成员初始化列表是否没有定义值？
Is a member initialization list without a value defined?
说我有 :
class Foo
{
public:
int x;
Foo() : x() {}
}
构造函数有运行后读x会不会是UB？更具体地说，这是什么类型的初始化，零初始化、直接初始化还是默认初始化？
我知道如果我们有：
Foo() : x(42) {}
x 会直接初始化为 42 但我不太确定上面的代码片段，如果结果是这样，我不想被 UB 狼咬默认初始化。
what type of initialization is this
x() 执行 value-initialization:
when a non-static data member or a base class is initialized using a member initializer with an empty pair of parentheses or braces (since C++11);
作为非class类型int，x最终被零初始化为0。
- otherwise, the object is zero-initialized.
说我有 :
class Foo
{
public:
int x;
Foo() : x() {}
}
构造函数有运行后读x会不会是UB？更具体地说，这是什么类型的初始化，零初始化、直接初始化还是默认初始化？
我知道如果我们有：
Foo() : x(42) {}
x 会直接初始化为 42 但我不太确定上面的代码片段，如果结果是这样，我不想被 UB 狼咬默认初始化。
what type of initialization is this
x() 执行 value-initialization:
when a non-static data member or a base class is initialized using a member initializer with an empty pair of parentheses
or braces (since C++11);
作为非class类型int，x最终被零初始化为0。
- otherwise, the object is zero-initialized.