linux-kernel - Re: [PATCH] time: Fix constant size in kernel/timeconst.h

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Message-Id: <1202596152.22512.34.camel@localhost>
Date:	Sat, 09 Feb 2008 23:29:11 +0100
From:	Johann Felix Soden <johfel@....de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] time: Fix constant size in kernel/timeconst.h

H. Peter Anvin wrote:
> Johann Felix Soden wrote:
> > kernel/timeconst.pl generates only long sized constants in timeconst.pl
> > which gives this warning:
> > 
> > kernel/time.c: In function 'msecs_to_jiffies':
> > kernel/time.c:472: warning: integer constant is too large for 'long' type
> > 
> > unsigned long long is needed.
> Hm, you've just taken a warning and elevated it to a bug.
> 
> According to the C standard, a constant has the shortest type (>= int) 
> needed to hold the constant, and the warning above is somewhat bogus in 
> that context (what version of gcc is that, anyway?)
> 
> ULL is only appropriate to 32-bit machines, or there will be other 
> issues downstream.  The Right Way[TM] to do this would be to get Linux 
> to have the [U]INTxx_C() macros from C99.
> 
> 	-hpa

Sorry for this. Thanks for teaching about the C standard.
About your question: gcc 4.2.3 gave me this warning.
And I'm a little bit surprised because the kernel code is full of
constants with ULL. Is kernel/time.c a special case?

J. F. Soden

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