Tantalizing gcj Java compiler

[Per Bothner]

> Looks like gcj generates nice assembler code for all our Java class
> files, but unfortunately I can't find any info on the meta data formats
> generated by the compiler for classes, methods, etc.  I know this
> is a work in progress, but I really want to know more about the gcj metadata
> so I can begin work on our embedded support for this compiler.  Is there
> any more info (header files, texinfo docs, etc.) about the metadata emitted
> by the compiler and the run-time support required to initialize the classes?

There will be header files that will be part of libjava.  They will be
released with libjava.  There are various reasons we have to wait,
but we're working as hard as we can.

I don't think we want to document the formats beyond the header files.
At least for a while, we consider these internal interfaces, that are
in a state of flux.

> I really want to know more about the gcj metadata
> so I can begin work on our embedded support for this compiler.

Well, the compiled code is designed specifically to work with our
run-time library, and not any other.  The compiler could in theory
be modified to target another run-time environment, but at this
point that would add more complication than it is worth.  (Of course,
it is free software, so you're free to do it on your own.)  Or you
could modify some other Java environment to match jc1 output, but
that too is a fair bit of work, especially since the data formats
won't be stable immediately.

If you want to puzzle out the formats, look for the macros PUSH_FIELD
(which declares the various fields), and PUSH_FIELD_VALUE (which
initializes a field to the correct value).  But I emphasize again:
These structures *will* change, and probably fairly soon.

Still, we are very interested in working with other groups,
but we are mainly interested in partners with either cash or
who can provide useful and non-legally-encumbered technlogy ...

	--Per Bothner
Cygnus Solutions     bothner@cygnus.com     http://www.cygnus.com/~bothner