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Re: Questions Regarding Null and Casting

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Keith Thompson <kst-u@mib.org> writes:

> BigChuck19 <bc19@mailinator.com> writes:
>[snip]
>
>> My question concerns the use of the cast (int *).  The book states
>> that one must write " if (grades == (int *) NULL) " because if there
>> is insufficient memory available, malloc() returns NULL, which is then
>> cast into a pointer to an integer by the (int *) preceding the call to
>> malloc().
>
> The cast is an explicit conversion.  It's unnecessary because the value
> of NULL will be implicitly converted to the type of grades (int*) before
> it's compared.  [snip]

Just an amusing note here.  6.5.9p4 says:

    Otherwise, at least one operand is a pointer.  If one
    operand is a pointer and the other is a null pointer
    constant, the null pointer constant is converted to the type
    of the pointer.  If one operand is a pointer to an object or
    incomplete type and the other is a pointer to a qualified or
    unqualified version of void, the former is converted to the
    type of the latter.

If NULL is defined as '(void*)0', then both of the last two
sentences apply, and each operand is converted to the type
of the other.

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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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