函数属性是否被继承? [英] Are function attributes inherited?

问题描述

如果我有一个带有属性

[[nodiscard]]
virtual bool some_function() = 0;

该属性是否隐式应用于该函数的替代?

Does that attribute get implicitly applied to overrides of that function?

bool some_function() override;

还是我需要再次使用该属性?

Or do I need the attribute again?

[[nodiscard]]
bool some_function() override;

推荐答案

在C ++ 17的措辞中，我看不到任何证据表明属性是由重写函数继承的.

I can't see any evidence in the C++17 wording that attributes are inherited by overriding functions.

我能找到的最相关的部分是覆盖规则:

The most relevant section I can find is the rules for overriding:

[class.virtual]/2:如果在类Base和类Derived中声明了虚拟成员函数vf，这些成员函数直接或间接从Base派生，则成员函数vf具有相同名称，参数类型列表(11.3.5)， cv限定和 ref-qualifier (或不存在)与Base::vf相同)，那么Derived::vf也是虚拟的(无论是否声明)，并且覆盖 Base::vf. [..]

[class.virtual]/2: If a virtual member function vf is declared in a class Base and in a class Derived, derived directly or indirectly from Base, a member function vf with the same name, parameter-type-list (11.3.5), cv-qualification, and ref-qualifier (or absence of same) as Base::vf is declared, then Derived::vf is also virtual (whether or not it is so declared) and it overrides Base::vf. [..]

尽管这段话从一个稍微不同的角度解决了这个问题，但我认为足以证明仅继承了虚拟性(并且在确定一个功能是否覆盖另一个功能时，属性根本不起作用).话虽这么说，但我认为这没有被充分说明，至少可以做一个澄清的说明.

While this passage attacks the problem from a slightly different angle, I think it's enough to show that only virtualness is "inherited" (and that attributes don't come into play at all when deciding whether one function overrides another). That being said, I think this is slightly underspecified and could do with a clarifying note at the very least.

当然，这很快变得复杂起来.给出以下示例:

Of course, this quickly gets complicated. Given the below example:

struct B {
    [[nodiscard]] virtual bool foo() { return true; }
};

struct D : B {
    bool foo() override { return false; }
};

int main() {
    D().foo();
}

Clang不会发出警告.但是，可以通过基本指针访问该函数.

Clang will not issue a warning. However, access the function through a base pointer and it will.

struct B {
    [[nodiscard]] virtual bool foo() { return true; }
};

struct D : B {
    bool foo() override { return false; }
};

int main() {
    D d;
    ((B*)&d)->foo();
}

我不确定这是什么意思.

What that means for your question, I'm not sure.

再次，我想从标准中获得更多有关此主题的指导.

Again, I'd like to see a bit more guidance from the standard on this topic.

这篇关于函数属性是否被继承?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！