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Re: [Bug-gnulib] addition: wait-process.h, wait-process.c, 2nd round

From: Paul Eggert
Subject: Re: [Bug-gnulib] addition: wait-process.h, wait-process.c, 2nd round
Date: 27 Oct 2003 00:31:47 -0800
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3

Bruno Haible <address@hidden> writes:

> I think this scenario is
>   - extremely rare, due to the time it requires until a PID is reused,
>   - due to an inherent limitation of waitpid in POSIX: there is no way to
>     ask waitpid: "Tell me when the process terminates but keep the process
>     in zombie state afterwards."

If you can assume the XSI standard extension to POSIX, it sounds like
there is a way to solve the problem: you can pass WNOWAIT to waitpid.
WNOWAIT keeps the process whose status is returned in a waitable
state. The process may be waited for again with identical results, and
this sounds like it's what you want.  See

So you could use WNOWAIT if available, and fall back on the current
code if it's not available.

> > I'm a bit dubious about the semantics, portability, and
> > understandability of structs whose members are volatile.
> It's the same as with const:

Yes, but the same objections apply to const.  Anyway, your other
arguments were good ones, though I admit that I still have a few
qualms, as it's unlikely that compiler bugs in this area will be found
and fixed.

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