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C++不同平台下的RTTI实现

article 2024/9/27 19:27:52

给定一个含有虚函数的对象的地址，找到对应的类名，不同平台下方法也不同，这是由于RTTI实现并没有统一的标准。

Linux：

Linux

#include <iostream>
#include <typeinfo>

class Person
{
public:
    virtual void func()
    {
        std::cout << typeid(*this).name() << std::endl;
    }
};

const char* ClassName(void* address)
{
    uintptr_t* objPtr = reinterpret_cast<uintptr_t*>(address);
    uintptr_t* vftablePtr = reinterpret_cast<uintptr_t*>(*objPtr);
    std::type_info* ti = reinterpret_cast<std::type_info*>(*(vftablePtr - 1));
    return ti->name();
}

int main()
{
    Person p;
    std::cout << ClassName(&p) << std::endl;
    std::cout << typeid(p).name() << std::endl;
}

运行结果：

6Person
6Person

其中，Person代表类名，6表示的是类名的长度。

Windows x86：

Windows x86

#include <iostream>
#include <typeinfo>

class Person
{
public:
    virtual void func()
    {
        std::cout << typeid(*this).name() << std::endl;
    }
};

const char* ClassMangledName(void* address)
{
    uintptr_t* objPtr = reinterpret_cast<uintptr_t*>(address);
    uintptr_t* vftablePtr = reinterpret_cast<uintptr_t*>(*objPtr);
    uintptr_t* rttiObject = reinterpret_cast<uintptr_t*>(*(vftablePtr - 1));
    std::type_info* ti = reinterpret_cast<std::type_info*>(*(rttiObject + 3));

    const char* className = ti->name();
    return className;
}

int main()
{
    Person p;
    std::cout << ClassMangledName(&p) << std::endl;
    std::cout << typeid(p).name() << std::endl;
}

运行结果：

class Person
class Person

Windows x64：

Windows x64

#include <iostream>
#include <ehdata.h>
#include <rttidata.h>

class Person
{
public:
    virtual void func()
    {
        std::cout << typeid(*this).name() << std::endl;
    }
};

const char* ClassMangledName(void* address)
{
    uintptr_t* objPtr = reinterpret_cast<uintptr_t*>(address);
    uintptr_t* vftablePtr = reinterpret_cast<uintptr_t*>(*objPtr);
    _RTTICompleteObjectLocator* rttiLocator = reinterpret_cast<_RTTICompleteObjectLocator*>(*(vftablePtr - 1));
    uintptr_t imageBase = reinterpret_cast<uintptr_t>(rttiLocator) - rttiLocator->pSelf;
    TypeDescriptor* typeDescriptor = reinterpret_cast<TypeDescriptor*>(imageBase + rttiLocator->pTypeDescriptor);

    const char* classMangledName = typeDescriptor->name;
    return classMangledName;
}

int main()
{
    Person p;
    std::cout << ClassMangledName(&p) << std::endl;
    std::cout << typeid(p).raw_name() << std::endl;
}