Re: Self-detection of native code execution (Was Re: [Caml-list] Accuracy of Gc.stat ())

[Richard Jones <rich@annexia.org>]

On Sat, Nov 22, 2003 at 03:20:40PM +0100, Daniel B?nzli wrote:
> 
> Le 22 nov. 03, ? 12:49, Richard Jones a ?crit :
> 
> >>Neat trick. This _ought_ to work, but it doesn't for some reason:
> >>
> >>	let arg = (true, false)
> >>	external is_bytecode : bool * bool -> bool = "%field0" "%field1"
> >>
> >>	let () =
> >>	  if is_bytecode arg then
> >>	    print_endline "Bytecode!"
> >>	  else
> >>	    print_endline "Native!"
> >>
> >>Perhaps someone can explain why ...
> 
> Nice try, too bad it doesn't work. I would even prefer that one :
> 
> let arg = true
> external is_bytecode : bool ->  bool = "%identity" "%boolnot"
> 
> let () =
>   if is_bytecode arg then
>     print_endline "Bytecode!"
>   else
>     print_endline "Native!"
> 
> 
> >OK, closer inspection of the manual[*] reveals why this doesn't work.
> >Surely OCaml should flag the above code as a bug, because there are
> >fewer than the magical 6 arguments?
> 
> The strange thing is that the function given by Kim also have fewer 
> than 6 arguments.

True, but his code doesn't actually use the values of the arguments
passed to the C functions.

What is needed is a primitive function which ignores its arguments and
returns a known value. But I don't think there is such a primitive in
the current compiler. (Not as far as I can see by looking at
bytecomp/translcore.ml anyway).

Rich.

-- 
Richard Jones. http://www.annexia.org/ http://freshmeat.net/users/rwmj
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