问题描述

string foo() { return "hello"; }
int main() 
{
    //below should be illegal for binding a non-const (lvalue) reference to a rvalue
    string& tem  = foo();   

    //below should be the correct one as only const reference can be bind to rvalue(most important const)
    const string& constTem = foo();   
}

1. GCC 是给出编译错误的好方法:从 类型的临时对象对 std::string& 类型的非常量引用无效初始化std::string
2. VS2008 还不错，至少它给出了一个编译警告:警告 C4239:使用了非标准扩展:正在初始化":从 std::string 到 std::string & 的转换 非常量引用只能绑定到左值
3. 问题来了 - VS2010(SP1) 没有任何问题错误或警告，为什么??！！我知道 VS2010 中的 rvalue reference 可用于绑定 rvalue 但我没有使用 &&，而是在演示代码中，我只是使用非常量左值引用！

1. GCC is the good one to give a compile error: invalid initialization of non-const reference of type std::string& from a temporary of type std::string
2. VS2008 is not too bad as at least it gives a compile warning: warning C4239: nonstandard extension used : 'initializing' : conversion from std::string to std::string & A non-const reference may only be bound to an lvalue
3. Here comes the problematic one - VS2010(SP1) comples fine WITHOUT any error or warning, WHY ??!! I know rvalue reference in VS2010 can be used to bind with rvalue but I am NOT using &&, instead in the demo code, I was just using non-const lvalue reference !

这里有人能帮我解释一下VS2010的行为吗?是bug吗！?谢谢

Can somone help me explain the behavior of VS2010 here? Is it a bug !? Thanks

推荐答案

这是 VS 编译器的已知问题/功能.他们一直允许这样做，并且似乎没有任何推动删除该扩展.

That is a known issue/feature of the VS compilers. They have always allowed that and there does not seem to be any push into removing that extension.

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