Re: Segmentation fault in gtk2-perl-application

[muppet <scott asofyet org>]

On Mar 30, 2005, at 4:59 PM, Stephan Brunner wrote:

> Of course, I do much more trust the libraries than I trust my own code,

Good -- you understand the principle of "select() is not broken".  :-)

> but I'm only used to *dying* perl scripts (with file, line no. and 
> error message); I never encountered a *segfault* with any perl 
> script!?

Usually this happens as a result of getting the underlying code into an 
odd state.


> I would be very glad if you could help me out with this issue by 
> giving advice on where and how to start investigating what's going 
> (wr)on(g) in my application. Of course, I am happy to provide you any 
> information needed;

What versions of gtk+, glib, Gtk2, and Glib are you using?  what 
OS/dist?

Beyond that, seeing the code is really going to be necessary.


> not knowing what information might help, I only attached the output of 
> gdb for a "bt" command.

the backtrace was very useful, in that it points out that error is 
occurring deep inside gtk+, in a function that should not really have 
any cause to generate a segfault.  this usually means there is memory 
corruption somewhere.

If you're on an x86 system, please try running your program with 
valgrind.  Don't be surprised by "still reachable" leaks (glib has lots 
of memory that it assumes lives for the life of the program and 
therefore doesn't clean up) and some "jump on uninitialized value" 
errors from within Xlib; watch for errors that occur when you trigger 
your callback.  If you find something, generate and capture the output 
with --num-callers=50 --- gtk+ applications' stacks tend to be very 
deep, and the defaults only show 5 stack frames.


> (gdb) bt
> #0  0x40769d9c in gtk_path_bar_get_type () from 
> /usr/lib/libgtk-x11-2.0.so.0
> #1  0x402d6ddc in g_main_context_wakeup () from 
> /usr/lib/libglib-2.0.so.0

this is really curious; why would a get_type() function be called 
directly from g_main_context_wakeup()?  this reeks of stack corruption, 
or at the very least heap corruption (getting the wrong pointer in an 
event source).


--
"Ghostbusters" is the best movie of this decade.
  -- Neal, circa 1996, referring to a movie released in 1984.