diff -Naur vdr-2.4.1.orig/tools.h vdr-2.4.1/tools.h
--- vdr-2.4.1.orig/tools.h	2020-03-23 18:30:23.199333734 +0100
+++ vdr-2.4.1/tools.h	2020-03-23 18:30:49.174333734 +0100
@@ -406,7 +406,9 @@
 private:
   DIR *directory;
   struct dirent *result;
-#if !__GLIBC_PREREQ(2, 24) // readdir_r() is deprecated as of GLIBC 2.24
+//#if !__GLIBC_PREREQ(2, 24) // readdir_r() is deprecated as of GLIBC 2.24
+#if !defined(__GLIBC__) || \
+  (defined(__GLIBC__) && (!__GLIBC_PREREQ(2, 24)) || !defined(_GNU_SOURCE))
   union { // according to "The GNU C Library Reference Manual"
     struct dirent d;
     char b[offsetof(struct dirent, d_name) + NAME_MAX + 1];