我可以在C ++标准中找到在全局范围内调用函数的支持吗？

Question

Consider the snippet below:

#include <iostream>
int f(int i) {
    return ++i;
}
int i = f(i);

int main() {
    std::cout << i << '\n';
}

Where in the C++ Standard can I find support for the initialization of the global variable i above?

Answer 1

Initialisation of non-local variables is described in the chapter titled "Initialization of non-local variables", [basic.start.init]. In C++11, that's 3.6.2.

Initialising using = , the initialiser can be a braced list, or any assignment expression, including a function call, as specified in [dcl.init] (C++11 8.5).

This has static storage duration, so it's first zero-initialised during static initialisation per 3.6.2/2:

Variables with static storage duration [...] shall be zero-initialized before any other initialization takes place.

It is then initialised from its initialiser during dynamic initialisation, since it doesn't meet the criteria for constant initialisation (since the initialiser isn't a constant expression). That passes the statically initialised zero value to the function, which increments it and returns 1. That value of 1 is used to complete the initialisation.