Matthew, hello. On 2011 Oct 29, at 17:43, Matthew Flatt wrote:
> At Sat, 29 Oct 2011 16:19:53 +0200, Niklas Larsson wrote: >> 2011/10/29 Thomas Chust <ch...@web.de>: >>> 2011/10/29 Norman Gray <nor...@astro.gla.ac.uk>: >>>> [...] >>>> Is there a recommended way to detect whether racket is a 32- or >>>> 64-bit executable? >>>> [...] >>> (require (only-in ffi/unsafe compiler-sizeof)) >>> >>> (compiler-sizeof 'long) ; => 8 on a 64-bit system >>> ; => 4 on a 32-bit system >> That doesn't work in all cases, sizeof(long) is 4 on 64-bit Windows. > Right -- use `_pointer' or `_intptr', and that's probably the strategy > I'd use. The following works: (require (only-in ffi/unsafe ctype-sizeof _pointer)) (ctype-sizeof _pointer) This is also more direct, since I suppose the question I'm actually asking, in asking 32/64, is "what size are the corresponding C pointers?" >> ;; 64bit? : -> boolean >> (define (64bit?) (eq? (expt 2 61) (expt 2 61))) > > This is not a good approach. If you happen to compile on a 64-bit > machine, the compiler will end up constant-folding to > > (define (64bit?) #t) In fact, what I was doing was something like % racket -e '(if (eq? (expt 2 61) (expt 2 61)) "yes" "no")' I'd guess that this isn't vulnerable to the same problem, but the ctype-sizeof method is surely preferable nonetheless. Thanks for this. All the best, Norman -- Norman Gray : http://nxg.me.uk SUPA School of Physics and Astronomy, University of Glasgow, UK _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
