Am 09.10.2009, 03:38 Uhr, schrieb Stephen Hocking
<stephen.hock...@gmail.com>:
It appears as if the documentation does not match up with the reality
in Linux's case. That's what the empirical evidence suggests anyway.
The code does does a waitpid after receiving the SIGCHLD to determine
what child process has exited and then searches its list of sessions
looking for that particular pid, so as to tidy up.
My reception is: if the process wants SIGCHLD, it will have to install its
own handler, because the default disposition for this signal is SIG_IGN (=
discard signal and do not turn child process into a zombie).
So use your patch for FreeBSD, feed it to the upstream maintainer with a
copy of this thread and relevant quotes from the standard and manpage and
move on. :)
The alternative is to do away with SIGCHLD and use waitpid((pid_t)-1,
WNOHANG) to poll for children that have exited.
I can to some degree understand that implementation of sigwait, as if
you state your intention to wait for a particular signal, that means
that you don't wish to ignore it.
That's outside the standard. If it works on a particular Linux kernel
version that doesn't mean it will work on every other. Why lose yourself
in empirical programming if there are standards?
--
Matthias Andree
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