Re: gdb 5.2.90-cvs, gcc 3.2-7 and lyx thread problem

[Ben Stanley <bds02@uow.edu.au>]

I have now upgraded my gdb to current cvs. Version string is

GNU gdb 5.2.90_2002-11-22-cvs

The problems I previously reported remain unchanged. I have been
performing tests using gdb directly on RH 8.0.

I also tried running lyx under gdb under gdb. At the point where the
instance of gdb debugging lyx crashes, the state is:

(gdb) info threads
* 1 Thread 8192 (LWP 12396)  [No stack.]

Program received signal SIGSEGV, Segmentation fault.
0x0809e3f6 in get_next_frame (frame=0x0) at blockframe.c:287
287       return frame->next;
(top-gdb) where
#0  0x0809e3f6 in get_next_frame (frame=0x0) at blockframe.c:287
#1  0x080d356d in find_relative_frame (frame=0x0,
level_offset_ptr=0xbfffef6c)
    at stack.c:1608
#2  0x080d4517 in info_threads_command (arg=0x0, from_tty=1) at
thread.c:471
#3  0x0808bfde in do_cfunc (c=0x0, args=0x0, from_tty=1) at
cli/cli-decode.c:53
#4  0x0808d8ea in cmd_func (cmd=0x83b7838, args=0x0, from_tty=1)
    at cli/cli-decode.c:1523
#5  0x0811110e in execute_command (p=0x83a865c "", from_tty=1) at
top.c:711
#6  0x080d5eb9 in command_handler (command=0x83a8650 "info threads")
    at event-top.c:504
#7  0x080d62d8 in command_line_handler (rl=0x860dd38 "info threads")
    at event-top.c:799
<snip>

Examining the value of selected_frame reveals that it is 0x0 when
find_relative_frame is called by info_threads_command.

This is about as far as I can go without learning the internals of gdb
myself. I'd really like to be able to use gdb on lyx. As it stands
currently, gdb is of almost no use.

I noticed that when I start LyX, it gave the message:

(gdb) run
Starting program:
/share/install/linux/extras/lyx/lyx-current-doc/lyx-devel/src/lyx
[New Thread 8192 (LWP 12521)]

but when it hits a breakpoint, I get
[New Cannot find thread 16385: invalid thread handle
(gdb)

How can the thread number change? Of course its invalid - there are not
other new threads created (that gdb reports). What variable can I set a
watchpoint on so that I can find out when the 'current thread' changes?

Ben.

On Wed, 2002-11-20 at 08:39, Ben Stanley wrote:
> Hi,
> 
> I was trying to use gdb on lyx-1.3.0cvs. I would place a breakpoint in
> the lyx code (Counter::reset) and run until the program hit the
> breakpoint. When that happened, gdb went crazy:
> 
> (gdb) run
> [New Thread 8192 (LWP 26110)]
> Unknown token, keepLyXAspectRatio, skipping.
> Unknown token, keepLyXAspectRatio, skipping.
> [New Cannot find thread 16385: invalid thread handle
> 
> This LyX was built with the Qt front end, and I'm told by the LyX
> developers that only a single thread is used.
> 
> I then tried to find out what's going on with the threads:
> 
> (gdb) info threads
> * 1 Thread 8192 (LWP 26128)  [No stack.]
> 
> lyx: SIGHUP signal caught
> 
> Segmentation fault
> 


-- 
Ben Stanley, PhD candidate
School of Information Technology and Computer Science
University of Wollongong