RE: [xml] Problem with basic libxml functions

[Jesse Pelton <jsp PKC com>]

You need to understand how XML handles whitespace; see
http://www.w3.org/TR/2004/REC-xml-20040204/.  The text node to which Bill is
referring is the whitespace (newline + space characters) that you've used to
format your document. 

<terminal_preference>
</terminal_preference>

is not equivalent to

<terminal_preference></terminal_preference>

or

<terminal_preference/>

unless you provide a DTD the indicates the whitespace should be ignored.

I imagine the code you've snipped assumes child_of_cur points to a list of
children, but text node have no children.

> -----Original Message-----
> From: William M. Brack [mailto:wbrack mmm com hk] 
> Sent: Sunday, March 21, 2004 6:15 AM
> To: Sagar Rastogi
> Cc: xml gnome org
> Subject: Re: [xml] Problem with basic libxml functions
>
>
> Sagar Rastogi said:
> > Hi
> Hi Sagar
>
> >        I am working on an enhancement to make the panel-run-dialog
> > "smart", i.e. it should be able to remember whether the user wanted
> > to run
> > a command in terminal or not. So next time the user runs the same
> > command,
> > his preference is remembered. (Bug no. 77300).
> >     I am storing the data in an xml file in the foll. format
> >
> > <?xml version="1.0"?>
> > <terminal_preference>
> >         <command>
> >                 <name> Program name like "galeon" or "nautilus"
> > </name>
> >                 <terminal> true or false </terminal>
> >         </command>
> >         <command>
> >                 ...
> >         </command>
> > </terminal_preference>
> >
> > I am using libxml functions to parse/write to the xml file. I have
> > used
> > them exactly in the way specified in examples. Foll is a code
> > extract:
> >
> > <snip>
> >
> >     //cur points to root node at the start.
> >     cur = cur->xmlChildrenNode;
> >         printf("Reaches here 3.2 \n");  //This gets printed
> >         //cur points to command
> >         while(cur) {
> >                 printf("Reaches here 3.3 \n"); //This gets printed
> >                 child_of_cur = cur->xmlChildrenNode;
> >
> > <snip>
>
> Ah, a most unfortunate spot to "snip"... I can see what you have
> done with the variable "child_of_cur", but I have absolutely no way
> to tell what you do in the following lines with it or with the
> variable "cur".  Certainly the cause of your "crash" is not on these
> specific lines of code, but probably somewhere later in the loop.
>
> > The contents of my xml file are:
> >
> > <?xml version="1.0"?>
> > <terminal_preference>
> > </terminal_preference>
> >
> >     As is obvious from the code extract, the control enters 
> the while
> > loop
> > when it shouldn't. The program crashes at the line:
>
> Hmmm... well, it's not obvious to *me* why it shouldn't enter the
> while loop.  Your element <terminal_preference> looks to me like it
> has text content which will be a child node, so I would expect it to
> enter the loop.
>
> >  child_of_cur = cur->xmlChildrenNode
> >     Could somebody please tell me what is the error here?
> >
> > Regards
> > Sagar Rastogi
>
> I heartily recommend to you that you learn to use the gdb debugger,
> and step through your code.  That should help you to see where you
> are going wrong.
>
> Bill
>
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