Re: Fix "warning: cast from pointer to integer of different size"

[Dmitry Timoshkov]

"Erik de Castro Lopo"  wrote:
> /* get pointer to object containing list element */
> #define LIST_ENTRY(elem, type, field) \
> - ((type *)((char *)(elem) - (unsigned int)(&((type *)0)->field)))
> - ((type *)((char *)(elem) - (unsigned long)(&((type *)0)->field)))

It should be replaced with FIELD_OFFSET instead.

Fix "warning: cast from pointer to integer of different size"

[Erik de Castro Lopo]

Dmitry Timoshkov wrote:
> "Erik de Castro Lopo"  wrote:
> > /* get pointer to object containing list element */
> > #define LIST_ENTRY(elem, type, field) \
> > - ((type *)((char *)(elem) - (unsigned int)(&((type *)0)->field)))
> > - ((type *)((char *)(elem) - (unsigned long)(&((type *)0)->field)))
>
> It should be replaced with FIELD_OFFSET instead.

FIELD_OFFSET is defined in include/winnt.h.

Now I could include winnt.h into include/wine/list.h but that doesn't
seem right. I could also copy it,but having two difinitions of the
same macro is also not right. I'm also sure that moving the definition
from include/winnt.h to include/wine/list.h will break existing code.

Any suggestions for dealing with this?

Cheers,
Erik

Fix "warning: cast from pointer to integer of different size"

[Dmitry Timoshkov]

"Erik de Castro Lopo"  wrote:
> > > /* get pointer to object containing list element */
> > > #define LIST_ENTRY(elem, type, field) \
> > > - ((type *)((char *)(elem) - (unsigned int)(&((type *)0)->field)))
> > > - ((type *)((char *)(elem) - (unsigned long)(&((type *)0)->field)))
> >
> > It should be replaced with FIELD_OFFSET instead.
>
> FIELD_OFFSET is defined in include/winnt.h.
>
> Now I could include winnt.h into include/wine/list.h but that doesn't
> seem right. I could also copy it,but having two difinitions of the
> same macro is also not right. I'm also sure that moving the definition
> from include/winnt.h to include/wine/list.h will break existing code.
>
> Any suggestions for dealing with this?

Replacing (unsigned int) cast by (unsigned long) doesn't guarantee
anything, long can be a 32-bit entity on a 64-bit platform.

Fix "warning: cast from pointer to integer of different size"

[Erik de Castro Lopo]

Dmitry Timoshkov wrote:
> "Erik de Castro Lopo"  wrote:
> > FIELD_OFFSET is defined in include/winnt.h.
> >
> > Now I could include winnt.h into include/wine/list.h but that doesn't
> > seem right. I could also copy it,but having two definitions of the
> > same macro is also not right. I'm also sure that moving the definition
> > from include/winnt.h to include/wine/list.h will break existing code.
> >
> > Any suggestions for dealing with this?
>
> Replacing (unsigned int) cast by (unsigned long) doesn't guarantee
> anything, long can be a 32-bit entity on a 64-bit platform.

I'm perfectly happy to accept that, but the real question was,
"what is the best way to get FIELD_OFFSET in include/wine/list.h?".

I see four options:

0) Include include/winnt.h into include/wine/list.h. Ugly!

1) Copy definition of FIELD_OFFSET macro from include/winnt.h to
    include/wine/list.h. Ugly!

2) Move the definition of FIELD_OFFSET macro from include/winnt.h to
    include/wine/list.h. This will probably break existing code. Ugly!

3) Add a definition if FIELD_OFFSET wrapped in #ifndef. This is the
    least ugly option but would cause surprising results if one or
    the other was changed.

So, to rephrase the question, which of the above would actually be
accepted as a patch? If none of them are good enough (highly 
likely) can someone please suggest an alternative that would be
acceptable?

Cheers,
Erik

Fix "warning: cast from pointer to integer of different size"

[Juan Lang]

> - Add a definition if FIELD_OFFSET wrapped in #ifndef. This is the
> least ugly option but would cause surprising results if one or
> the other was changed.

Personally, I think this looks the best.  As far as which is likely to
get accepted.. often you have to try first to find that out ;-)
--Juan

Fix "warning: cast from pointer to integer of different size"

[David Laight]

On Tue, Apr 22, 2008 at 11:50:05PM +0900, Dmitry Timoshkov wrote:
> "Erik de Castro Lopo"  wrote:
> > /* get pointer to object containing list element */
> > #define LIST_ENTRY(elem, type, field) \
> > - ((type *)((char *)(elem) - (unsigned int)(&((type *)0)->field)))
> > - ((type *)((char *)(elem) - (unsigned long)(&((type *)0)->field)))

How about:
    ((type *)((char *)(elem) - ((char *)(&((type *)0)->field) - (char *)0)))

David

Fix "warning: cast from pointer to integer of different size"

[Erik de Castro Lopo]

David Laight wrote:
> On Tue, Apr 22, 2008 at 11:50:05PM +0900, Dmitry Timoshkov wrote:
> > "Erik de Castro Lopo"  wrote:
> > > /* get pointer to object containing list element */
> > > #define LIST_ENTRY(elem, type, field) \
> > > - ((type *)((char *)(elem) - (unsigned int)(&((type *)0)->field)))
> > > - ((type *)((char *)(elem) - (unsigned long)(&((type *)0)->field)))
>
> How about:
>     ((type *)((char *)(elem) - ((char *)(&((type *)0)->field) - (char *)0)))

Much, much better, thank you. I don't know why I didn't see it myself.

Cheers,
Erik