Re: proced: ppid of process ID 0 can be 0

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Roland.Winkler@physik.uni-erlangen.de,  lekktu@gmail.com,  emacs-devel@gnu.org
> Date: Tue, 30 Dec 2008 12:11:15 -0500
> 
> >> AFAIK we're talking about ppid, and this info is always present, so if
> >> it's absent, don't return the process.
> 
> > Can you find any authoritative reference that says we can rely on
> > this?  I couldn't even find a decent documentation of /proc when I was
> > working on these primitives, let alone some information about what
> > attributes are always present or how that changes with the kernel
> > version.
> 
> The ppid is in the /proc/NNN/stat file, those attributes are
> distinguished by their order, so if it's missing the ordering gets
> messed up, so it can't be missing.  As for the /proc/NNN/stat file
> missing, that would mean that pretty much all the attributes returned by
> `ps' would be missing, so we can definitely count on its presence.

Sorry, this doesn't even come close to being an "authoritative
reference".  These are just deliberations based on some concept of how
/proc is implemented in the Linux kernel, and I have no idea how close
is this concept to the truth.