Re: process attaching gdb to itself

[Andrew Cagney <ac131313@redhat.com>]

> 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