On Fri, Jan 18, 2008 at 08:41:22AM -0800, Linus Torvalds wrote:
> 
> 
> On Fri, 18 Jan 2008, [EMAIL PROTECTED] wrote:
> >   */
> > +#ifdef __HAVE_ARCH_PTE_SPECIAL
> > +# define HAVE_PTE_SPECIAL 1
> > +#else
> > +# define HAVE_PTE_SPECIAL 0
> > +#endif
> >  struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long 
> > addr, pte_t pte)
> >  {
> > -   unsigned long pfn = pte_pfn(pte);
> > +   unsigned long pfn;
> > +
> > +   if (HAVE_PTE_SPECIAL) {
> 
> I really don't think this is *any* different from "#ifdefs in code".

One fundamental difference is that with the above syntax we always
compile both versions of the code - so we do not end up with one
version that builds and another version that dont.

This has always striked me as a good reason to do the above and
I think it is busybox that does so with success.

        Sam
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