> pid = fork();
> if (pid == 0)
> { 3 lines of code }
> while (waitpid(pid, &status, 0) != pid);
>
> Er wait, I *can* see how it can go wrong. If fork() fails ...
Don't forget EINTR, either.
I don't know how Exim deals with SIGCHLD, but from the Linux manual:
POSIX.1-2001 specifies that if the disposition of SIGCHLD is set to
SIG_IGN or the SA_NOCLDWAIT flag is set for SIGCHLD (see sigaction(2)),
then children that terminate do not become zombies and a call to wait()
or waitpid() will block until all children have terminated, and then
fail with errno set to ECHILD. (The original POSIX standard left the
behaviour of setting SIGCHLD to SIG_IGN unspecified.) Linux 2.6 con-
forms to this specification. However, Linux 2.4 (and earlier) does
not: if a wait() or waitpid() call is made while SIGCHLD is being
ignored, the call behaves just as though SIGCHLD were not being
ingored, that is, the call blocks until the next child terminates and
then returns the process ID and status of that child.
I can check a bunch other systems RSN, but to be safe, I suggest to just
deal with waitpid() returning -1, ignoring the condition for anything
but EINTR.
Michael
