指向指针取消引用的指针；编译器要求'->'

Question

我编写了一个简单的函数来将子列表插入到通过引用给出的链表中。代码对我来说看起来是正确的，但编译器指示我没有正确使用指针。

void insertSub(string h, day d, string gr, string sub, ListAPI **tmp_api) {
  auto newNode = new _ListSub;

  // initialize new node of sub-list
  newNode->h = h;
  newNode->d = d;
  newNode->gr = gr;
  newNode->sub = sub;

  // point new node to the previous and next node
  newNode->next = node->next;
  newNode->prev = node;

  // point actual node to the new node
  *tmp_api->head->next->prev = newNode;
  *tmp_api->head->next = newNode;

  cout << "New node inserted to " << *tmp_api->id << endl;

  // increment size
  ++ node->size;
}

在一些调用者函数中，我像这样使用它：

auto tmp_api = api;
insertSub( h, (day)enumerateDay(week), gr, sub, &tmp_api );

其中 api 属于 ListAPI * 类型并且确实包含节点。

g++ 错误：

../src/main.cpp:107:13: error: request for member ‘head’ in ‘* tmp_api’, which is of pointer type ‘ListAPI*’ (maybe you meant to use ‘->’ ?)
   *tmp_api->head->next->prev = newNode;
             ^~~~
../src/main.cpp:108:13: error: request for member ‘head’ in ‘* tmp_api’, which is of pointer type ‘ListAPI*’ (maybe you meant to use ‘->’ ?)
   *tmp_api->head->next = newNode;
             ^~~~
../src/main.cpp:110:51: error: request for member ‘id’ in ‘* tmp_api’, which is of pointer type ‘ListAPI*’ (maybe you meant to use ‘->’ ?)
   cout << "  $ newNode inserted to " << *tmp_api->id << endl;

Answer 1

如 here 所示，-> 运算符的优先级高于 * 运算符，因此它首先被评估。使用 (*temp_api)->head.

指向指针取消引用的指针；编译器要求'->'

Pointer to pointer dereference; Compiler asking for '->'

c++

pointers

dereference