Compile time check to validate structure size

BUILD_BUG_ON.c

#include <stdio.h>

#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2 * !!(condition)]))

int main(void)
{
    struct t { 
        int x;
        int y;
        int z;
    };  
    BUILD_BUG_ON(sizeof(struct t) < 10);    // This passes compilation
    BUILD_BUG_ON(sizeof(struct t) < 20);    // This fails compilation
    printf("ok\n");
    return 0;
}