/* * dataalign.c -- show alignment needs * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files.  The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates.   No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * This runs with any Linux kernel (not any Unix, because of <linux/types.h>) */#include <stdio.h>#include <sys/utsname.h>#include <linux/types.h>/* * Define several data structures, all of them start with a lone char * in order to present an unaligned offset for the next field */struct c   {char c;  char      t;} c;struct s   {char c;  short     t;} s;struct i   {char c;  int       t;} i;struct l   {char c;  long      t;} l;struct ll  {char c;  long long t;} ll;struct p   {char c;  void *    t;} p;struct u1b {char c;  __u8      t;} u1b;struct u2b {char c;  __u16     t;} u2b;struct u4b {char c;  __u32     t;} u4b;struct u8b {char c;  __u64     t;} u8b;int main(int argc, char **argv){    struct utsname name;    uname(&name); /* never fails :) */    printf("arch  Align:  char  short  int  long   ptr long-long "	   " u8 u16 u32 u64\n");    printf(       "%-12s  %3i   %3i   %3i   %3i   %3i   %3i      "	   "%3i %3i %3i %3i\n",	   name.machine,	   /* note that gcc can subtract void * values, but it's not ansi */	   (int)((void *)(&c.t)   - (void *)&c),	   (int)((void *)(&s.t)   - (void *)&s),	   (int)((void *)(&i.t)   - (void *)&i),	   (int)((void *)(&l.t)   - (void *)&l),	   (int)((void *)(&p.t)   - (void *)&p),	   (int)((void *)(&ll.t)  - (void *)&ll),	   (int)((void *)(&u1b.t) - (void *)&u1b),	   (int)((void *)(&u2b.t) - (void *)&u2b),	   (int)((void *)(&u4b.t) - (void *)&u4b),	   (int)((void *)(&u8b.t) - (void *)&u8b));    return 0;}