> Why exactly ptrace(PT_TRACE_ME, ...) call after the fork in the debugged app
> is not enough for you?

Because you don't always build the debugged process. For instance, I
need to trace a mach-O binary. Our gdb is not able to launch it yet, the
only way is to attach it once it is launched. If I want to catch it at
process startup, I need such a feature.

-- 
Emmanuel Dreyfus.
"Of course, it runs NetBSD" -- http://www.netbsd.org
manu@netbsd.org