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Re: Lisp object that refers to a C struct

From: Paul Eggert
Subject: Re: Lisp object that refers to a C struct
Date: Thu, 18 Oct 2012 09:42:14 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121009 Thunderbird/16.0 
On 10/18/2012 04:09 AM, Eli Zaretskii wrote:
>> but in general it's not safe to convert a pointer to
>> > an Emacs fixnum, as this can lose information: the payload
>> > of an Emacs fixnum is typically narrower than a pointer.
> A pointer that is properly aligned has no problem with this.

It can have problems on hosts where USE_LSB_TAG is 0,
because the conversion to Emacs fixnum can lose high-order
bits in the pointer.
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