phc-discussions - Re: [PHC] Specification of a modular crypt format (2)

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Message-ID: <5617B542.2010506@openwall.com>
Date: Fri, 09 Oct 2015 15:38:26 +0300
From: Alexander Cherepanov <ch3root@...nwall.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Specification of a modular crypt format (2)

On 2015-10-09 15:18, Thomas Pornin wrote:
>>> 		acc = (acc << 6) + (unsigned)d;
>>
>> ...but this one seems entirely redundant:-)
>
> This cast is for readability. Readability depends on who is doing the
> reading, and, in this case, the cast is for me. I tend to add explicit
> casts when switching between signed and unsigned integer types, because
> long ago I ran into trouble with signedness issues(*) and I got into the
> habit of making things more obvious.
>
> The cast is redundant because the C compiler already applies it -- so
> the compiler won't mind.
>
>
> (*) This code:
>
> 	unsigned x = 10;
> 	long y = -1;
> 	if (x < y) {
> 		...
> 	}
>
> will execute the code in the 'if' on a 32-bit machine, not on a 64-bit
> machine(**); and this is not undefined behaviour. In both cases, the
> result is clearly and unambiguously defined by the standard.

Sure. But in this case, there is no switching of signedness, both 
operands have "unsigned" type. Sorry, I don't see what an additional 
cast could achieve.

-- 
Alexander Cherepanov