Subject: Re: Platform device matching, & weird strncmp usage
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: "Kurtis D. Rader" <kdrader@us.ibm.com>
Cc: Linux Kernel list <linux-kernel@vger.kernel.org>
In-Reply-To: <20060107192458.GA12409@us.ibm.com>
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	 <20060107192458.GA12409@us.ibm.com>
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Date: Sun, 08 Jan 2006 09:14:59 +1100
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> I can't speak to the correctness of that code but your understanding of
> strncmp() is incorrect. From "GNU C Library Application Fundamentals":
> 
>     This function is the [sic] similar to strcmp, except that no more
>     than size wide characters are compared. In other words, if the two
>     strings are the same in their first size wide characters, the return
>     value is zero.
> 
> And this has been may experience for the past 20 years and is confirmed by
> this trivial program which prints zero in both cases:
> 
> #include <string.h>
> #include <stdio.h>
> int main() {
>     printf("%d\n", strncmp("abc","abcd",3));
>     printf("%d\n", strncmp("abcd","abc",3));
> }

Except that in my example, the count was larger than both strings...

Anyway, it happens to not be a problem as the string I was comparing was
not in fact different.

Ben.


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