Fixed forward defragmenting, added reverse defragmenting, and added a line break on second printf.

main.c

@@ -9,6 +9,7 @@
 struct block
 {
 	size_t size;
+	struct block* prev;
 	struct block* next;
 	int free;
 };
@@ -27,6 +28,7 @@ struct block* extend_heap(size_t s)
 		return NULL;
 
 	b->size = s;
+	b->prev = last;
 	b->next = NULL;
 	b->free = 0;
 
@@ -87,7 +89,6 @@ void* malloc(size_t size)
 /// Will flag the provided memory as free and will defragment other blocks adjacent to it.
 /// @param [in] ptr The memory to flag as free.
 /// @note If all data after the provided memory is free, it will reduce the heap size.
-/// @todo Reverse defragmenting.
 void free(void* ptr)
 {
 	if (!ptr)
@@ -96,15 +97,15 @@ void free(void* ptr)
 	struct block* b = (struct block*)ptr - 1;
 	b->free = 1;
 
-	struct block* link = b->next;
+	while (b->prev && b->prev->free)
+		b = b->prev;
+
 	while (b->next && b->next->free)
 	{
 		b->size += BLOCK_SIZE + b->next->size;
-		b->next = link->next;
+		b->next = b->next->next;
 	}
 
-	// Reverse defragment here.
-
 	if (!b->next)
 		brk(b);
 }
@@ -118,10 +119,10 @@ int main()
 	*b = 12;
 
 	printf("Test 1: %i\n", *a);
-	printf("Test 2: %i", *b);
+	printf("Test 2: %i\n", *b);
 
-	free(b);
 	free(a);
+	free(b);
 
 	return 0;
 }