Is "const int x = get();" legal in C?Can we assign a function's return value to a constant at declaration?

Question

A highly reputed contributor "R.." on this forum explicitly told me this 2 days back:

Initializers for objects of static storage duration must be constant expressions. The result of a function call is not a constant expression.

He was talking about global variables.But I am not sure what goes with constants declared inside the main() function, or any function for that matter.Though intuitively I feel it is so even for constants declared within functions,the following program sourced from the following link, with its supposedly correct answer, is confusing me.

http://www.indiabix.com/c-programming/const/discussion-546

#include<stdio.h>
int get();

int main()
{
    const int x = get();
    printf("%d", x);
    return 0;
}

int get()
{
    return 20;
}

So can anyone explain whether it's valid in C to assign a return value to a constant?

Answer 1

Yes, it's perfectly valid, since your variable is automatic, i.e. not static.

The restrictions apply to static variables, whose values must be known at compile-time.

Note that C differentiates between "constant expressions" and other expressions, and that the initializer value used for static variables must be such a constant expression. For non-static variables, there is no such requirement.