structs

[Mini]

Hello,

If a have structs like:

struct queueNodeInfo {
   int ID;
   int arr[MAX];
};

typedef struct queueNodeInfo QueueNodeInfo;
typedef QueueNodeInfo *QueueNodeInfoPtr;

struct queueNode {
   struct queueNodeInfo Info;
   struct queueNode *nextPtr;
};

typedef struct queueNode QueueNode;
typedef QueueNode *QueueNodePtr;

and say I do something like:

void enqueue( QueueNodePtr *headPtr, QueueNodePtr *tailPtr, QueueNodeInfo node ) {
   QueueNodePtr newPtr;
//   QueueNodeInfo temp;

   newPtr = malloc( sizeof( QueueNode ) );

   if ( newPtr != NULL ) { /* is space available */
//      temp=newPtr->busInfo;
      newPtr->busInfo = node;

      // free temp??

      newPtr->nextPtr = NULL;

      /* if empty, insert node at head */
      if ( isEmpty( *headPtr ) ) {
         *headPtr = newPtr;
      }
      else {
         ( *tailPtr )->nextPtr = newPtr;
      }

      *tailPtr = newPtr;
   }
   else {
      printf( "No memory available.\n" );
   }

}

Do I then need to free 'temp' as I've defined in my function? ie. Because when I run malloc, wouldn't I allocate memory for an empty 'Info' struct? If I want to assign another such struct in its place; then wouldn't I have to free the empty one? If so how would I go about doing it because free(temp) yields a compilation error...

Thanks

[Salem]

What do you mean "free yeilds a compilation error"?

I can see why calling free() at the wrong time can easily result in a segfault at RUN TIME, but that's a completely different problem to say "undefined symbol" at compile time.

Be specific and post actual error messages.

[Salem]

What do you mean "free yeilds a compilation error"?

I can see why calling free() at the wrong time can easily result in a segfault at RUN TIME, but that's a completely different problem to say "undefined symbol" at compile time.

Be specific and post actual error messages.

[Mini]

If I do free(temp); then I get "error: incompatible type for argument 1 of 'free'" whereas if I do free(&temp); then I get no error msgs, but I don't see why I need to do the latter...

Thanks

[rags_to_riches]

You do not need to free temp, as you've declared it to be an automatic stack-based variable. You only need to free pointers to heap memory, created through malloc/calloc/realloc.

[Mini]

But I have used malloc here: newPtr = malloc( sizeof( QueueNode ) );

Since I am assigning a new pointer instead of the empty one which had been created (ie. for 'Info'), wouldn't I need to free the empty one that had been created as a result?

Thanks