linux-kernel - Re: [PATCH] [condingstyle] Add chapter on tests

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Message-ID: <4659978D.6020802@s5r6.in-berlin.de>
Date:	Sun, 27 May 2007 16:37:01 +0200
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
CC:	Auke Kok <auke-jan.h.kok@...el.com>, randy.dunlap@...cle.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Scott Preece <sepreece@...il.com>
Subject: Re: [PATCH] [condingstyle] Add chapter on tests

Jan Engelhardt wrote:
> +	if (is_prime(number) == true)
> +		return 0;
> +	if (is_prime(number) == false)
> +		return 1;
> +
> +should be:
> +
> +	if (is_prime(number))
> +		return 0;
> +	if (!is_prime(number))
> +		return 1;
> +
> +As far as pointers or functions returning an integer are concerned,
> +using long form tests helps to distinguish between pointers and bools
> +or functions returning boolean or integer, respectively.
> +Examples are:
> +
> +	if (p == NULL)
> +		return 1;
> +	if (!p)
> +		return 0;
> +
> +	if (strcmp(haystack, needle) == 0)
> +		return 1;
> +	if (!strcmp(haystack, needle))
> +		return 0;

The latter two examples seem odd.  Didn't you mean the following?

	if (p == NULL)
		return 1;
	if (p)
		return 0;

	if (strcmp(haystack, needle) == 0)
		return 1;
	if (strcmp(haystack, needle))
		return 0;

Perhaps better:

	if (p == NULL)
		return NO_MEMORY;
	if (p)
		return MEMORY;

	if (strcmp(haystack, needle) == 0)
		return IS_SAME;
	if (strcmp(haystack, needle))
		return IS_DIFFERENT;

However, to follow your argument about non-boolean expressions, the
following would be more consequently going into your direction:

	if (p == NULL)
		return NO_MEMORY;
	if (p != NULL)
		return MEMORY;

	if (strcmp(haystack, needle) == 0)
		return IS_SAME;
	if (strcmp(haystack, needle) != 0)
		return IS_DIFFERENT;

I.e., why do the explicit comparison with 0 or NULL only when it is
tested for equality, but not when testing for inequality?

However, I agree with Scott Preece that these rules should be left out
of CodingStyle because they are contentious.

(Disclosure:  I am personally used to "if (p)" and "if (!p)" tests of
pointers and many integer expressions, but I tend to the longer form in
less obvious cases like "if (strcmp(a, b) != 0)".)
-- 
Stefan Richter
-=====-=-=== -=-= ==-==
http://arcgraph.de/sr/
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