Re: Questions Regarding Null and Casting

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BigChuck19 wrote:

> To check if malloc() returns NULL or not,
> why couldn't one write " if (grades == NULL) ".

One could; there's absolutely nothing wrong with it.

> Say I create a character array called array.
> After initializing all its entries, I then want
> to clear the entire array by making
> each entry hold the null character.  I
> could write something like the following to accomplish this:
> 
> for(i = 0; i < MAXTENTRIES; i++)
>     array[i] = '\0';
> 
> Does the following loop perform the identical operation?
> 
> for(i = 0; i < MAXENTRIES; i++)
>    array[i] = (char) NULL;

No.

> I am confused about the definition of NULL and the use of NULL;

It is best to use NULL in a pointer context
regardless of how any particular implementation defines NULL.

NULL expands to an implementation-defined null pointer constant.

An integral constant expression with the value 0, or such an
expression cast to type void * , is called a null pointer constant.

An integral constant expression shall have integral type and shall
only have operands that are integer constants, enumeration constants,
character constants, sizeof expressions, and floating constants that
are the immediate operands of casts.  Cast operators in an integral
constant expression shall only convert arithmetic types to integral
types, except as part of an operand to the sizeof operator.

-- 
pete

Thread

Questions Regarding Null and Casting BigChuck19 <bc19@mailinator.com> - 2011-06-03 21:52 +0000
  Re: Questions Regarding Null and Casting Ian Collins <ian-news@hotmail.com> - 2011-06-04 10:13 +1200
    Re: Questions Regarding Null and Casting Ian Collins <ian-news@hotmail.com> - 2011-06-04 10:16 +1200
  Re: Questions Regarding Null and Casting Keith Thompson <kst-u@mib.org> - 2011-06-03 15:25 -0700
    Re: Questions Regarding Null and Casting Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-03 20:45 -0700
  Re: Questions Regarding Null and Casting pete <pfiland@mindspring.com> - 2011-06-03 18:38 -0400
  Re: Questions Regarding Null and Casting Angel <angel+news@spamcop.net> - 2011-06-03 23:23 +0000
    Re: Questions Regarding Null and Casting Keith Thompson <kst-u@mib.org> - 2011-06-03 17:24 -0700
  Re: Questions Regarding Null and Casting "J. J. Farrell" <jjf@bcs.org.uk> - 2011-06-04 00:45 +0100
  Re: Questions Regarding Null and Casting Keith Thompson <kst-u@mib.org> - 2011-06-03 17:27 -0700
  Re: Questions Regarding Null and Casting pete <pfiland@mindspring.com> - 2011-06-03 21:12 -0400
  Re: Questions Regarding Null and Casting Shao Miller <sha0.miller@gmail.com> - 2011-06-06 20:11 -0500

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