Do all const objects have static storage duration?

Question

I wonder if all constants in C++ have static duration, even though they are created inside a function other than main()?

For example:

const int a = 3;     

int main()
{
    const int b = 4;
}

What is the difference between a and b?

Answer 1

Whether an object is const and whether it has static storage duration are unrelated. An object defined inside a function has automatic storage duration unless explicitly marked static or thread_local. A static data member of a class has static storage duration unless explicitly marked thread_local. An object defined at namespace scope has static storage duration unless explicitly marked thread_local.

Answer 2

No; this is clearest if you create a const object with a constructor and destructor, which will be called when the program enters and leaves the scope in which the automatic const object is declared. The const automatic variable can also have different values on each invocation of the function, based on the parameters or other runtime data, while a static const local variable could not.

A constexpr object, however, cannot have non-trivial constructor or destructor or be initialized to anything but constants known at compile time, so it could be implemented the same way as a static variable.