gnu search.h has struct qelem...

include/search.h

@@ -33,6 +33,13 @@ void *tfind(const void *, void *const *, int(*)(const void *, const void *));
 void *tsearch(const void *, void **, int (*)(const void *, const void *));
 void twalk(const void *, void (*)(const void *, VISIT, int));
 
+#ifdef _GNU_SOURCE
+struct qelem {
+	struct qelem *q_forw, *q_back;
+	char q_data[1];
+};
+#endif
+
 #ifdef __cplusplus
 }
 #endif