Strange messages sent to stderr when using a fastdebug JDK build

I'm seeing all kinds of messages like: bit length overflow code 12 bits 6->7 bit length overflow code 5 bits 6->7 bit length overflow code 5 bits 6->7 When ever a jdk7u or jdk8 fastdebug built jdk is used. It appears to be coming from here: jdk/src/share/native/java/util/zip/zlib-1.2.5/trees.c: Trace((stderr,"\nbit length overflow\n")); These stderr messages get folded into the java users stderr... I don't think we want that. -kto