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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: A glitch regarding the usual malloc() idiom
Date: Wed, 20 Jul 2016 16:55:24 -0700
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Malcolm McLean <malcolm.mclean5@btinternet.com> writes:
> On Wednesday, July 20, 2016 at 8:30:01 PM UTC+1, Keith Thompson wrote:
>> 
>> I don't *care* that I'm asking for 160 bytes.  Or if I do, I can
>> compute it easily enough.  I care, in this case, that I'm allocating
>> space for 40 objects of the type magptr points to.  (I'd probably use
>> some symbolic name rather than the constant 40, but that's not a big
>> deal for this example.)
>>
> Sometimes it matters, most often it doesn't. 
> But even if there is no serious constraint on memory usage, it
> helps to be able to see something concrete. It's likely we know 
> that a float will by 4 bytes, so sizeof(float) is meaningful, it
> can mentally be replaced by "four".  

If you need to see something concrete, you can add a comment:

    magptr = malloc(40 * sizeof *magptr); /* 160 bytes */

Keeping the comment in sync with the code is left as an exercise.

[...]

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"