Date: Fri, 7 Sep 2007 09:54:35 -0400 From: Yan <rottled@gmail.com> To: "Luigi Rizzo" <rizzo@icir.org> Cc: current@freebsd.org Subject: Re: how to tell 64 vs 32 bit architecture ? Message-ID: <54b90fdf0709070654h103316f3sa3d423f4ff75fee3@mail.gmail.com> In-Reply-To: <20070907050310.A94579@xorpc.icir.org> References: <20070906111028.A83649@xorpc.icir.org> <20070906222647.GB2737@kobe.laptop> <20070907000950.A91211@xorpc.icir.org> <20070907115021.GA2718@kobe.laptop> <20070907050310.A94579@xorpc.icir.org>
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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@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@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@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 > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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