Overload Operator = breaks std :: sort

Question

Probably a hoax, but I can't find it.

After two days of nunchucking my keyboard, I found that overloading the equals ( operator=) operator seems to break std::sort. Maybe I'm overloading operator=wrong? This is my MCVE:

#include <algorithm>
#include <functional>
#include <iostream>
#include <string>
#include <cstdint>
#include <vector>

struct Person
{
  std::string name;
  uint32_t age;

  bool operator< (const Person& p)
  {
    return this->age < p.age;
  }

  Person operator= (const Person& p)
  {
    Person newP;
    newP.name = p.name;
    newP.age = p.age;

    return newP;
  }

  static bool SortPeople(const Person& p1, const Person& p2)
  {
    return p1.age < p2.age;
  }
};

void PrintPeople(const std::vector<Person>& people)
{
  std::cout << "============ people begin" << std::endl;
  for (const auto& pIt : people)
  {
    std::cout << "name: " << pIt.name << ", age: " << pIt.age << std::endl;
  }
  std::cout << "============ people end" << std::endl;
}

int main()
{
  std::vector<Person> people = { { "james", 12 },
                                 { "jada", 4   },
                                 { "max", 44   },
                                 { "bart", 7   }
                               };

  PrintPeople(people);


  std::sort(people.begin(), people.end());
  PrintPeople(people);  

  return 0;
}

If I run this code as is, each person is not sorted by age. PrintPeopleis output in the same order that I initialized peoplein. However, if I comment on the entire function Person operator=, then it peopleprints in ascending order of age. I see the same behavior, whether I call std::sort(people.begin(), people.end());or std::sort(people.begin(), people.end(), Person::SortPeople);, and I see the same behavior, whether I use g++version 7.2.1 or clang++version 4.0.1. I am running Fedora 27.

- , operator= std::sort?

-Wall -Wextra -Wconversion -std=c++11, .

Answer 1

, operator=. *this, newP.

Person& operator= (const Person& p)
{
  name = p.name;
  age = p.age;

  return *this;
}

std::sort , , operator= Person. std::sort .

BTW: , .

Answer 2

operator= : ( *this, ), *this .