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Date: Sun, 9 Sep 2007 10:51:20 -0700
From: Luigi Rizzo <rizzo@icir.org>
To: "M. Warner Losh" <imp@bsdimp.com>
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References: <20070906111028.A83649@xorpc.icir.org>
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	from imp@bsdimp.com on Sun, Sep 09, 2007 at 11:18:45AM -0600
Cc: current@freebsd.org
Subject: Re: how to tell 64 vs 32 bit architecture ?
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On Sun, Sep 09, 2007 at 11:18:45AM -0600, M. Warner Losh wrote:
> In message: <20070906111028.A83649@xorpc.icir.org>
>             Luigi Rizzo <rizzo@icir.org> writes:
> : 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).
> 
> It is portable.  gcc, and other compilers, define this when using
> longs and pointers as 64 bit.  There's also ILP32 and ILP64
> programming models, but only windows 64 uses the latter.
> 
> Typically, however, there are better ways to solve problems relating
> to these differences.  What kinds of problems are you trying to solve?

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

If there is no better way i can do this

static __unused char __invalid_pointer[] = "This is an invalid pointer";

#define MY_MAGIC	((void *)__invalid_pointer)

and be done with it.

	cheers
	luigi