g++11 for unordered_map is not compatible with versions earlier than gcc-11

Question

Introduction

I recently upgraded the gcc version of a project from 7.5 to 11.4. After the upgrade, I found some exceptions at runtime. After tracing, it was found that an exception occurred when calling a class member function of a library compiled by gcc-7.5. This class has a private member of type unordered_map, it's constructor will insert some values into unordered_map, while in the function, will take some values from it. The logic is simple, but you will find that the keys in unordered_map are all incorrect

Recurrent

You can use the following sample in ubuntu1804 to reproduce the problem

// kernel.h
#include <memory>
#include <string>
#include <unordered_map>

struct Kernel {
  Kernel();

  void Print();

 private:
  std::unordered_map<int, std::shared_ptr<int>> mapping_;
};


// kernel.cc
#include <iostream>
#include "kernel.h"

Kernel::Kernel() { 
        mapping_[5] = std::make_shared<int>(233); 
        mapping_[6] = std::make_shared<int>(234);
        mapping_[7] = std::make_shared<int>(235);
        mapping_[8] = std::make_shared<int>(236);
}

void Kernel::Print() {
  for (auto &[key, value] : mapping_) {
    std::cout << key << " " << value << " " << *value << std::endl;
  }
}


//test.cpp

#include "kernel.h"

int main() {
  Kernel kernel;
  kernel.Print();

  return 0;
}

Compile Command

g++ kernel.cc -o kernel.o -c --std=c++17
g++-11 test.cpp kernel.o -o test --std=c++17

Execute Command

./test

You will get similar results as follows

enter image description here

Tip

1. After testing, it has been found that any combination of g++-7 ~ g++-10 is acceptable. However, if you use a version of g++7 ~ g++10 to compile kernel.o, and use g++-11 ~ g++-13 to compile test.cpp, the problem will recur.
2. If you move the position of the kernel.o parameter before test.cpp, the result will be normal again

g++ kernel.cc -o kernel.o -c --std=c++17
g++-11 -o test kernel.o test.cpp --std=c++17