Add freetree().

freetree() frees the allocated heap memory manually rather than relying
on the OS for garbage collection. This avoid potential memory leak
issues, which is good practice.

Author: fsaadatmand

chapter06/6-2.c

@@ -26,6 +26,7 @@ struct tnode *talloc(void);            /* alocate memory to new tree node */
 char   *strDup(char *);                /* copy string into safe place */
 struct key *binsearch(char *, struct key *, int); 
 void   findVariables(struct tnode *, int);
+struct tnode *freetree(struct tnode *);
 
 /* globals */
 char   buf[BUFSIZE];                   /* buffer from ungetch */
@@ -196,6 +197,17 @@ struct tnode *talloc(void)
 	return (struct tnode *) malloc(sizeof(struct tnode));
 }
 
+/* freetree: free allocated heap memory of node tree */
+struct tnode *freetree(struct tnode *node)
+{
+	if (node != NULL) {
+		freetree(node->left);
+		freetree(node->right);
+		free(node->word);
+		free(node);
+	}
+	return node;
+}
 /*strDup: make a duplicate of s */
 char *strDup(char *s)
 {
@@ -264,5 +276,6 @@ int main(int argc, char *argv[])
 				root = addtree(root, word);                   /* reserved words */
 	findVariables(root, nChar);
 	treeprint(root);
+	root = freetree(root);             /* clean up */
 	return 0;
 }

chapter06/6-4.c

@@ -27,6 +27,7 @@ struct tnode *addtree(struct tnode *, char *);
 void treeprint(struct tnode *);
 struct tnode *copyTree(struct tnode *, struct tnode *);
 struct tnode *sortTree(struct tnode *, struct tnode *);
+struct tnode *freetree(struct tnode *);
 
 /* globals */
 char   buf[BUFSIZE];                   /* buffer from ungetch */
@@ -134,13 +135,24 @@ struct tnode *copyTree(struct tnode *p, struct tnode *root)
 struct tnode *sortTree(struct tnode *p, struct tnode *root)
 {
 	if (root != NULL) {
-		sortTree(p, root->left);
+		p = sortTree(p, root->left);
 		p = copyTree(p, root);
-		sortTree(p, root->right);
+		p = sortTree(p, root->right);
 	}
 	return p;
 }
 
+/* freetree: free allocated heap memory of node tree */
+struct tnode *freetree(struct tnode *node)
+{
+	if (node != NULL) {
+		freetree(node->left);
+		freetree(node->right);
+		free(node->word);
+		free(node);
+	}
+	return node;
+}
 int main(void)
 {
 	struct tnode *root;                /* root node */
@@ -154,5 +166,7 @@ int main(void)
 			root = (addtree(root, word));
 	sRoot = sortTree(sRoot, root);
 	treeprint(sRoot);
+	root = freetree(root);             /* clean up */
+	sRoot = freetree(sRoot);           /* clean up */
 	return 0;
 }