Re: getpid after vfork broken in recent glibc

[Andrew Cagney <cagney at gnu dot org>]

> Hello,
>
> in fork_inferior (fork-child.c), gdb uses vfork () to spawn a child
> process, and then calls getpid () (within gdb_setpgid) from within
> that child process, before doing the execve ().
>
> With current glibc CVS builds, this doesn't work any more, since
> glibc caches the PID in thread-local memory, and memory is shared
> between vfork parent and child.  (In fact, what happens is that
> all subsequent getpid calls in gdb return the pid of the initial
> child that was spawned ...)  This causes various breakage.
>
> Now, according to this libc-hacker thread:
> http://sources.redhat.com/ml/libc-hacker/2004-03/msg00014.html
> gdb's behaviour is actually not standards-compliant, as it is not
> permitted to call getpid () between the vfork and the exec.
>
> Can this be fixed in gdb?

We might as well simply always use fork -- the "performance" benefit is 
hardly valid any more (Hmm, perhaps something related to this is why 
vfork never worked, and hence was disabled, on HP/UX).

Andrew