[libc] add n versions of sprintf and vprintf
diff --git a/include/printf.h b/include/printf.h
index 5006530..2d09120 100644
--- a/include/printf.h
+++ b/include/printf.h
@@ -33,7 +33,9 @@
int printf(const char *fmt, ...);
int sprintf(char *str, const char *fmt, ...) __PRINTFLIKE(2, 3);
+int snprintf(char *str, size_t len, const char *fmt, ...) __PRINTFLIKE(3, 4);
int vsprintf(char *str, const char *fmt, va_list ap);
+int vsnprintf(char *str, size_t len, const char *fmt, va_list ap);
#if defined(__cplusplus)
}