Re: how to tell 64 vs 32 bit architecture ?

How about this:

#define MY_MAGIC ((sizeof(intptr_t)==4) ? 0Xdeadbeef : 0xdeadbeefd00de123)

You can also test it via 'if(sizeof(intptr_t)&0x4)'.

This is assuming you won't run this on a 16 bit architecture :p

-yan

On 9/7/07, Luigi Rizzo <rizzo_at_icir.org> wrote:
>
> On Fri, Sep 07, 2007 at 02:50:21PM +0300, Giorgos Keramidas wrote:
> > On 2007-09-07 00:09, Luigi Rizzo <rizzo_at_icir.org> wrote:
> > >On Fri, Sep 07, 2007 at 01:26:47AM +0300, Giorgos Keramidas wrote:
> > >>On 2007-09-06 11:10, Luigi Rizzo <rizzo_at_icir.org> wrote:
> > >>> hi,
> > >>> i was wondering what is the proper way to tell a 64 vs 32 bit
> > >>> architecture.
> > >>>
> > >>> I see that some code in sys/ uses  ' #ifdef __LP64__ ' but i am not
> > >>> sure if this is generic enough (ie not gcc or FreeBSD specific),
> > >>> and also suitable for userland (i.e. works on linux or other
> platforms
> > >>> as well).
> > >>
> > >> This is usually needed to differentiate between a feature "X" which
> > >> behaves differently in amd64 vs. i386 vs. sparc vs. sparc64, etc.
> > >
> > > i am actually looking at pointer sizes, as i need to do some pointer
> > > manipulation going through intptr_t, and need to know that in the
> > > preprocessor because some constants need to be 32 or 64 bit depending
> > > on that, and are not trivial (i.e. not 0, 1 or something i can build
> > > with size-agnostic expressions)
> >
> > An intptr_t can safely hold any void pointer value, and C99 says:
> >
> > %     7.18.1.4 Integer types capable of holding object pointers
> > %
> > % 1   The following type designates a signed integer type with the
> > %     property that any valid pointer to void can be converted to
> > %     this type, then converted back to pointer to void, and the
> > %     result will compare equal to the original pointer:
> > %
> > %         intptr_t
> >
> > What sort of manipulation?  Can this sort of manipulation be written in
> > a way that uses sizeof(intptr_t) instead of 4, 8, or preprocessor magic?
>
> i need to do this:
>
> #ifdef BUILT_FOR_64BIT_POINTERS
> #define MY_MAGIC        0xdeadbeefd00de123      /* 64 bit */
> #else
> #define MY_MAGIC        0xdeadbeef              /* 32 bit */
>
> If you know of a way to implement this without preprocessor
> magic, i am all ears. If the values were simpler (eg all ones or so)
> i could have used ~((unitptr_t)0) but this is not the case here
>
> cheers
> luigi
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