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From: arnold@ucsfcgl.UUCP (Ken Arnold%CGL)
Newsgroups: net.lang.c
Subject: Re: void *
Message-ID: <9831@ucsfcgl.UUCP>
Date: Thu, 24-Apr-86 14:36:56 EST
Article-I.D.: ucsfcgl.9831
Posted: Thu Apr 24 14:36:56 1986
Date-Received: Sat, 26-Apr-86 06:16:38 EST
References: <1883@ucsfcgl.UUCP> <728@bentley.UUCP>
Reply-To: arnold@ucsfcgl.UUCP (Ken Arnold)
Organization: UCSF Computer Graphics Lab
Lines: 35

In article <728@bentley.UUCP> kwh@bentley.UUCP (KW Heuer) writes:
>In article <1883@ucsfcgl.UUCP> ucsfcgl!arnold (Ken Arnold%CGL) writes:
>>Purists will note that I really should say
>>	ptr = (some_type *) malloc(10 * sizeof *ptr);
>>But eventually malloc() will be of type "void *".
>
>Okay, enlighten me.  When I first saw the idea of "void *" I thought it was
>to be a name for the most restrictive pointer type ("ALIGN *" for those who
>know the malloc source).  Then when I rechecked, I found that it was a new
>name for the least restrictive pointer type, "char *".  Now you seem to say
>that the cast operator is unnecessary in your example.  I'd like some more
>detail about this beast.  Specifically, suppose we have the following:
>	void  *v;
>	char  *c;
>	short *h;
>	ALIGN *a;
>Of the 12 nontrivial assignment statements, which ones will ANSI C accept
>without a cast?  What will lint accept (with/without cast)?

Well, as *I* understand it (and my draft is, of course, out of date),
(void *) can be cast to any other pointer type without complaint.
So

	ptr = malloc( ... );

would be as legal as

	int_var = float_var;

i.e., the conversion would be automatic and silent (because it is
guaranteed to work properly).  Presumably, any other pointer assignment
would generate a warning unless accompained by a cast (and I sure hope
it is silent if I explicitly cast it).

		Ken Arnold