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From: mouse@mcgill-vision.UUCP
Newsgroups: comp.sys.ibm.pc,comp.lang.c
Subject: Re: Segment & offset of pointers in MS C v4.0
Message-ID: <703@mcgill-vision.UUCP>
Date: Mon, 23-Mar-87 18:56:13 EST
Article-I.D.: mcgill-v.703
Posted: Mon Mar 23 18:56:13 1987
Date-Received: Fri, 27-Mar-87 05:42:00 EST
References: <247@creed.tcom.stc.co.uk>
Organization: McGill University, Montreal
Lines: 22
Keywords: C pointers
Xref: utgpu comp.sys.ibm.pc:2550 comp.lang.c:1330

In article <247@creed.tcom.stc.co.uk>, arden@creed.tcom.stc.co.uk (Bruce Arden) writes:
> #define P_SEG(p)    (unsigned)((long)( (char far *)(p) ) >> 16)
> #define P_OFF(p)    (unsigned)((long)( (char far *)(p) ))

> This appeared to give the correct result (although it did generate
> some redundant code) with data pointers.  However it gave register DS
> as the segment of a near code pointer.

I don't know the particular compiler, but I'm not surprised.  After
all, you *are* casting it to a data pointer!  Try something like

#define CODEP_SEG(p)    (unsigned)((long)( (int (far *)())(p) ) >> 16)
#define CODEP_OFF(p)    (unsigned)((long)( (int (far *)())(p) ))

for code pointers.

					der Mouse

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