Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ucsd!sdcsvax!ucsdhub!hp-sdd!hplabs!hpda!hpcupt1!hpcuhb!hpcllla!hpcllz2!walter
From: walter@hpcllz2.HP.COM (Walter Murray)
Newsgroups: comp.lang.c
Subject: Re: Help me cast this!
Message-ID: <7330002@hpcllz2.HP.COM>
Date: 4 May 88 16:04:42 GMT
References: <294@fedeva.UUCP>
Organization: HP NSG/ISD Computer Language Lab
Lines: 42

Bill Daniels writes:

> How do I cast the malloc() in the following program to avoid 
> the lint cries of "warning: illegal pointer combination" et al?

[program abbreviated]

> #include <stdio.h>
> main()	
> {
> char *malloc();
> struct outfile {
>         int j;
>         int k;
>       } (*output)[];
> output = malloc(sizeof(struct outfile) * 3);
> }

> THIS IS MY LINT'S OUTPUT:

> trial.c
> ==============
> warning: illegal pointer combination
> (12)  	
> warning: possible pointer alignment problem
> (12)  	

To avoid the "illegal pointer combination", try:

   output = (struct outfile (*)[])malloc(sizeof(struct outfile) * 3);

The "possible pointer alignment problem" warning comes from the
fact that malloc(3) is declared to return char*, even though we
know that the alignment of its return pointer is such that it can
be used for anything.  To get rid of that warning, try:

   output = (struct outfile (*)[])(int)malloc(sizeof(struct outfile) * 3);

Conversions of pointers to integral types and back are implementation-
defined, but this should work if int on your machine is wide enough
to hold a pointer.  If not, try long instead.

		 --Walter Murray