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From: scjones@sdrc.UUCP (Larry Jones)
Newsgroups: comp.lang.c
Subject: Re: absolute variable positioning
Keywords: hardware constraints
Message-ID: <793@sdrc.UUCP>
Date: 8 Sep 89 21:38:47 GMT
References: <471@sagpd1.UUCP>
Organization: Structural Dynamics Research Corp., Cincinnati
Lines: 31

In article <471@sagpd1.UUCP>, jharkins@sagpd1.UUCP (Jim Harkins) writes:
> Due to some hardware considerations I have a special block of memory that I
> have to use for storage of some variables.  Lets say it starts at address FOO.
> In C, whats the best way to say "integer fred in normal mem, struct wilma
> somewhere after FOO, struct barney somewhere after FOO, struct bam_bam in
> normal mem", etc?  The best I can come up with is
> 
> pointer = FOO
> struct a *wilma = pointer
> pointer += sizeof(struct a)
> struct b *barney = pointer
> pointer += sizeof(struct b) * NUMBER_OF_BARNEYS     /* array of barneys */

I would suggest packaging all of the variables you want to be in
the special memory into a single struct and then declaring a
pointer to that struct that is initialized appropriately.

	struct special {
	   struct a wilma;
	   struct b barney;
	   } *p = (struct special *)FOO;

That solves the problem for static allocation, if you ever need
dynamic allocation then you still have to write a malloc.
----
Larry Jones                         UUCP: uunet!sdrc!scjones
SDRC                                      scjones@SDRC.UU.NET
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-Calvin