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Re: Lisp object that refers to a C struct

From: Eli Zaretskii
Subject: Re: Lisp object that refers to a C struct
Date: Thu, 18 Oct 2012 06:50:49 +0200

> Date: Wed, 17 Oct 2012 15:08:52 -0700
> From: Paul Eggert <address@hidden>
> CC: address@hidden
> On 10/17/2012 01:46 PM, Eli Zaretskii wrote:
> >> How do you convert the integer into the C struct pointer?
> >   struct foo *pwatch = (struct foo *)XLI (watch_descriptor);
> > 
> > where watch_descriptor is a Lisp integer.
> Won't this have problems on platforms where
> or where MOST_POSITIVE_FIXNUM < (EMACS_INT) pwatch?

Given what XLI does, I don't see how this could happen, with
watch_descriptor being a Lisp integer.

> Also, suppose someone makes up a random integer
> and then passes it as the watch descriptor --
> wouldn't Emacs dump core?

No, because, like Stephen  says, the descriptor is first validated
against a list of known ones.

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