I just tried to compile package pcb-1.6.3-1068 with a prerelease version
of GNU C compiler 4.1.

It said

rats.c:220: warning: "thefp" is used uninitialized in this function

The offending source code is

        FILE                    *thefp;

        MyFree(&command);
        command = EvaluateFilename(Settings.RatCommand, Settings.RatPath, filename, NULL);

                /* open pipe to stdout of command */
        if (*command == '\0' || (thefp = popen(command, "r")) == NULL)
        {
                PopenErrorMessage(command);
        }
                return(thefp);


If *command == '\0', then thefp contains rubbish, which is then returned
to the caller. Suggest initialise local variable "thefp" before first use.

BTW, the address of the author [ Thomas.Nau@rz.uni-ulm.de ] does not seem to work.