Why the following code return error when variable is declared global.
int add(int x, int y) {
return x+y;
}
int ab = add(10, 20);
int main(void) {
printf("%d", ab);
}
But if I call like this:
int add(int x, int y) {
return x+y;
}
int main(void) {
int ab = add(10, 20); // Variable declare inside main
printf("%d", ab);
}
then it executes without an error.
Initializers for global variables must be constant, they can't be an arbitrary expression.
In C language you cannot execute code in the global scope, outside a function and store the return value of the function in a global variable.
Global variables must be constant at initialisation, and when you're doing :
x = func ( ... )
The return of the function is not constant.
From section 3.5.7 Initialization of the C standard:
All the expressions in an initializer for an object that has static storage duration or in an initializer list for an object that has aggregate or union type shall be constant expressions.
and ab has static storage duration but add() is not a constant expression.
