带有空指针的二维指针数组
2D array of pointers c++ with null pointers
如何在 C++ 中声明一个二维指针数组并通过空指针对其进行初始化？
我试过这样做
int *arr[20][30]= nullptr;
你可以aggregate initialize初始化列表为空的数组，
int *arr[20][30] {};
// or
int *arr[20][30] = {};
（强调我的）
If the number of initializer clauses is less than the number of members and bases (since C++17) or initializer list is completely empty, the remaining members and bases (since C++17) are initialized by their default member initializers, if provided in the class definition, and otherwise (since C++14) by empty lists, in accordance with the usual list-initialization rules (which performs value-initialization for non-class types and non-aggregate classes with default constructors, and aggregate initialization for aggregates).
那么arr的所有元素（即子数组int* [30]）就是aggregate-initialized with empty initializer list too, then all the elements of sub-array with type int* would be value-initialized,
otherwise, the object is zero-initialized.
最后 int* 类型（内置类型）的元素全部零初始化为空指针。
If T is a scalar type, the object's initial value is the integral constant zero explicitly converted to T.
如何在 C++ 中声明一个二维指针数组并通过空指针对其进行初始化？
我试过这样做
int *arr[20][30]= nullptr;
你可以aggregate initialize初始化列表为空的数组，
int *arr[20][30] {};
// or
int *arr[20][30] = {};
（强调我的）
If the number of initializer clauses is less than the number of members
and bases (since C++17)or initializer list is completely empty, the remaining membersand bases (since C++17)are initializedby their default member initializers, if provided in the class definition, and otherwise (since C++14)by empty lists, in accordance with the usual list-initialization rules (which performs value-initialization for non-class types and non-aggregate classes with default constructors, and aggregate initialization for aggregates).
那么arr的所有元素（即子数组int* [30]）就是aggregate-initialized with empty initializer list too, then all the elements of sub-array with type int* would be value-initialized,
otherwise, the object is zero-initialized.
最后 int* 类型（内置类型）的元素全部零初始化为空指针。
If
Tis a scalar type, the object's initial value is the integral constant zero explicitly converted toT.