Date: Sun, 9 Sep 2007 10:51:20 -0700 From: Luigi Rizzo <rizzo@icir.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: current@freebsd.org Subject: Re: how to tell 64 vs 32 bit architecture ? Message-ID: <20070909105120.B34897@xorpc.icir.org> In-Reply-To: <20070909.111845.-861032475.imp@bsdimp.com>; from imp@bsdimp.com on Sun, Sep 09, 2007 at 11:18:45AM -0600 References: <20070906111028.A83649@xorpc.icir.org> <20070909.111845.-861032475.imp@bsdimp.com>
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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
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