};
extern struct sha1file *sha1fd(int fd, const char *name);
-extern struct sha1file *sha1create(const char *fmt, ...);
+extern struct sha1file *sha1create(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
extern int sha1close(struct sha1file *, unsigned char *, int);
extern int sha1write(struct sha1file *, void *, unsigned int);
extern int sha1write_compressed(struct sha1file *, void *, unsigned int);