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Date: 12 Mar 88 10:35:04 GMT
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Subject:  Re: Header problems

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From:         Chris Torek <chris@mimsy.uucp>
Subject:      Re: Header problems
Comments: To: info-c@BRL-SMOKE.arpa
To:           Vic Kapella <SXJVK@ALASKA>

[This makes three.]
In article <121@polygen.UUCP> pablo@polygen.uucp (Pablo Halpern) writes:
>For compilers that don't support (void *), you must have
>a compiler-specific definition of NULL:

No.

>    #define NULL 0        /* If sizeof(int) == sizeof(char *) */
> or
>    #define NULL 0L        /* if sizeof(long) == sizeof(char *) */

Either is technically legal.  The former suffices, is not machine
dependent, and is correct.

>Since the above #defines are necessarily machine (and compiler) specific,

The definition of NULL (as 0, or if you have a dpANS-conformant
compiler, as (void *)0) is not machine dependent.  What *is* machine
dependent is whether uncasted 0 in unprototyped function calls appears
to work.  Using uncasted 0L appears to work (but is nonetheless wrong)
on IBM PCs using large model compilers.
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:    chris@mimsy.umd.edu    Path:    uunet!mimsy!chris