Implementing a string class in C++

I recently attended an interview for a C++ position in a very reputed bank.

The interviewer started off by asking me to implement a string class but only interested in constructor, copy-constructor, assignment operator and destructor.

Basically, he wanted to know how I would implement Rule of Three and nothing else.
He's not even interested in move operations. I doubt he knows about them. That's a different matter anyways.

So, I implemented the assignment operator in terms of copy constructor:

class String {   .... String& operator=(String other) {    std::swap(m_data, other.m_data);    return *this; }  private:    char* m_data; };    

Since this is pretty common way to implement assignment operator, I thought he would like it. The problem started with that.

He questioned why I implement it that way. When I explained that this is exception safe way of implementing it, he became very uncomfortable and asked what's wrong in implementing it:

String& operator=(const String& other) {    if (this != &other)    {      delete[] m_data;      m_data = new char[strlen(other.m_data) + 1] {'\0'};      strcpy(m_data, other.m_data);      return *this;    }  }    

His argument was:

We are about to overwrite the data anyways so what's wrong in deleting first even if it's not exception safe?

At that moment it did not occur to me that code will crash in the event of an exception but I did try to argue that internal data should retain original values in the event of an exception.
Needless to say, what was outcome of the interview as most of the time was lost in that argument itself.

Had he argued on the basis that copy-and-swap will always do reallocation even if there is enough size, etc, I would have felt happy. But his argument was that he wants performance at any cost.

I would like to know how one should act in such situations. Just give up, or feel better that you don't have to work with such a project/team lead?

Replay

Category: c# Time: 2016-07-28 Views: 0

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