Question

If I have a static local variable within a static global function (not class static, global static)…

foo.cpp:

static void f()
{
    static T x;
    ...
}

Is the x instance guaranteed to be singleton across the application?

What if two translation units defined static void f() as above. Would they each have their own x instance, or would they share? Why?

Answer 1

static functions have internal linkage, so each f in each translation unit would be a different independent function, and there would be an instance of x per translation unit.