4 files changed, 30 insertions, 20 deletions

diff --git a/dlist.c b/dlist.c
index a2a5cfd..32258e8 100644
--- a/dlist.c
+++ b/dlist.c
@@ -112,7 +112,9 @@ dlist_pop_front(struct dlist *dlist, T *data)
                 else
                         element->next->prev = NULL;
 
-                *data = element->data;
+                if ( data != NULL ) {
+                        *data = element->data;
+                }
                 free(element);
 
                 return true;
@@ -134,7 +136,9 @@ dlist_pop_back(struct dlist *dlist, T *data)
                 else
                         element->prev->next = NULL;
 
-                *data = element->data;
+                if ( data != NULL ) {
+                        *data = element->data;
+                }
                 free(element);
 
                 return true;
diff --git a/queue.c b/queue.c
index e26acbb..2fb9c72 100644
--- a/queue.c
+++ b/queue.c
@@ -47,7 +47,10 @@ queue_get(struct queue *queue, T *data)
 {
         if ( queue->head != NULL ) {
                 struct queue_item *next = queue->head->next;
-                *data                   = queue->head->data;
+
+                if ( data != NULL ) {
+                        *data = queue->head->data;
+                }
                 free(queue->head);
                 queue->head = next;
 
diff --git a/stack.c b/stack.c
index fa89974..775269d 100644
--- a/stack.c
+++ b/stack.c
@@ -1,7 +1,7 @@
 /* Standard C */
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdbool.h>
 
 /* Project */
 #include "util.h"
@@ -10,7 +10,7 @@ typedef int T;
 
 struct stack_item {
         struct stack_item *next;
-        T data;
+        T                  data;
 };
 
 struct stack {
@@ -31,7 +31,7 @@ stack_push(struct stack *stack, T data)
         if ( (new_item = malloc(sizeof(*new_item))) != NULL ) {
                 new_item->data = data;
                 new_item->next = stack->head;
-                stack->head = new_item;
+                stack->head    = new_item;
         }
         else
                 ERROR("out of memory");
@@ -42,7 +42,10 @@ stack_pop(struct stack *stack, T *data)
 {
         if ( stack->head != NULL ) {
                 struct stack_item *next = stack->head->next;
-                *data = stack->head->data;
+
+                if ( data != NULL ) {
+                        *data = stack->head->data;
+                }
                 free(stack->head);
                 stack->head = next;
 
@@ -93,6 +96,3 @@ main()
 
         return EXIT_SUCCESS;
 }
-
-
-
diff --git a/stack2.c b/stack2.c
index 57dce4f..4c77ac2 100644
--- a/stack2.c
+++ b/stack2.c
@@ -1,13 +1,13 @@
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <stdbool.h>
 
 #include "util.h"
 
 typedef int T;
 
 struct stack {
-        T *array;
+        T *    array;
         size_t sz, p;
 };
 
@@ -15,8 +15,8 @@ void
 stack_init(struct stack *stack)
 {
         stack->array = NULL;
-        stack->sz = 0;
-        stack->p = 0;
+        stack->sz    = 0;
+        stack->p     = 0;
 }
 
 bool
@@ -25,7 +25,7 @@ stack_push(struct stack *stack, T data)
         if ( stack->array == NULL ) {
                 if ( (stack->array = malloc(10 * sizeof(*stack->array))) != NULL ) {
                         stack->sz = 10;
-                        stack->p = 0;
+                        stack->p  = 0;
                 }
                 else {
                         ERROR("out of memory");
@@ -35,11 +35,11 @@ stack_push(struct stack *stack, T data)
 
         if ( stack->p == stack->sz ) {
                 size_t new_sz;
-                T *new_array;
+                T *    new_array;
 
-                if ( (new_array = realloc(stack->array, (new_sz = (stack->sz * 3 / 2)) * sizeof(*stack->array))) != NULL ) {
+                if ( (new_array = realloc(stack->array, (new_sz = (stack->sz * 3 / 2)) * sizeof(*stack->array))) != NULL ) {
                         stack->array = new_array;
-                        stack->sz = new_sz;
+                        stack->sz    = new_sz;
                 }
                 else {
                         ERROR("out of memory");
@@ -55,7 +55,11 @@ bool
 stack_pop(struct stack *stack, T *data)
 {
         if ( stack->p != 0 ) {
-                *data = stack->array[--stack->p];
+                --stack->p;
+
+                if ( data != NULL ) {
+                        *data = stack->array[stack->p];
+                }
                 return true;
         }
         else
@@ -97,4 +101,3 @@ main()
 
         return EXIT_SUCCESS;
 }
-