std::is_standard_layout

• has no virtual functions and no virtual base classes.
• has the same access control (private, protected, public) for all its non-static data members.
• either has no non-static data members in the most derived class and at most one base class with non-static data members, or has no base classes with non-static data members.
  
• its base class (if any) is itself also a standard-layout class. And,
• has no base classes of the same type as its first non-static data member.

模板参数

T

一个完整类型，或者void(possible cv-qualified), or an array of unknown bound of a complete element type.

成员类型

成员常量

成员函数

operator bool

Returns value (public member function)

示例

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// is_standard_layout example
#include <iostream>
#include <type_traits>

struct A { int i; };

struct B : A { int j; };

int main() {
  std::cout << std::boolalpha;
  std::cout << "is_standard_layout:" << std::endl;
  std::cout << "int: " << std::is_standard_layout<int>::value << std::endl;
  std::cout << "A: " << std::is_standard_layout<A>::value << std::endl;
  std::cout << "B: " << std::is_standard_layout<B>::value << std::endl;
  return 0;
}

is_standard_layout:
int: true
A: true
B: false

另见

is_pod

是否为 POD 类型 （类模板）

is_trivial

是否为平凡类型 （类模板）

is_trivially_copyable

是否为平凡可复制 （类模板）