In util/makedefs.c is the source for a program called makedefs. When you build a copy of NetHack, it uses makedefs to generate date.h, onames.h, pm.h, vis_tab.h, and vis_tab.c. This explains why those files are missing from an unbuilt copy of the source code. In the Unix Makefiles, makedefs is called from the Makefiles in the src and util directories. makedefs accepts the following commandline parameters: