在 C++ 中，哪些链接被授予非局部成员变量？

Question

I assume that a class's data members have linkage(or no linkage) like below
Is that correct?

class AAA {
public:                          // this doesn't matter

  int var1;                      // no linkage
  const int var2 = 0;            // no linkage

  static int var3;               // external linkage (declaration)
  static const int var4 = 0;     // external linkage (declaration + definition)

};

int AAA::var3 = 0; // external linkage (definition)

Answer 1

First of all I questioned about which linkages are granted to data members
and my assumption was right and MM answered it's OK too
I double checked in the standard and yes, linkages are correct like I and MM said above

But as MM mentioned I misunderstood which one is declaration or definition
It's a bit out of topic but I answer it by myself for someone who read this in future

[1] if it comes to non-static data member

struct A {
  int var1;        // definition (initial value is 0)
  int var2 = 100;  // definition (initial value is 100)
};

[2] if it comes to static const

struct A {
  static const int var1 = 100; // declaration (initial value is 100)
  static const int var2;       // declaration (initial value is 0)
};

const int A::var1;             // definition (an option for odr-used situation)
const int A::var2 = 10;        // definition

[3] if it comes to static constexpr

constexpr data members are interesting and work differently
because from C++17 a data member with constexpr implies inline
and inline actually define it

plus every inline data members in every translation units are guaranteed to have same only one definition
( https://eel.is/c++draft/depr.static.constexpr )

struct A {
  static constexpr int n = 5;   // definition (declaration in C++ 2014)
};

constexpr int A::n;             // redundant declaration (definition in C++ 2014)

for example if I have 2 translation units like below

// foo.cpp
#include <iostream>

class AAA {
public:
    static constexpr int var = 10; 
};

void foo() {
    std::cout << &AAA::var << std::endl;
}

// main.cpp
#include <iostream>

class AAA {
public:
    static constexpr int var = 10; 
};

void foo();

int main() {
    std::cout << &AAA::var << std::endl;
    foo();
}

and result is like below

$ g++ -std=c++17 main.cpp foo.cpp
$ ./a.out 
0x564ba82a3a54
0x564ba82a3a54