Re: core while attached

[Daniel Jacobowitz <drow@mvista.com>]

On Mon, Jan 27, 2003 at 01:32:52PM -0500, Bennett F. Dill wrote:
> I hope that someone out there has the patience to look at my problem :-)
> 
> Hi, I'm working with gdb and I have the -g option on my application.
> Typically I get very descriptive error messages.  This latest problem
> however is really interesting though...  It seems to be a problem with
> libc.so.1...
> 
> [history]
> Anyway, the application runs in the background and is a server to about
> 25 clients concurrently.  It takes a few hours for the app to sigsegv.
> Now, it never dumped a core for some reason, so i just attach gdb to the
> process and continue and wait for the error to rear its head.  Now,
> since the app serves ~25 people, I don't really have time to look around
> with the debugger...  (I'm new to gdb, noo suprise I'm sure)
> [/history]
> 
> So my question is, is it possible to have the gdb that is attached to a
> running process that has hit a signal sigsegv, to dump a core?  This
> way I can leisurly mull over the data.

You're in luck.  Grab a recent version of GDB and use the
"generate-core-file" command.

> More questions I have (totally n00bishness I'm sure), is how can I
> find out what line of code in my app, called the 'deadly' function in
> libc.so.1 (fprintf) and is there any way to view the call to fprintf
> based on the memory address?
> 
> Below is what I get from a where or a BT etc...  If I try to use a
> 'return' I go no where real fast.
> 
> TIA for your assistance :-)
> Ben
> 
> 
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0xff30ceb8 in _getorientation () from /usr/lib/libc.so.1
> (gdb) where
> #0  0xff30ceb8 in _getorientation () from /usr/lib/libc.so.1
> #1  0xff30d0dc in _set_orientation_byte () from /usr/lib/libc.so.1
> #2  0xff300710 in fprintf () from /usr/lib/libc.so.1
> #3  0x3aa80 in ?? ()
> #4  0x30420 in ?? ()
> #5  0x2f6f0 in ?? ()
> #6  0x2c7c8 in ?? ()
> #7  0x2c258 in ?? ()
> (gdb) 

That really looks like you're missing debug info; I don't know if those
are legitimate code addresses on your platform or not.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer