C++ Core Guidelines for static member variables

Question

I have a private static vector in my class that keeps a pointer to all objects created from it. It's necessary as each object needs access to information from all the other objects to perform some calculations:

// Header file:
class Example {
public:
    Example();
private:
    static std::vector<const Example*> examples_;
};
// Cpp file:
std::vector<const Example *> Example::examples_ = {};
Example::Example() {
    // intialization
    examples_.emplace_back(this);
}
void Example::DoCalc() {
    for (auto example : examples_) {
        // do stuff
    }
}

clang-tidy points out that I'm violating C++ Core Guidelines, namely : "Variable 'examples_' is non-const and globally accessible, consider making it const (cppcoreguidelines-avoid-non-const-global-variables)".

Personally, I don't see the resemblance between my code and the sample code in the core guidelines, especially since the variable is inside a class and private. What would be the 'correct' way of implementing this functionality? I don't want to disable this check from clang-tidy if it can be avoided.

Answer 1

What you've done is fine. This is literally the purpose of class-static. Some people would recommend alternatives, for unrelated reasons, which may be worth considering… but not because of anything clang-tidy is telling you here.

You've run into clang-tidy bug #48040. You can see this because it's wrong in its messaging: the vector is not "globally accessible", at least not in the sense of access rules, since it's marked private (though it's globally present across translation units, which is fine).

Your code doesn't relate to the cited core guideline.