?
> 
> Many of the problems I seem to run into when mixing C++ and Ruby have to 
> do with Ruby objects being garbage-collected before I expect them to be 
> (because of errors in my code). Or, alternately, Ruby continuing to use 
> objects that contain pointers to C++ objects that have already been 
> destroyed without Ruby's knowledge.

Right now I only have *one* instance in c++ of a ruby-class. 
I keep track of such global objects in an Array. 
You can see how this is working here:
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/metaeditor/source3/backend/source/rubycpp.cpp?rev=1.2&only_with_tag=MAIN&content-type=text/vnd.viewcvs-markup

A guru-review of this code would be nice :-)
This information will end up in the embedding tutorial im working on.


> So one way to try to debug this is to add lots of (temporary) print 
> statements in your code, to trace exactly when and where objects are 
> being created and destroyed. For this to be effective, you of course 
> need to have a clear understanding in your mind of what you would expect 
> to see, if the program's working properly ;)

Agree.. I use this technique all the time.


> Another thing you could try is to use a memory debugging tool. If you're 
> running Linux, I really recommend Valgrind.

In order to hunt down this problem I tried using ElectricFence. 
But no illegal-memory-acesses occur. It still segfaults the same place. 

What information do you need from me in order to 
help locating where the problem is ?


ElectricFence vs Valgrind... what is the difference ?

--
Simon Strandgaard