http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6319 This work on pre-3.1 from CVS. gcj -C does not produce any .class file gcj -c does not produce any .o file but javac (J2SDK 1.4) does not any .class file either so it seems compatible enough to me.