At 22:26 01/09/2001, Jamie Lokier wrote:
>Andries.Brouwer@cwi.nl wrote:
> >[...]
> > However, a union is not so bad. It seems a pity to avoid unions
> > and waste 4 bytes for every inode with separate i_bdev and i_cdev
> > instead of a single i_bcdev.
>
>Please, a union of different pointer types is much nicer. You can have
>i_bdev and i_cdev without wasting any bytes.
>
>This form works with GCC 2.96:
>
> union {
> struct char_device * i_cdev;
> struct block_device * i_bdev;
> };
It sure does. One of the nicest new gcc features IMHO!
>If you're using a really old compiler that doesn't support anonymous unions,
>(GCC 2.95 might be in this category, I'm not sure),
GCC 2.95 does NOT support this. I only found out after I had people
complain to me that Linux-NTFS userspace tools would not compile for them
and it turned out they were using gcc-2.95... and I 2.96. - I have since
then verified this myself:
egcs and gcc up to 2.95 do not support unnamed structs/unions.
gcc-2.96 and gcc-3.0 support them fine.
> then you'll need this:
>
> #define i_bdev __i_bcdev_union.i_bdev
> #define i_cdev __i_bcdev_union.i_cdev
> union {
> struct char_device * i_cdev;
> struct block_device * i_bdev;
> } __i_bcdev_union;
Neat trick! Thanks! I was wondering what to do with NTFS TNG driver (which
uses unnamed structs/unions extensively) and this just might solve my
problems without having to rewrite half the driver... (-;
Best regards,
Anton
-- "Nothing succeeds like success." - Alexandre Dumas -- Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Linux NTFS Maintainer / WWW: http://linux-ntfs.sf.net/ ICQ: 8561279 / WWW: http://www-stu.christs.cam.ac.uk/~aia21/- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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