Re: Working On Classpath

[Andrew John Hughes]

On Thu, 2004-05-27 at 16:45, Thomas Zander wrote:
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> On Thursday 27 May 2004 12:17, Andrew John Hughes wrote:
> > > since I still can't apt-get it, its not on my radar.  (I'm wondering
> > > how many distro's ship kaffe.)
> >
> > Kaffe is in Debian stable and unstable
> Hmm, I use testing..
> 
So do I -- but I imagine you still have the stable package lists... ;-)
I imagine the unstable version will eventually make its way into
testing, anyway.
> >  So, Ant simulates make's functionality, but there
> > is nothing to simulate detecting the JVM as the autotools can do (or, if
> > there is, you don't see it in any current uses of Ant).
> ant is a shell-script; it does its best to look for java. It uses JAVACMD, 
> or JAVA_HOME if it can't find a java in the path.
> I'm not sure this answers your concerns though, and still expects a fully 
> implemented JVM.
> 
My bad here -- I should have said its the Java compiler that's the
problem.  Running ant tries to use Sun's compiler from tools.jar by
default -- I don't think there's any detection here (and there is a
javac (mapped to jikes) in the path).

> > If [the autotools] are flexible enough to
> > also work with Java code (which they probably predate), this is an
> > advantage of their design.
> 
> That is something they can't do; they can call jikes from the command line; 
> but that is a LOT slower then ant with jikes, or ant with javac. This is 
> because a) ant knows which 'clusters' of files have changed and passes 
> them all to the compiler in one compile-run, and  b) ant can do dependency 
> checking (which file needs a recompile because it depends on a changed 
> one) by reading the class files.
> 
Which is where Ant excels as a Java-optimised build tool -- Makefiles
have no concept of what class files are, and so can't pull out the
required dependencies.  I'm not sure how Ant runs with other compilers
like Jikes, but with Sun's, it calls classes from tools.jar rather than
the binary -- this probably gives a speed increase.  Of course, the
dependency handling doesn't always seem to work -- I have a habit of
doing a clean of my classes files before a build, because otherwise old
class files tend to hang around and hide errors in the code (with Jikes,
anyway).
> 
> - -- 
> Thomas
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Cheers,
-- 
Andrew :-)
 
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