Re: process attaching gdb to itself

Michael Elizabeth Chastain
2003-09-28T22:25:12Z

Hello,

char cmd [256];
sprintf (cmd, "gdb attach %d", getpid ());
system (cmd);

'system' waits for the program that it calls to finish.
Thus, your program is waiting for gdb to finish before it
does anything.

Try the appended program which uses raw fork/exec.
It works for me on red hat linux 8, native i686-pc-linux-gnu.

If you try to do this in production code then you are likely
to run into a blizzard of race conditions, error cases,
and signal handling problems. If you are doing this as a learning
experience, that's great -- read up on 'man fork' and
'man execlp', and check out a book on Linux systems programming.

Michael C
GDB QA Guy

===

#include <stdio.h>

int main ()
{
int pid = fork ();
if (pid == -1)
{
/* error */
fprintf (stderr, "fork error\n");
exit (2);
}

if (pid != 0)
{
/* parent process */
char spid [256];
sprintf (spid, "%d", pid);
execlp ("gdb", "gdb", "a.out", spid, NULL);
/* execlp returns only if error */
fprintf (stderr, "execlp error\n");
_exit (2);
}

/* child process */
sleep (5);
printf ("hello hacker\n");
return 0;
}