cast truncates bits from constant value (8000000000000000 becomes 0)

[Geert Uytterhoeven]

On Fri, 1 Dec 2006, Al Viro wrote:
> On Fri, Dec 01, 2006 at 03:25:08PM +0100, Geert Uytterhoeven wrote:
> > On Tue, 21 Nov 2006, Geoff Levand wrote:
> > > +enum ps3_vendor_id {
> > > +	PS3_VENDOR_ID_NONE = 0,
> > > +	PS3_VENDOR_ID_SONY = 0x8000000000000000UL,
> > > +};
> > 
> > I've just ran `make C=1' (PPC in 64-bit mode, and sparse is called with -m64),
> > and noticed that sparse (cloned from
> > git://git.kernel.org/pub/scm/devel/sparse/sparse.git a few minutes ago)
> > complains about the second value with:
> > 
> > | warning: cast truncates bits from constant value (8000000000000000 becomes 0)
> > 
> > Section 6.7.2.2.4 of C99 says:
> > 
> > | Each enumerated type shall be compatible with char, a signed integer type, or
> > | an unsigned integer type. The choice of type is implementation-defined, but
> > | shall be capable of representing the values of all the members of the
> > | enumeration.
> 
> FWIW, that code is *not* valid C99; note that all enumeration members must
> fit the range of int (see 6.7.2.2.2).  What you quote speaks about the

You're right. I missed that one.

> IOW, you are using a gccism in an area where gcc is bloody inconsistent
> in the set of bugs it shows in different versions.

Hmmm...

> Generally safe way is to split the anonymous huge enum members into
> single-element enums and pray that gcc will at least stay consistent
> in handling of those.

Or fall back to #defines, which is what we were trying to avoid in the first
place (i.e. group related values together in enums)...

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- Sony Network and Software Technology Center Europe (NSCE)
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