inline variable is initialized more than once

Question

Im seeing some examples of inline const variable getting initialized (and destructed) 3 times with visual studio 2017. Is this is a bug with the linker ? or is

Answer 1

This appears to be an MSVC bug. I'm able to reproduce it with the code below (also with VS2017 15.8.9). Interestingly, I can only reproduce with a Debug build. In Release mode, the optimizer seems to save us.

Common.h

#pragma once

#include 

class Foo
{
public:
  Foo()
  {
    std::cout << "Constructing a Foo" << std::endl;
  }

  ~Foo()
  {
    std::cout << "Destructing a Foo" << std::endl;
  }
};

inline Foo const Bar;

other.cpp

#include "common.h"

void DoOtherStuff()
{
  std::cout << &Bar << std::endl;
}

main.cpp

#include "common.h"

void DoStuff()
{
  std::cout << &Bar << std::endl;
}

extern void DoOtherStuff();

int main()
{
  DoStuff();
  DoOtherStuff();
}

Output (Debug)

Constructing a Foo
Constructing a Foo
00007FF74FD50170
00007FF74FD50170
Destructing a Foo
Destructing a Foo