Do C ++ POD类型有RTTI吗？ [英] Do C++ POD types have RTTI?

问题描述

由于我理解RTTI是如何在各种C ++编译器（如GCC）中实现的，指向 type_info 数据的指针存储在

As I understand how RTTI is implemented in various C++ compilers (such as GCC), a pointer to the type_info data is stored in the vtable data of each class.

此处，POD类型可能没有 vtable 。

And also as mentioned here, POD type may not have a vtable.

但是如果POD类型可能没有 vtable ，那么指向 type_info 的指针是否存储？我知道它是实现特定的，但最好是注意一个C ++编译器（如GCC）内部。

But if POD types may not have a vtable then where is the pointer to the type_info stored? I know it is implementation-specific, but it would be better to be aware of a C++ compiler (such as GCC) internals.

推荐答案

p>有两种类型（为了RTTI的目的）：多态类型和非多态类型。多态类型是一种具有虚函数的类型，本身或继承自基类。非多态类型是其他;

There are two kinds of types (for the purposes of RTTI): polymorphic types and non-polymorphic types. A polymorphic type is a type that has a virtual function, in itself or inherited from a base class. A non-polymorphic type is everything else; this includes POD types, but it includes many other types too.

如果你有一个指向/指向一个多态类型 T ，你调用 typeid 就可以了，你回来的 type_info 不一定是 type_info ，您将返回 typeid（T {}）。相反，它是对象的 true 动态类型：最导出的类。

If you have a pointer/reference to a polymorphic type T, and you call typeid on it, the type_info you get back is not necessarily the type_info you would get back for typeid(T{}). Instead, it is the true dynamic type of the object: the most derived class.

如果你有一个指针/引用< >非 - 多态类型 T ， typeid 将始终 code> $ $ type_info 。非多态类型总是假定指针/引用是它的静态类型。

If you have a pointer/reference to a non-polymorphic type T, typeid will always return the type_info for T itself. Non-polymorphic types always assume that the pointer/reference is exactly its static type.

POD类型是非多态的，但是大量的类型是非多态的

POD types are non-polymorphic, but a huge number of types are non-polymorphic as well.

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