Wireshark · Ethereal-dev: Re: [Ethereal-dev] help: new dissector debugging questions

[Richard van der Hoff <richard@xxxxxxxxxxxxxxxxxx>]

Wei Li (Michael) wrote:
> Hi, There is sth weird when I am debugging a new dissector in 
> Ethereal. During debugging, the execution order of program statements
>  is not following the program flow. For example, in the following 
> capture of debugging session, it jumpped around the statement 2105 
> quite a few times until finally execute it. I have never met such 
> problems with GDB.

That's because the code's been optimised by the compiler and is no
longer in the same order as the source.

Try rerunning configure with

CFLAGS=-O0 ./configure [options]

and rebuild.

> By the way, after I successfully dissect the first two packets in the
>  dump file, the program suddenly aborted because of failing on the 
> following assertion: ** ERROR **: file tvbuff.c: line 379 
> (check_offset_length_no_exception): assertion failed: 
> (tvb->initialized). Could anybody help me out here?

Er, you passed the tvbuff routines an uninitialised tvbuff?

> When I trace step by step into the major routine dissect_protoname( 
> ), the (proto_tree * tree) changed to NULL one step into the routine 
> while the passed-in argument is not NULL. Besides, the pinfo->cinfo 
> pointer changed to NULL after I call asn1_open( ) method.

Again, sounds like it may be due to optimisation and may go away when
you disable optimisation.

> If possible, can someone give me a link about the whole architecture
> of Ethereal, the sequence diagram, or the call flow or something like
> that.

I take it you've read doc/README.developer?

Richard