Re: find command with gdb v7.0

[Paul Pluzhnikov <ppluzhnikov@google.com>]

On Tue, Oct 27, 2009 at 3:07 AM, James Pandavan
<james.pandavan@googlemail.com> wrote:

> I wanted to try out the new find command wivh gdb v7.0. I used the example
> given in this page
> (http://sourceware.org/gdb/current/onlinedocs/gdb_11.html#SEC91). I just
> added one line (line no 5) to the example given. It looks like the search
> doesn't start at given location.
>
> In the attached output, you can see that the find command says it couldn't
> find the first word or part of it, but is able to find the second word. Is
> it a bug, or am I doing something wrong?
>
> (gdb) find greet,+100,"greetings"
> Pattern not found.
> (gdb) find greet,+100,"ings"
> Pattern not found.

This currently searches for a sequence of bytes 'i', 'n', 'g', 's', '\0'.

There is in fact no such sequence of bytes in your program, which is why
you get "not found" answer. I'll grant you that it is not what one might
reasonably expect, and the manual doesn't explicitly say the terminating
NUL is included in the search pattern.

I think removing the trailing NUL is a better fix; one could always put
it back with

  find greet,+100,"gentleman",'\0'

if one is really interested in the string with terminating NUL, whereas
currently you'd have to spell each byte separately, which is rather
inconvenient:

  (gdb) p greet
  $1 = 0x4005a8 "greetings gentleman"

  (gdb) find greet,+100,'g','r','e','e','t','i','n','g','s'
  0x4005a8
  1 pattern found.

Feel free to open a GDB enhancement request for this.

>
> Thanks,
> James Pandavan
>
> ----------------------------------------------------------------------------------------------------------
>
> GNU gdb (GDB) 7.0-ubuntu
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> For bug reporting instructions, please see:
> <http://www.gnu.org/software/gdb/bugs/>...
> Reading symbols from
> /tmp/gdb/gdb_7.0-0ubuntu1_amd64/data/usr/bin/a.out...done.
> (gdb) break main
> Breakpoint 1 at 0x4005f4: file test.cpp, line 5.
> (gdb) list 3,12
> 3 int main()
> 4 {
> 5 char * greet="greetings gentleman";
> 6 static char hello[] = "hello-hello";
> 7 static struct { char c; short s; int i; }
> 8 __attribute__ ((packed)) mixed
> 9 = { 'c', 0x1234, 0x87654321 };
> 10 printf ("%s\n", hello);
> 11 return(0);
> 12 }
> (gdb) run
>
> Breakpoint 1, main () at test.cpp:5
> 5 char * greet="greetings gentleman";
> (gdb) n
> 10 printf ("%s\n", hello);
> (gdb) p greet
> $1 = 0x4006fc "greetings gentleman"
> (gdb) find greet,+100,"greetings"
> Pattern not found.
> (gdb) find greet,+100,"ings"
> Pattern not found.
> (gdb) find greet,+100,"gentleman"
> 0x400706
> 1 pattern found.
> (gdb)
>
>
>
>
>



-- 
Paul Pluzhnikov