Initializing a Global Struct in C

Question

What is the best way to accomplish the following in C?

#include <stdio.h>  struct A {     int x; };  struct A createA(int x) {     struct A a;     a.x = x;     return a; }  struct A a = createA(42);  int main(int argc, char** argv) {     printf("%d\n", a.x);     return 0; } 

When I try to compile the above code, the compiler reports the following error:

"initializer element is not constant"

The bad line is this one:

struct A a = createA(42); 

Can someone explain what is wrong? I'm not very experienced in C. Thanks!

Answer 1

struct A a = { .x = 42 }; 

More members:

struct Y {     int r;     int s;     int t; };  struct Y y = { .r = 1, .s = 2, .t = 3 }; 

You could also do

struct Y y = { 1, 2, 3 }; 

The same thing works for unions, and you don't have to include all of the members or even put them in the correct order.

Answer 2

Why not use static initialization?

struct A a = { 42 };