Converting a JAR into a gcj-statically-linked SO

Thu Jan 10 08:14:00 GMT 2008

On Jan 9, 2008 4:30 PM, Andrew Haley <aph@redhat.com> wrote:
> Matthijs van de Water writes:
> > OK, that sounds easy but I'm not really sure how to do it... I'm
> > looking at the Makefile in libjava and the output of doing a "make
> > libgcj.la", which looks like it should contain the information I need.
> > But frankly I'm not really sure which of the huge amount of .o files
> > should be AR-ed together in the .a file.
> >
> > Can I somehow edit the libjava/Makefile to convince libtool to do the
> > dirty job for me?
>> At the thought of anything to do with libtool I begin to panic. :-)
>> You don't have to do anything like that. For every file that is
> compiled by libtool, two objects are created: one called foo.o and one
> called ./libs/foo.o. The non-PIC one is foo.o.
>> So, to get an archive with just the PIC libs it's
>> find . -name .libs | while read i; do ls -1 $i/*.o ; done | xargs ar q foo.a
>> Pretty hacky but good enough for an experiment.

Thanks a bunch, that was the info I needed. After some fiddling* I've
managed to create a libgcj.a with all the PIC .o files in it.
This version links fine with the JAR.o file and my little C++ wrapper
API which hides all Java and best of all: it works (on x86)!
The only down-side is that the resulting shared library is 24MB big
even after stripping and optimizing. I was expecting a lot less, is
there any chance the compiler is linking in stuff that is not actually
needed?
Thanks again for your help,
Matthijs
*) For the interested, in the compiled libjava dir run:
mkdir -p tmp/.libs; cd tmp/.libs; for i in ./libltdl/.libs/libltdlc.a
classpath/native/fdlibm/.libs/libfdlibm.a
../libffi/.libs/libffi_convenience.a
../boehm-gc/.libs/libgcjgc_convenience.a ; do ar x ../../$i ; done ;
cd ../.. ; find . -name .libs |while read i ; do ls -1 $i/*.o |grep -v
libgcj_bc.o ; done |xargs ar q mylibgcj.a ; rm -rf tmp