+#define REENTR_H
+
+/* If compiling for a threaded perl, we will macro-wrap the system/library
+ * interfaces (e.g. getpwent()) which have threaded versions
+ * (e.g. getpwent_r()), which will handle things correctly for
+ * the Perl interpreter, but otherwise (for XS) the wrapping does
+ * not take place. See L<perlxs/Thread-aware system interfaces>.
+ */
+
+#ifndef PERL_REENTR_API
+# if defined(PERL_CORE) || defined(PERL_EXT)
+# define PERL_REENTR_API 1
+# else
+# define PERL_REENTR_API 0
+# endif
+#endif