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From: Dr Nick <3-nospam@temporary-address.org.uk>
Newsgroups: comp.lang.c
Subject: Re: int vs. unsigned int vs. size_t
Date: Sun, 01 May 2011 14:16:34 +0100
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Steve Keller <keller@no.invalid> writes:

> This is a style question.  To iterate through an array I often use
> code similar to the following:
>
> 	#define ASIZE(a) (sizeof(a) / sizeof((a)[0])
> 	int a[] = { ... };
>
> 	void foo(void)
> 	{
> 		int i;
> 		for (i = 0; i < ASIZE(a); i++)
> 			/* do something with a[i]. */
> 	}
>
> With all warnings enabled, gcc will warn about a comparison between
> signed and unsigned integer types, because sizeof() yields a size_t
> which is unsigned.  To eliminate that warning I could use unsigned int
> or size_t for the variable i.  But IMO int feels most natural and
> size_t might have unwanted overhead, if it is a large integer type and
> I know that the array size will be very small (i.e. less than INT_MAX
> elements).
>
> So, what type for i do you prefer in cases like this?

I hit another issue with this a couple of days ago.  If you /do/ use an
unsigned type for 'i', and the array has no items in it, and you use GCC
with -W you get:
warning: comparison is always false due to limited range of data type

With a cast of the result of the sizeof division, and a normal signed
int, you get no warnings. 

I have to confess that this confuses me.
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