C ++操作符重载 - 从类转换 [英] C++ Operator overloading - casting from class

问题描述

在将Windows代码移植到Linux时，我遇到了以下GCC 4.2.3错误消息。 （是的，我知道它是一个微小的老版本，但我不能轻易升级。）

While porting Windows code to Linux, I encountered the following error message with GCC 4.2.3. (Yes, I'm aware that it's a slight old version, but I can't easily upgrade.)

main.cpp:16: error: call of overloaded ‘list(MyClass&)’ is ambiguous
/usr/include/c++/4.2/bits/stl_list.h:495: note: candidates are: std::list<_Tp, _Alloc>::list(const std::list<_Tp, _Alloc>&) [with _Tp = unsigned char, _Alloc = std::allocator<unsigned char>]
/usr/include/c++/4.2/bits/stl_list.h:484: note:                 std::list<_Tp, _Alloc>::list(size_t, const _Tp&, const _Alloc&) [with _Tp = unsigned char, _Alloc = std::allocator<unsigned char>]

我使用以下代码来生成此错误。

I'm using the following code to generate this error.

#include <list>
class MyClass
    {
    public:
        MyClass(){}

        operator std::list<unsigned char>() const { std::list<unsigned char> a; return a; }
        operator unsigned char() const { unsigned char a; return a; }

    };

    int main()
    {
        MyClass a;
        std::list<unsigned char> b = (std::list<unsigned char>)a;

        return 0;
    }

有人遇到此错误吗？更重要的是，如何绕过它？ （可以通过使用 GetChar（）， GetList（）等函数完全避免重载，但我想避免这种情况。）

Has anyone experienced this error? More importantly, how to get around it? (It's possible to completely avoid the overload, sure, by using functions such as GetChar(), GetList() etc, but I'd like to avoid that.)

（顺便说一下，删除 operator unsigned char（）删除错误。）

(By the way, removing "operator unsigned char()" removes the error.)

推荐答案

如果删除转换，它会正确编译， :: list is being executed。

It compiles properly if you remove the cast, and I've checked that the operator std::list is being executed.

int main()
{
    MyClass a;
    std::list<unsigned char> b = a;

    return 0;
}

或者如果将它强制转换为const引用。

Or if you cast it to a const reference.

    int main()
    {
        MyClass a;
        std::list<unsigned char> b = (const std::list<unsigned char>&)a;

        return 0;
     }

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