The conversion programs protoize and unprotoize can sometimes change a source file in a way that won't work unless you rearrange it. If this happens, protoize error messages should show you where the new references are, so fixing the file by hand is straightforward. It prints a warning whenever an argument is converted. This problem is inherent in the design of C and cannot be fixed. Unprotoize can become confused when trying to convert a function definition or declaration which contains a declaration for a pointer-to-function formal argument which has the same name as the function being defined or declared. We recommend you avoid such choices of formal parameter names. Protoize cannot get the argument types for a function whose definition was not actually compiled due to preprocessing conditionals. When this happens, protoize changes nothing in regard to such a function. One case in which you can be sure unprotoize is safe is when you are removing prototypes that were made with protoize; if the program worked before without any prototypes, it will work again without them.