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On 5/31/2011 2:09 PM, Andreas Leitgeb wrote:
> Lawrence D'Oliveiro<ldo@geek-central.gen.new_zealand>  wrote:
>> In message<is30d8$5fl$1@dont-email.me>, Joshua Cranmer wrote:
>>> Besides, all autoconf gets you is setting up the hundreds of #defines.
>>> It does nothing else with respect to the #ifdef mess.
>> Still better than anything Java can offer.
>
> This is now about Java versus C, isn't it?
> Java has one big advantage: The compiled thing is typically still
> "portable". For this, it would "need" to do any OS-#ifdef'ery at
> runtime, anyway, not at compile-time.
>

note:
it could be done at JIT-time, which is not strictly the same as 
run-time, since JIT-time operations need not involve runtime checks...

however, yes, 'javac' in such a case would likely spit out code with 
every possible ifdef branch included, and then the classloader/JIT would 
discard any of the branches which are irrelevant to the given target.


how this would "best" be done in a standard JVM is uncertain, but my VM 
(technically, not a JVM) basically handles it via block-folding and 
attributes (ifdef blocks are folded off into their own 
functions/methods, which are invisibly called by the parent method, with 
any dropped blocks having no-op calls).


or such...