seen with 4.4 and 4.5 (attachment in PR42698), when the file fiven with -fsource-filename doesn't exist.
$ gcj-4.4 -c -fsource-filename=/tmp/fileTkf0Hh -g -O2 -fPIC -findirect-dispatch -fjni ./debian/ant-gcj/usr/lib/gcj/ant-1.7.1.jar.3.jar -o ant-1.7.1.jar.3.o
jc1: internal compiler error: in java_read_sourcefilenames, at java/jcf-parse.c:192
Please submit a full bug report,
with preprocessed source if appropriate.
Closing as won't fix as the Java front-end has been removed from the trunk.