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This program works fine if I work with numbers but not with strings

Bopaki (407)
If the variables are numbers I get the expected output
but if the variables are strings it bombs out.

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  #include<iostream>
#include<string>
using namespace std;

template<class Type>
Type swapTwoVariables(Type& var1, Type& var2);

int main()
{
    int var1; int var2;
    cin >> var1 >> var2;
    swapTwoVariables(var1, var2);
    cout << var1 <<" " << var2;
    //string var1;
    //string var2;
    //swapTwoVariables(var1, var2);
    //cout << var1 << " " << var2;
}
template<class Type>
Type swapTwoVariables(Type& var1, Type& var2)
{
    Type temp;
      temp = var1;
    var1 = var2;
    var2 = temp;
}

It works fine.
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#include<iostream>
#include<string>
using namespace std;

template<class Type>
Type swapTwoVariables(Type& var1, Type& var2);

int main()
{
    //int var1; int var2;
    //cin >> var1 >> var2;
    //swapTwoVariables(var1, var2);
    //cout << var1 <<" " << var2;
    string var1;
    string var2;
    swapTwoVariables(var1, var2);
    cout << var1 << " " << var2;
}
template<class Type>
Type swapTwoVariables(Type& var1, Type& var2)
{
    Type temp;
      temp = var1;
    var1 = var2;
    var2 = temp;
}


It bombs out and I get a blank screen:


Process returned 255 (0xFF) execution time : 10.397 s
Press any key to continue.

please help
JLBorges (13770)
The program engenders undefined behaviour.

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template<class Type>
Type swapTwoVariables(Type& var1, Type& var2)
{
    Type temp;
      temp = var1;
    var1 = var2;
    var2 = temp;

    // *** warning: no return statement in function returning non-void (GNU)
    // *** warning: control reaches end of non-void function (LLVM)
    // *** error: 'swapTwoVariables<...>': must return a value (Microsoft)
}

http://coliru.stacked-crooked.com/a/480a0f09d4cc5246
https://rextester.com/CGDPB51654
Bopaki (407)
Okay it now works fine.
I changed the template type to void and every thing now works fine

Thanks JLBorges
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