/* Check if tempfile "path" exists, and if so, exit with explanation that. */
extern void check_tempfile(char * path);
/* If one and only one of files at "p1", "p2" exists, fail with explanation. */
extern void check_files_xor(char * p1, char * p2);
/* Check if tempfile "path" exists, and if so, exit with explanation that. */
extern void check_tempfile(char * path);
/* If one and only one of files at "p1", "p2" exists, fail with explanation. */
extern void check_files_xor(char * p1, char * p2);