We pass the outputStream to much more debug routines than openJDK does, as we write a lot more information to files e.g., in case of a crash. I would like to contribute the changes that allow to pass the output stream to node->dump() and everything reachable from there. This also fixes the usage of output stream in print_register_type() in oopMap.cpp and in MachNullCheckNode::format(), where a single print command still used tty. Further we initialize _node_regs_max_index so that node_regs_max_index() == 0 indicates that registers of a node can be accessed. This is also useful in debug output. http://cr.openjdk.java.net/~goetz/webrevs/webrev-os_in_nodeDump/ Best regards, Goetz.