constexpr默认的默认构造函数 [英] constexpr defaulted default constructors

问题描述

如果我想将我的 default -ed默认构造函数声明为 constexpr ，则Clang 3.8和GCC 5.3会出现编译器错误.根据此 stackoverflow问题，它应该可以正常工作:

I get compiler error by Clang 3.8 and GCC 5.3 if I want to declare my default-ed default constructors as constexpr. According to this stackoverflow question it just should work fine:

struct A
{
    constexpr A() = default;

    int x;
};

但是:

Error: defaulted definition of default constructor is not constexpr

您是否知道实际发生了什么?

Have you got any clue what is actually going on?

推荐答案

按现状，x仍未初始化，因此无法在编译时构造该对象.

As it stands, x remains uninitialized, so the object can not be constructed at compile time.

您需要初始化x:

struct A
{
    constexpr A() = default;

    int x = 1;
};

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