Re: [gentoo-dev] compiling java vs. binary

[Bruno Dufour]

On Wed, Mar 17, 2004 at 05:42:17PM -0800, Robin H. Johnson wrote:
> On Wed, Mar 17, 2004 at 07:27:41PM -0600, Joseph Booker wrote:
> > Im wondering if java programs in portage really require to be compiled, I
> > dont no of any that i use (mainly just the jdk and jedit) that has USE
> > flags or anything like that that changes the files compiled, so whats the
> > point of having them compiled when the binary versions would be just the
> > same on any arch?
> In theory the output SHOULD be the same, but in practice this is not
> always true, esp. when you tell javac to compile with optimizations or
> debugging. Also, you have to contend with the non-standard javac options
> (try javac -X with various different javac, esp. across multiple
> platforms).

Well, AFAIK, javac always uses optimization. The -O option is still
there for compatibility reasons, but it does not do anything.  This has
been the case for quite a while. I agree with your point though. There
are many features that can be tweaked when using a java compiler (the
jikes compiler is even more configurable than javac). Some compilers
(like javac from Sun's J2DK) are not even available on all platforms.
Even if you don't want to tweak the output, different compilers generate
different class files, and have different optimization strategies.  Some
picky tools/jvms also have incompatibilities with the classes that are
generated from certain compilers.

Compiling from source therefore gives you quite a lot of freedom.

--
Bruno Dufour
Sable Research Group
McGill University, Montréal, Canada
http://www.sable.mcgill.ca/~bdufou1/

>
> --
> Robin Hugh Johnson
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