Re: process attaching gdb to itself

Andrew Cagney
2003-09-28T22:35:35Z

> 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.

Is the kernel Linux? JeffJ and I just discovered that:

$ sleep 1000
^Z
PID 1234 suspended
$ gdb sleep 1234
...
(gdb)

works on BSD but fails on GNU/Linux. When doing an attach, BSD always
generates something for wait4 to consume. GNU/Linux does not, leaving
GDB stuck in wait4 :-(

Andrew