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