Re: Debugging Gimp plugins

[lduperval at sprint dot ca]

On  8 Feb, Keith Seitz wrote:
> lduperval@sprint.ca wrote:
>> 
>> Hi,
>> 
>> If anyone has experience successfully debugging gimp plugins with
>> insight, please drop me a line. I can't figure out the proper way to do
>> it yet.
>> 
>> L
> 
> I don't know much about the Gimp (gasp!),

Hhhhhhhhhh!! Shame! Shame! :-)

> but I assume that it's plugins
> are just loadable modules (almost identical to shared libraries).
> 

I don't think so. I've looked at the source and it seems to be
socket-based. It looks like the plugin is a standalone program that
communicates with GIMP using sockets. But don't take my word for it.

So my situation is that I'm trying to write a Tcl-based extension (or at
least make an old one work with the new GIMP). It requires running a new
wish process. That wish process loads a dynamic module. And there are
some dependencies on shared libs also. I find it to be a debugging mess
but I thing it would be an even bigger mess for me to try to compile a
monolithic binary containing the Tcl, Tk, gtk, gdk, glib and my own libs
all in one.

> If so, I've found that the easiest way to debug them is to set
> breakpoints AFTER the module is loaded (i.e., after gdb knows about its
> symbols). For example, if there is a way to harmlessly load the module
> with the gimp, do that. Then interrupt the program and set your
> breakpoint(s) as normal.
> 
> If your module does something naughty before you can do this, you'll
> need to find out what function in Gimp loads the module and set a break
> there. After the module is loaded, its symbol table will be available to
> you.
> 
> The problem is that gdb doesn't know that modules even exist. If that
> wasn't bad enough, if you attempt to add symbols from the modules (via
> add-symbol-file), you'll need to know the starting address for the text
> of the the module (after it is loaded into memory, that is)! Yikes!
> 

Yikes is right. Someone on the gimp newsgroups suggested something
similar so I'll be trying it this week (provided I can get more than 10
minutes of work done). If it doesn't work, looks like I'll be going the
static compile route. Ugh!

Thanks for the suggestions.

L