Re: Trouble with gdb 6.6 and one particular app on FreeBSD 7.0...

["Kip Macy" <kip dot macy at gmail dot com>]

On 9/29/07, Eric Schuele <e.schuele@computer.org> wrote:
> Hello,
>
> I have a particular app that I am unable to debug using gdb.  When I
> attach to the app and continue it, gdb begins to take up 100% of my cpu.
>  It will do this forever (well longer than I've ever waited).
>
> I am able to debug this particular app on my 6.2-STABLE machine.  And I
> can debug other apps on my 7.0 machine.  I've tried both gdb 6.1 and gdb
> 6.6 on my 7.0 machine with no change in behavior.
>
> I first thought maybe I had done something odd when rebuilding my
> kernel/world?  But I've built a second 7.0 machine and stuck with the
> GENERIC kernel and I have the same results.
>
> Most times I can not break into the app once I have continued it.  I
> have attached gdb to gdb to watch what it is doing and it appears to
> give me a few different backtraces, though it is always one of maybe
> three traces.  [See below for bt of gdb attached to gdb, unfortunately
> its not the same bt I was seeing... but may offer some insight?]
>
> Has anyone seen behavior like this?  What else can I provide that might
> help diagnose this?

This sounds more like a ptrace bug / change in behavior. My first
guess is that the behavior of ptrace has changed and that gdb is
expecting a different return code from the one that it is getting. Is
your app threaded? The default threading library has changed. Can you
produce a small test case that causes this behavior?

Thanks.

 -Kip



>
> --
> Regards,
> Eric
>
> Several backtraces of gdb ==> gdb in same session...
>
> Program received signal SIGINT, Interrupt.
> 0x0805241b in find_pc_sect_section (pc=681465567, section=0x0)
>     at objfiles.c:762
> 762     in objfiles.c
> (gdb) bt
> #0  0x0805241b in find_pc_sect_section (pc=681465567, section=0x0)
>     at objfiles.c:762
> #1  0x0805249a in find_pc_section (pc=681465567) at objfiles.c:776
> #2  0x080aa087 in find_pc_partial_function (pc=681465567, name=0xbfbfe590,
>     address=0xbfbfe588, endaddr=0xbfbfe58c) at blockframe.c:189
> #3  0x080eed68 in handle_inferior_event (ecs=0xbfbfe574) at infrun.c:1776
> #4  0x080ed63e in wait_for_inferior () at infrun.c:1009
> #5  0x080ed46a in proceed (addr=4294967295, siggnal=TARGET_SIGNAL_DEFAULT,
>     step=0) at infrun.c:827
> #6  0x080ea249 in continue_command (proc_count_exp=0x0, from_tty=1)
>     at infcmd.c:642
> #7  0x0808082b in do_cfunc (c=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:62
> #8  0x08082e6d in cmd_func (cmd=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:1666
> #9  0x08054cbd in execute_command (p=0x2890c081 "", from_tty=1) at top.c:455
> #10 0x080feadf in command_handler (command=0x2890c080 "c") at
> event-top.c:519
> #11 0x080ff307 in command_line_handler (rl=0x2895b112 "c") at
> event-top.c:804
> #12 0x28319826 in rl_callback_read_char () from /lib/libreadline.so.7
> #13 0x080fe1cf in rl_callback_read_char_wrapper (client_data=0x0)
>     at event-top.c:179
> #14 0x080fe96f in stdin_event_handler (error=0, client_data=0x0)
>     at event-top.c:432
> ---Type <return> to continue, or q <return> to quit---
> #15 0x080fd860 in handle_file_event (event_file_desc=0) at event-loop.c:730
> #16 0x080fd090 in process_event () at event-loop.c:343
> #17 0x080fd0d9 in gdb_do_one_event (data=0x0) at event-loop.c:380
> #18 0x080fa46c in catch_errors (func=0x80fd0a5 <gdb_do_one_event>,
>     func_args=0x0, errstring=0x8262c9e "", mask=6) at exceptions.c:515
> #19 0x0809b11b in tui_command_loop (data=0x0) at
> .././gdb/tui/tui-interp.c:151
> #20 0x080fa95d in current_interp_command_loop () at interps.c:278
> #21 0x0804eec7 in captured_command_loop (data=0x0) at .././gdb/main.c:101
> #22 0x080fa46c in catch_errors (func=0x804eebc <captured_command_loop>,
>     func_args=0x0, errstring=0x824f0e6 "", mask=6) at exceptions.c:515
> #23 0x0804fd3c in captured_main (data=0xbfbfead4) at .././gdb/main.c:826
> #24 0x080fa46c in catch_errors (func=0x804eefd <captured_main>,
>     func_args=0xbfbfead4, errstring=0x824f0e6 "", mask=6) at
> exceptions.c:515
> #25 0x0804fdad in gdb_main (args=0xbfbfead4) at .././gdb/main.c:835
> #26 0x0804eeb1 in main (argc=3, argv=0xbfbfeb28) at gdb.c:44
> (gdb) c
> Continuing.
> ^C
> Program received signal SIGINT, Interrupt.
> 0x080b80e1 in set_register_cached (regnum=15, state=0) at regcache.c:434
> 434     regcache.c: No such file or directory.
>         in regcache.c
> (gdb) bt
> #0  0x080b80e1 in set_register_cached (regnum=15, state=0) at regcache.c:434
> #1  0x080b8186 in registers_changed () at regcache.c:472
> #2  0x080f063c in prepare_to_wait (ecs=0xbfbfe574) at infrun.c:2917
> #3  0x080f05f8 in keep_going (ecs=0xbfbfe574) at infrun.c:2895
> #4  0x080ef284 in handle_inferior_event (ecs=0xbfbfe574) at infrun.c:2021
> #5  0x080ed63e in wait_for_inferior () at infrun.c:1009
> #6  0x080ed46a in proceed (addr=4294967295, siggnal=TARGET_SIGNAL_DEFAULT,
>     step=0) at infrun.c:827
> #7  0x080ea249 in continue_command (proc_count_exp=0x0, from_tty=1)
>     at infcmd.c:642
> #8  0x0808082b in do_cfunc (c=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:62
> #9  0x08082e6d in cmd_func (cmd=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:1666
> #10 0x08054cbd in execute_command (p=0x2890c081 "", from_tty=1) at top.c:455
> #11 0x080feadf in command_handler (command=0x2890c080 "c") at
> event-top.c:519
> #12 0x080ff307 in command_line_handler (rl=0x2895b112 "c") at
> event-top.c:804
> #13 0x28319826 in rl_callback_read_char () from /lib/libreadline.so.7
> #14 0x080fe1cf in rl_callback_read_char_wrapper (client_data=0x0)
>     at event-top.c:179
> #15 0x080fe96f in stdin_event_handler (error=0, client_data=0x0)
>     at event-top.c:432
> #16 0x080fd860 in handle_file_event (event_file_desc=0) at event-loop.c:730
> ---Type <return> to continue, or q <return> to quit---q
> Quit
> (gdb) c
> Continuing.
> ^C
> Program received signal SIGINT, Interrupt.
> 0x28784c0b in ?? () from /lib/libc.so.7
> (gdb) bt
> #0  0x28784c0b in ?? () from /lib/libc.so.7
> #1  0xbfbfe2b0 in ?? ()
> #2  0x28980c20 in ?? ()
> #3  0x00000004 in ?? ()
> #4  0x00003f80 in ?? ()
> #5  0x00000000 in ?? ()
> (gdb) c
> Continuing.
> ^C
> Program received signal SIGINT, Interrupt.
> 0x2874cbbb in ptrace () from /lib/libc.so.7
> (gdb) bt
> #0  0x2874cbbb in ptrace () from /lib/libc.so.7
> #1  0x08068b42 in i386fbsd_resume (ptid={pid = -1, lwp = 0, tid = 0},
> step=0,
>     signal=TARGET_SIGNAL_CHLD) at i386fbsd-nat.c:76
> #2  0x080ed0de in resume (step=0, sig=TARGET_SIGNAL_CHLD) at infrun.c:626
> #3  0x080f05ed in keep_going (ecs=0xbfbfe574) at infrun.c:2892
> #4  0x080ef284 in handle_inferior_event (ecs=0xbfbfe574) at infrun.c:2021
> #5  0x080ed63e in wait_for_inferior () at infrun.c:1009
> #6  0x080ed46a in proceed (addr=4294967295, siggnal=TARGET_SIGNAL_DEFAULT,
>     step=0) at infrun.c:827
> #7  0x080ea249 in continue_command (proc_count_exp=0x0, from_tty=1)
>     at infcmd.c:642
> #8  0x0808082b in do_cfunc (c=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:62
> #9  0x08082e6d in cmd_func (cmd=0x28977190, args=0x0, from_tty=1)
>     at .././gdb/cli/cli-decode.c:1666
> #10 0x08054cbd in execute_command (p=0x2890c081 "", from_tty=1) at top.c:455
> #11 0x080feadf in command_handler (command=0x2890c080 "c") at
> event-top.c:519
> #12 0x080ff307 in command_line_handler (rl=0x2895b112 "c") at
> event-top.c:804
> #13 0x28319826 in rl_callback_read_char () from /lib/libreadline.so.7
> #14 0x080fe1cf in rl_callback_read_char_wrapper (client_data=0x0)
>     at event-top.c:179
> #15 0x080fe96f in stdin_event_handler (error=0, client_data=0x0)
>     at event-top.c:432
> ---Type <return> to continue, or q <return> to quit---
>
>
>
>