Re: [PATCH 8/10] Re: [2.6-BK-URL] NTFS: 2.1.19 sparse annotation, cleanups and a bugfix

[Anton Altaparmakov <aia21@cam.ac.uk>]

On Sat, 25 Sep 2004, Linus Torvalds wrote:
> I personally believe that people use enum's largely in two (independent) 
> ways:
> 
>  - a convenient compile-time constant:
> 
> 	enum {
> 		DevEnableMask = 1UL << 0,
> 		DevIRQMask = 1UL << 5,
> 		DevError = 1UL << 31
> 	};
> 
>    where you never actually _save_ an enum anywhere. In this case, the 
>    typing is very convenient indeed.
> 
>  - a "type enumerator":
> 
> 	enum token_type {
> 		TOKEN_IDENT = 1,
> 		TOKEN_NUMBER,
> 		TOKEN_MACRO,
> 	...
> 
>    where the enum actually is used as a variable to distinguish different 
>    cases. In this case, the per-enum typing ends up being possibly even 
>    confusing, since using a constant will have a potentially _different_ 
>    type than loading that constant from a variable.
> 
> The second case is why I think it's a sane thing to warn if anybody ever 
> creates a variable (or structure/union member) with an enum that used the 
> typing features. Not because we can't make the enum fit all the values, 
> but because the types simply WILL NOT MATCH. They fundamentally cannot, 
> since we took the approach of having per-entry types.
> 
> And for sparse, since the type is _the_ most important part of anything, 
> we should warn when the types won't match.

What does sparse do at the moment when the enum size has been changed 
away from sizeof(int) using __attribute__ ((__packed__))?

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/