Debugging GDB and breaking?

Debugging GDB and breaking?

[James Sampson]

Hello

I'm debugging the GDB with the GDB - Not to catch a bug, but to investigate 
what's going on. In that case I wan't to step through everything the GDB does 
when just working with it manualy. Where I am now, I've loaded a file into the 
GDB being debugged, and I want the other GDB to take over, so I can see what 
happens, when the GDB actually sets a breakpoint in this small testprogram. 
But when I type e.g. "break main", the control never goes back to the other 
GDB, so I can't see what's going on.
Isn't there a command to issue a breakpoint at the next line of code instead 
of a obsolute position (name, address)?

Or could someone tell me where to look in the source code for the functions 
which places a breakpoint?.

Best Regards
James
						

Re: Debugging GDB and breaking?

[Michael Elizabeth Chastain]

Some general hints for debugging gdb:

I start with "gdb /my/gdb/to/debug/bin/gdb".  I like to use a stable gdb
for the top gdb, such as the vendor-supplied gdb or gdb 5.3.  Also this
helps separate, in my mind, the top gdb from the inferior gdb.

Then I immediately:

  (gdb) set prompt [top] 
  [top] break help_command
  [top] set args /program/under/test

The first line distinguishes the top gdb from the inferior gdb.

The second line lets me get back to the top gdb from the inferior gdb.
If the inferior gdb is waiting at a prompt, I just type "help foo"
and take the breakpoint at help_command.

The third line is the normal way to provide arguments to the inferior gdb.

After that, in your specific case, you want to break at break_command
and then use "next" and "step" from there.

Hope this helps,

Michael C

Re: Debugging GDB and breaking?

[Andreas Schwab]

Michael Elizabeth Chastain <mec@shout.net> writes:

|> Some general hints for debugging gdb:
|> 
|> I start with "gdb /my/gdb/to/debug/bin/gdb".  I like to use a stable gdb
|> for the top gdb, such as the vendor-supplied gdb or gdb 5.3.  Also this
|> helps separate, in my mind, the top gdb from the inferior gdb.
|> 
|> Then I immediately:
|> 
|>   (gdb) set prompt [top] 
|>   [top] break help_command
|>   [top] set args /program/under/test
|> 
|> The first line distinguishes the top gdb from the inferior gdb.

If you start gdb from the build directory you get these thing
automatically through the .gdbinit file in this directory.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Deutschherrnstr. 15-19, D-90429 Nürnberg
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: Debugging GDB and breaking?

[Grant Edwards]

On Wed, Dec 18, 2002 at 09:23:30AM -0600, Michael Elizabeth Chastain wrote:

> Some general hints for debugging gdb:
> 
> I start with "gdb /my/gdb/to/debug/bin/gdb".  I like to use a stable gdb
> for the top gdb, such as the vendor-supplied gdb or gdb 5.3.  Also this
> helps separate, in my mind, the top gdb from the inferior gdb.
> 
> Then I immediately:
> 
>   (gdb) set prompt [top] 
>   [top] break help_command
>   [top] set args /program/under/test
> 
> The first line distinguishes the top gdb from the inferior gdb.

Running them in separate ttys prevents confusion for me:

 gdb -tty=<whatever> /my/buggy/gdb

Or I use the equivalent menu item in DDD or Insight...

-- 
Grant Edwards
grante@visi.com

RE: Debugging GDB and breaking?

[James Sampson]

>Some general hints for debugging gdb:

Cool!



>I start with "gdb /my/gdb/to/debug/bin/gdb". I like to use a stable gdb
>for the top gdb, such as the vendor-supplied gdb or gdb 5.3. Also this
>helps separate, in my mind, the top gdb from the inferior gdb.


I didn't even know the 5.3 was out - Gonna grab that immediatly :-)




>After that, in your specific case, you want to break at break_command
>and then use "next" and "step" from there.


Ok, so the "break_command" is the first function to be called when setting a 
breakpoint? :-)



>Hope this helps,


Sure did, thanks :-D

Best Regards
James