diff --git a/include/r3_str.h b/include/r3_str.h
index 0250144..469ef9d 100644
--- a/include/r3_str.h
+++ b/include/r3_str.h
@@ -27,31 +27,6 @@ void str_repeat(char *s, const char *c, int len);
 
 void print_indent(int level);
 
-
-#if _GNU_SOURCE || POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700 || __DARWIN_C_LEVEL >= 200809L
-#ifndef HAVE_STRNDUP
-#define HAVE_STRNDUP
-#endif
-#endif
-
-#if _SVID_SOURCE || _BSD_SOURCE \
-    || _XOPEN_SOURCE >= 500 \
-    || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED \
-    || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L \
-    || __DARWIN_C_LEVEL >= 200809L
-#ifndef HAVE_STRDUP
-#define HAVE_STRDUP
-#endif
-#endif
-
-#ifndef HAVE_STRDUP
-char *strdup(const char *s);
-#endif
-
-#ifndef HAVE_STRNDUP
-char *strndup(const char *s, int n);
-#endif
-
 #ifdef __cplusplus
 }
 #endif