Re: [Xen-devel] [PATCH] libfsimage: Make it build on NetBSD

[Bastian Blank <bastian@xxxxxxxxxxxx>]

On Sun, Sep 23, 2007 at 12:48:11PM +0100, Keir Fraser wrote:
> The ISO spec is pretty unambiguous: "The c argument is an int, the value of
> which the application shall ensure is a character representable as an
> unsigned char or equal to the value of the macro EOF. If the argument has
> any other value, the behavior is undefined."

Â7.4

> If we sensibly take 'representable' to mean 'representable with the same
> integer value', then the casts are clearly needed for compliance.

No. 'representable' means that the value fits in unsigned char (0-255 on
common systems). See example 6 of Â5.1.2.3 how the standard uses
representable. A cast would force that, if you use unsigned char.

> And read glibc's ctype.h -- it goes to some effort to support 'signed char'
> input, but makes it clear this is "for broken old programs".

Yeah, it explicitely does the change which the explicite conversion to
unsigned char would do.

> This seems to be one of the ugly corners of the C spec where the truth is
> not very palatable. :-)

Haha. You want some of i + i++?

Bastian

-- 
Virtue is a relative term.
                -- Spock, "Friday's Child", stardate 3499.1

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