free the space allocated in c with malloc

c, free, malloc, struct, typedef

Solution

That is correct.

To help avoid shooting yourself in the foot, you might consider the following practices:

- Always free all malloc/calloc'ed memory with free()

- Afterwards, set the pointer to NULL

- Use a dedicated cleanup/destroy function to ensure consistent memory cleanup

The following function would be a good way to make sure you always cleanup a structure properly, avoid memory leaks, and avoid accidentally freeing already-freed memory and causing a segmentation fault:

int destroyNode(Node* myNode) {
  if(!myNode) {
    printf("Invalid pointer! Exiting");
    return (-1);
  }

  // Clear out memory
  if(np) {
    free(np);
    np = NULL;
  }
  if(R) {
    free(R);
    R = NULL;
  }
  if(C) {
    free(C);
    C = NULL;
  }
  if(ptrTempLst) {
    free(ptrTempLst);
    ptrTempLst = NULL;
  }
  if(leftTree) {
    free(leftTree);
    leftTree = NULL;
  }
  if(rightTree) {
    free(rightTree);
    rightTree = NULL;
  }

  free(myNode);
}

eg:

int main(void) {
  Node *tempNode = calloc((size_t)1,sizeof(Node));

  // Alloc the member nodes, etc, do some code


  // Ready to clean up and exit program
  destroyNode(tempNode);
  tempNode = NULL;

  return 0;
}

Good luck!

Problem

I have a question about this code: ``` typedef struct pop { unsigned long int *np; // matrix unsigned long int f; long double fp; unsigned long int *R; // matrix unsigned long int *C; // matrix unsigned long int Dp; unsigned long int Ds; unsigned long int count; struct popolazione *ptrTempLst; // pointer struct popolazione *leftTree; // left tree pointer struct popolazione *rightTree; // right tree pointer } Node; ``` When I free space allocated for this struct, prior have I to free pointer to matrix inside struct? For example, ``` Node *ptr=(Node *) malloc(sizeOf(Node)); ptr->np=(unsigned long int *)malloc(10*sizeOf(unsigned long int)); /*code code code*/ // is necessary: free(ptr->np); free(ptr); ``` Thanks in advance

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