converting a jar into a shared lib - requirements ?

Hi All,

While it works fine most of the tine, I have trouble converting some
jar files into shared lib where I get errors like:

$ gcj -O0 -g0 -shared java-getopt-1.0.13.jar -o libgetopt-1.0.13.so
gnu/getopt/LongOpt.java: In class 'gnu.getopt.LongOpt':
gnu/getopt/LongOpt.java: In constructor
'(java.lang.String,int,java.lang.StringBuffer,int)':
gnu/getopt/LongOpt.java:103: internal compiler error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.
For Debian GNU/Linux specific bug reporting instructions,
see <URL:file:///usr/share/doc/gcc-4.2/README.Bugs>.

What are the requirements for a jar to be "convertible" into shared
lib ? I must be missing something trivial there !....

Cheers
David