C++函数返回引用和值问题

今天因为改到一个代码，所以遇到一个问题。函数里局部变量返回的问题。

以下是代码，就是运用类模板，重载了+操作：

一。最原始的代码如下：

<pre name="code" class="cpp">#include<iostream>
#include<cstdlib>
template<typename T>
class T_Counter
{
public:
T_Counter(T aa)
{a=aa;
}
T_Counter()
{a=0;
}
~T_Counter()
{cout<<"T_Counter "<<a<<" destruct!"<<endl;
};


T_Counter<T>& operator +(const T_Counter<T> t)
{T_Counter<T> temp;temp.a=a+t.a;return temp;
}friend ostream& operator<<(ostream &output,T_Counter<T>& t)
{output<<t.a;return output;
}
friend istream& operator>>(istream &input,T_Counter<T> &t)
{input>>t.a;return input;
}private:T a;
};int main()
{T_Counter<int> a(100),b(20);

<span style="white-space:pre">  </span>c = a+b;cout<<c<<endl;
}

在win7+VS2012下可以编译通过，结果如下：

<pre name="code" class="cpp">T_Counter 120 destruct!

<pre name="code" class="cpp">T_Counter 20 destruct!

120
T_Counter 120 destruct!
T_Counter 20 destruct!
T_Counter 100 destruct!

我的理解是：首先输入参数是传值，那么首先会创建一个局部变量来接收传入的值，也就是t。接下来就是构造temp。所以前两行就是因为在<pre name="code" class="cpp">T_Counter<T>& operator +(const T_Counter<T> t)返回前销毁了两个临时变量，调用了相应的析构函数。但是这里的返回引用就有问题，因为

返回引用其实也就是返回临时变量temp的地址，但是因为temp地址所指向的东西在return前已经被销毁了。这样肯定会出错，但却运行正常。

但是这段代码在ubuntu kylin下编译不过，就因为返回引用。

二。接下来，我把<span style="font-family: Arial, Helvetica, sans-serif;">T_Counter<T>& operator +(const T_Counter<T>& t)改成如下：</span>

<span style="font-family: Arial, Helvetica, sans-serif;">T_Counter<T> operator +(const T_Counter<T>& t)</span>

<pre name="code" class="cpp"><pre name="code" class="cpp">
{T_Counter<T> temp;temp.a=a+t.a;return temp;
}

在两个系统下皆通过。

运行结果如下：

<img 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" alt="" />

我的理解：除了返回类型改成返回值，还有输入参数改为引用。查阅了一些资料，因为其实指针或地址都是在函数的栈上的，所以当函数返回时会销毁栈的东西，而值则是在堆上的，所以返回之后并没有问题。而输出结果少了第二行<span style="font-family: Arial, Helvetica, sans-serif;">T_Counter 20 destruct!是因为输入参数传入了引用t，所以并没有构造临时变量，也就没有析构。</span>

<span style="font-family: Arial, Helvetica, sans-serif;">
</span>

三。接下来，我把main函数里的c去掉。代码改成如下：

<pre name="code" class="cpp">        T_Counter<int> a(100),b(20);cout<<a+b<<endl;

问题：ubuntu下提示没有从T_Count<int>到T_Count<int>&的转换。看了一下，是重载+操作符函数的问题，因为

friend ostream& operator<<(ostream &output,T_Counter<T>& t)接收的是一个T_Count<int>&，而我们传入的是一个值。所以就出错了。

改成如下就没错，<span style="font-family: Arial, Helvetica, sans-serif;">friend ostream& operator<<(ostream &output,T_Counter<T> t)。但输出结果有点奇葩。</span>

<span style="font-family: Arial, Helvetica, sans-serif;">输出结果为：</span>

<img src="https://img-blog.csdn.net/20150405164744849?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvSW5jeV8xMjE4/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" style="font-family: Arial, Helvetica, sans-serif;" alt="" />

这里我就不理解啦。现在到VS下看看

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