c - 列表 ADT - 如何释放结构指针及其成员？

Question

下面是一个列表 ADT，

typedef struct List{
  void **array;

  /* Following members for Housekeeping - Array enhancement*/
  int lastItemPosition;
  int size;
}List;
#define INITIAL_LIST_SIZE 50

<小时/>

createList 操作尝试 free(*(list->array)) ，期望仅释放 void* 的数组，但不释放指向每个 void* 的对象，因为 listPointer 获取 list

的浅拷贝

List *createList(List *list, Op opType){

  List *listPointer = (List *)malloc(sizeof(List));
  void *accumulator = NULL;
  if(opType == CREATE_NEW_LIST){

    accumulator = malloc(INITIAL_LIST_SIZE*sizeof(void*));
    listPointer->array = &accumulator;

    /* Is it safe to initialise zero to  element of array of void* pointers? */
    listPointer->array = memset(listPointer->array, 0, INITIAL_LIST_SIZE*sizeof(void *));

    listPointer->lastItemPosition = -1;
    listPointer->size = INITIAL_LIST_SIZE;
  }else if(opType == DOUBLE_THE_LIST){

    accumulator = malloc(2*(list->size)*sizeof(void *));
    listPointer->array = &accumulator;

    /* Performing shallow copy, Is deep copy required? */
    listPointer->array = memcpy(listPointer->array, list->array, list->size*sizeof(void*));

    listPointer->lastItemPosition = list->lastItemPosition;;
    listPointer->size = 2*(list->size);

    free(*(list->array)); // How to free  list pointer and its members?

  }else if(opType == HALF_THE_LIST){

    accumulator = malloc(((list->size)/2)*sizeof(void *));
    listPointer->array = &accumulator;

    /* Performing shallow copy, Is deep copy required? */
    listPointer->array = memcpy(listPointer->array, list->array, (list->size/2)*sizeof(void *));
    listPointer->lastItemPosition = list->lastItemPosition;
    listPointer->size = (list->size)/2;

    free(*(list->array)); // How to free  list pointer and its members?
  }

  return listPointer;

}

<小时/>

执行以下列表操作List，

void insertItem(List *, void *newItem);
void deleteItem(List *, int listIndex);

用户访问，

/* main.c */

#include"list.h"

int main(void){
  List *arrayList = createList((List *)NULL, CREATE_NEW_LIST);


  if (arrayList == (List *)NULL){
    fprintf(stderr, "Unable to createList() \n");
    exit(1); //Nothing else to do without arrayList
  }

  /* Objects should be on heap */
  int *object = malloc(sizeof(int));

  *object = 650;


  insertItem(arrayList, object);
}

<小时/>

问题:

您能否澄清一下，free(*(list->array)) 在我的代码中做了什么？

Answer 1

以下代码片段应该可以完成这项工作:

else if(opType == DOUBLE_THE_LIST){

    listPointer->array = realloc(listPointer->array, 2*(list->size)*sizeof(void *));

    listPointer->lastItemPosition = list->lastItemPosition;;
    listPointer->size = 2*(list->size);

    // do not free any more: free(*(list->array)); // How to free  list pointer and its members?
}