C++ move assignment operator

All for efficiency. C++11

#include <iostream>
#include <cstdint>
#include <cstring>
#include <memory>
class String
{
private:
  char *mData;
  uint32_t mSize;
public:
  // default constructor. 
  // could have used `String() = default`, but for printing.
  String()
  {
    printf("default constructor");
  }
  // constructor that are useful for this application
  String(const char *str)
  {
    printf("created: ");
    mSize = strlen(str);
    mData = new char[mSize];
    memcpy(mData, str, mSize);
    print();
  }
  // copy constructor
  String(const String &other)
  {
    printf("copied: ");
    mSize = other.mSize;
    mData = new char[mSize];
    memcpy(mData, other.mData, mSize);
    print();
  }
  // move constructor
  String(String &&other)
  {
    printf("moved: ");
    mSize = other.mSize;
    mData = other.mData;
    other.mSize = 0;
    other.mData = nullptr;
    print();
  }
  // move assignment operator
  String &operator=(String &&other)
  {
    printf("move assigned: ");
    if (this != &other)
    {
      // if missing this, mData of original will be dangling
      delete[] mData;    
      mSize = other.mSize;
      mData = other.mData;
      other.mSize = 0;
      other.mData = nullptr;
      print();
    }
    return *this;
  }
  ~String()
  {
    printf("destrying...");
    print();
    delete[] mData;
  }
int size()
  {
    return mSize;
  }
void print()
  {
    for (int i = 0; i < mSize; i++)
    {
      printf("%c", mData[i]);
    }
    printf("\n");
  }
};
int main()
{
  String src = "Hello";
  String desc(std::move(src)); // move constructor will be called
  String src2 = "World";
  String desc2(std::move(src2)); // move constructor will be called
  String src3 = "!";
  // move constructor will be called.
  // This is not assignment. This is a construction!!  
  String desc3 = std::move(src3);
  desc.print();
  desc2.print();
  desc3.print();
  // assignment happens only when you assign to an existing variable
  desc3 = std::move("Again!");
  desc3.print();
}