Re: [xml] Debugging memory allocation failures...

[Daniel Veillard <veillard redhat com>]

On Wed, Oct 20, 2004 at 05:18:42PM -0700, Nathanael Noblet wrote:
> Hello
>       So I'm playing around a little with libxml and Apache modules. I 
>       have a program that I tested out and now I'm playing with it through Apache 
> modules. It doesn't quite work. I've done a little debugging by 
> printing where I was and some of the elements... Here's what I've done:
>
> I have a generic apache module template created from apxs. It prints 
> out a string. or multiple strings. At first what I tried was taking my 
> program and calling it from the apache handler function. Partially 
> worked. I wanted to use the xmlDocDumpMemory() to get a handle on the 
> assembled xml. I always get a null for the xmlChar **out_buffer. So I 
> thought perhaps it had something to do with memory allocation of libxml 
> conflicting with memory allocation of apache or apr or whatever. but 
> when I do the first parse of xmlReadMemory() the doc isn't null. and I 
> can use a modified version of print_element_names() to print out to the 
> browser the xml element names and attributes etc...
>
>       So how come I can use libxml from my module, but xmlDocDumpMemory 
> fails? How can I tell why it failed? Ideas etc...?

  First read this if not already done:
    http://xmlsoft.org/xmlmem.html
You can provide your own memory allocator and use this for debugging,
but I would suggest to run apache under a debugger as a single server
put a breakpoint in the xmlDocDumpMemory and make a request triggering
it, then check what's happening. You can waste a lot of time if you
don't use the debugger approach.

Daniel

-- 
Daniel Veillard      | Red Hat Desktop team http://redhat.com/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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