search: add tdestroy (gnu extension)

include/search.h

@@ -38,6 +38,8 @@ struct qelem {
 	struct qelem *q_forw, *q_back;
 	char q_data[1];
 };
+
+void tdestroy(void *, void (*)(void *));
 #endif
 
 #ifdef __cplusplus

src/search/tdestroy.c

@@ -0,0 +1,21 @@
+#define _GNU_SOURCE
+#include <stdlib.h>
+#include <search.h>
+
+struct node {
+	void *key;
+	struct node *left;
+	struct node *right;
+};
+
+void tdestroy(void *root, void (*freekey)(void *))
+{
+	struct node *r = root;
+
+	if (r == 0)
+		return;
+	tdestroy(r->left, freekey);
+	tdestroy(r->right, freekey);
+	freekey(r->key);
+	free(r);
+}