Re: [PATCH v2 06/14] mingw: use real pid

From: Johannes Sixt <j6t@kdbg.org>
Date: Jan 19, 2010, 18:19 UTC
Message-ID: <201001191919.16070.j6t@kdbg.org>
In-Reply-To: <40aa078e1001181433v3c86f147wf3e6aace4501c1a8@mail.gmail.com>

On Montag, 18. Januar 2010, Erik Faye-Lund wrote:

Show 18 quoted lines

> On Sat, Jan 16, 2010 at 10:12 AM, Erik Faye-Lund wrote:
> > On Sat, Jan 16, 2010 at 9:03 AM, Johannes Sixt <j6t@kdbg.org> wrote:
> >> On Freitag, 15. Januar 2010, Erik Faye-Lund wrote:
> >>> No. If I do, the pid becomes invalid after the process is finished,
> >>> and waitpid won't work. I couldn't find anywhere were we actually were
> >>> closing the handle, even after it was finished. So I don't think we
> >>> leak any more than we already did (for non-daemon purposes).
> >>
> >> Previously, this handle was closed by _cwait() (it was the "pid"), so we
> >> didn't leak it.
> >
> > Oh, I see. My planned route with this (before I looked for where the
> > handle was closed), was to maintain some sort of list of each started
> > PID and their handle, and lookup in that list instead of using
> > OpenProcess. I guess that would solve the problem here, but it feels a
> > bit nasty. Not as nasty as introducing a leak, though.
>
> What I had in mind was something along these lines:

Given that that the process ID is the user-visible (and system-wide unique) identifier of a process, this looks like the only reasonable way to go. Your implementation looks good as well.

> +	/* store process handle */

	/*
	 * The process ID is the human-readable identifier of the process
	 * that we want to present in log and error messages. The handle
	 * is not useful for this purpose. But we cannot close it, either,
	 * because it is not possible to turn a process ID into a process
	 * handle after the process terminated.
	 * Keep the handle in a list for waitpid.
	 */

Show 6 quoted lines

> +	num_pinfo++;
> +	pinfo = xrealloc(pinfo, sizeof(struct pid_info) * num_pinfo);
> +	pinfo[num_pinfo - 1].pid = pi.dwProcessId;
> +	pinfo[num_pinfo - 1].proc = pi.hProcess;
> +
>  	return (pid_t)pi.dwProcessId;

-- Hannes