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From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: More NULL questions
Message-ID: <11229@smoke.BRL.MIL>
Date: 6 Oct 89 19:02:30 GMT
References: <5950001@hpldola.HP.COM>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 22

In article <5950001@hpldola.HP.COM> jg@hpldola.HP.COM (Joe Gilray) writes:
>1) what is the danger with using
>         if (ptr != NULL) ...
>   as apposed to
>         if (ptr != (struct thing *)NULL) ...

There is no danger, assuming the C implementation is correct.

>2) Is there danger using
>         my_func(a, NULL, b);
>   as apposed to
>         my_func(a, (struct thing *)NULL, b);
>   when
>   a) you are using function prototypes?

The only danger is that someone may port your code to a "classic C"
environment and miss making the necessary edit.

>   b) you are NOT using function prototypes (like me)?

Yes, it is erroneous to feed NULL to a function where a pointer argument
is expected.