I have another iteration of this change http://cr.openjdk.java.net/~martin/webrevs/openjdk8/hide-zlib/ that adds exciting new exception detail message for the InternalError I was scratching my head about earlier.
- msg = strm->msg; + msg = ((strm->msg != NULL) ? strm->msg : + (ret == Z_VERSION_ERROR) ? + "zlib returned Z_VERSION_ERROR: " + "compile time and runtime zlib implementations differ" : + (ret == Z_STREAM_ERROR) ? + "inflateInit2 returned Z_STREAM_ERROR" : + "unknown error initializing zlib library");