Linus Torvalds wrote:
>
> On Fri, 1 Dec 2006, 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.
>>
>> The code snippet
>>
>> | u64 x = PS3_VENDOR_ID_SONY;
>> | printk("PS3_VENDOR_ID_SONY = %lu\n", x);
>>
>> does print the expected (i.e. non-zero) result.
>>
>> Hence this looks like a bug in sparse.
>
> It's really a bug in gcc, but it's documented, so it's a "feature".
>
> Gcc allows large enums, but does so in such a strange manner that it's
> totally hopeless to catch problems. Also, putting a value that is larger
> than "unsigned int" into an enum is really setting yourself up for bugs
> and not even guaranteed to work for standard C, so sparse takes a dim view
> of it and just says that enums are limited in size to "int" or "unsigned
> int".
>
> You can either ignore that warning or just use a #define.
One of the gcc maintainers (Andrew Pinski) told me to set it up that
way, so I figured it was safe.
-Geoff
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