-int BIO_printf(BIO *bio, const char *format, ...);
-int BIO_snprintf(char *buf, size_t n, const char *format, ...);
+#ifndef __GNUC__
+#define __attribute__(x)
+#endif
+int BIO_printf(BIO *bio, const char *format, ...)
+ __attribute__((__format__(__printf__,2,3)));
+int BIO_vprintf(BIO *bio, const char *format, va_list args)
+ __attribute__((__format__(__printf__,2,0)));
+int BIO_snprintf(char *buf, size_t n, const char *format, ...)
+ __attribute__((__format__(__printf__,3,4)));
+int BIO_vsnprintf(char *buf, size_t n, const char *format, va_list args)
+ __attribute__((__format__(__printf__,3,0)));