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From: Jens Gustedt <jens.gustedt@inria.fr>
To: musl@lists.openwall.com
Subject: Re: Explicit casts in ctype.h suppress compiler warnings
Date: Fri, 17 Apr 2015 22:34:17 +0200	[thread overview]
Message-ID: <1429302857.14591.1.camel@inria.fr> (raw)
In-Reply-To: <20150417183511.GJ2875@port70.net>

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Am Freitag, den 17.04.2015, 20:35 +0200 schrieb Szabolcs Nagy:
> #define isdigit(a) (((0?1U:(a))-'0') < 10)
> 
> which works when the conversion rank of a is <= unsigned

but not if it has conversion rank larger then unsigned and the result
of the substraction has a negative result. So what you think of

#define isdigit(a) (((0?1ULL:(a))-'0') < 10ULL)

This ensures that the type of the left is always ullong, so the
substraction overflows to something big if a is not a digit.

Jens


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  parent reply	other threads:[~2015-04-17 20:34 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-17 10:59 Alexander Monakov
2015-04-17 16:49 ` Jens Gustedt
2015-04-17 16:52   ` Rich Felker
2015-04-17 18:24     ` Alexander Monakov
2015-04-17 18:35       ` Szabolcs Nagy
2015-04-17 19:43         ` Szabolcs Nagy
2015-04-17 20:21           ` Rich Felker
2015-04-17 20:32             ` Szabolcs Nagy
2015-04-17 20:34         ` Jens Gustedt [this message]
2015-04-17 21:36       ` Rich Felker
2015-04-18  2:03         ` Morten Welinder
2015-04-17 19:33     ` William Ahern
2015-04-17 16:50 ` Rich Felker

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