type-punning ans strict aliasing

type-punning

#include <stdio.h>
#include <stdlib.h>
 
/**
 * gcc -O2 will cause `tail = (Node*)&list;` to be optimized out, will give list === null
 */
typedef struct Node_ {
    struct Node_* next;
    int val;
} Node;
 
int main(int argc, char *argv[])
{
    Node *list, *tail, *n;
 
    list = NULL;
    tail = (Node*)&list;
 
    for (int i = 0; i < 10; i++) {
        n = (Node*)malloc(sizeof(Node));
        n->val = i;
        n->next = NULL;
 
        tail->next = n;
        tail = n;
    }
 
    if (list == NULL) {
        printf("list is null?\n");
    } else {
        printf("list: ");
        n = list;
        while (n) {
            printf("%d ", n->val);
            n = n->next;
        }
        putchar('\n');
    }
 
    return 0;
}