Re: [Linux-NTFS-Dev] Portability of NTFS userspace code

[Anton A. <ai...@ca...>]

On Mon, 2 Dec 2002, Anton Altaparmakov wrote:
> On 2 Dec 2002, Richard Russon wrote:
> > We also seem to be relying on the size of __packed__ enums.  It's a
> > nice feature, but it's another gcc extension.  In our code we can:
> 
> I _don't_ care. I don't want pragmas everywhere! gcc doesn't understand
> pragmas anyway so the only way to be compatible with MSVC would be to do
> some disgusting things like:
> 
> #ifdef MSVC
> #define __PACKED__ <insert correct pragma crap here>
> #define __UNPACKED__ <insert correct pragme crap here>
> #define __attrbiute__ <what do we put here so it disappears?!?>
> #define __packed__ <what do we put here so it disappears?!?>
> #else
> #define __PACKED__ <what do we put here so it disappears?!?>
> #define __UNPACKED__ <what do we put here so it disappears?!?>
> #endif
> 
> And then we rewrite:
> 
> >   typedef enum {
> >     ABC = 4,
> >   } RICH __attribute__ ((__packed__));
> 
> to:
> 
> __PACKED__
> typedef enum {
> 	ABC = 4,
> } RICH __attriute__ ((packed__));
> __UNPACKED__

Having thought about this some more, it is not that bad. But we should
take it a bit further to make it cleaner.

Let's have a PACKED_TYPEDEF define as well as a PACKED_TYPEDEF_END (or
something to that effect, feel free to use a better name...).

So the header files would then become:


PACKED_TYPEDEF enum {
	blah = 4,
} myenumname PACKED_TYPEDEF_END;

or 

PACKED_TYPEDEF struct {
	blah = 4,
} mystructname PACKED_TYPEDEF_END;

And then have the compat.h header file (or whatever the name was) deal
with defining PACKED_TYPEDEF{,_END} depending on compiler/OS or whatever
you like. That makes it even nicer than the __attribute__ strangeness and
the pragma strangeness that gcc and msvc have respectively.

So basically feel free and do something along those lines if you wish...

Cheers,

	Anton
-- 
Anton Altaparmakov <aia21 at cantab.net> (replace at with @)
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/