C equivalent of Java static block (Run once at startup)

Question

I have found plenty of answers to this question in C++, but I am strictly interested in C.

I have a circular linked list in C, and I want to initialize it with a dummy header node before the first time it is accessed. The dummy header node is a statically allocated global variable. This is my current solution:

static once = 1;
if(once){
    once = 0;
    // Setup code
}

This works, but I have to put it in every function that uses this linked list. (Of course, I can put this code in its own function, so I only have to call that function in every other function, but this isn't much better) Is there a better way? For example, if I have the following struct:

struct node {
    int value;
    struct node *next;
}

Is there any way to initialize one of these structs as a literal, such that its next value points to itself?

By "Initialize as a literal", I mean this: (Excuse my probably incorrect terminology)

struct test {
    int i;
    double d;
};

struct test magic = {1, 2.3}; // This can just be done at the top of the c file, outside of any functions

int someFunction(){...}

Answer 1

You can just do exactly what you say, and make it point to itself, if it's a file-scope variable:

#include <stdio.h>

struct node {
    int value;
    struct node * next;
};

struct node mylist = { 1, &mylist };

int main(void)
{
    printf("%d %d\n", mylist.value, mylist.next->value);
    return 0;
}

with output:

paul@horus:~/src/sandbox$ ./list
1 1
paul@horus:~/src/sandbox$ 

You can also, of course, add "run once at startup" code in main() before you do anything else, and achieve the same end:

#include <stdio.h>
#include <stdlib.h>

struct node {
    int value;
    struct node * next;
};

struct node * mylist;

int main(void)
{
    mylist = malloc(sizeof *mylist);
    if ( !mylist ) {
        perror("couldn't allocate memory");
        return EXIT_FAILURE;
    }

    mylist->value = 1;
    mylist->next = mylist;

    /*  Rest of your program here  */

    return 0;
}