bitreverse-1.c

来自「Mac OS X 10.4.9 for x86 Source Code gcc」· C语言 代码 · 共 98 行

/* APPLE LOCAL file */
#include <stdio.h>
#include <string.h>

/* This is the same data structure originally supplied by a user. */
/* { dg-do run { target powerpc*-*-darwin* } } */

/*
	Fun with bitfields!

	This needs to generate the same output when compiled with CodeWarrior and
	with XCode. Following is the output I see.

	CodeWarrior:

	u1: 0x0000808b
	u2: 0x51010001 0x00004045


	XCode:

	u1: 0xa2020002
	u2: 0x00010116 0x44040004
*/


#pragma reverse_bitfields on
#pragma ms_struct on

typedef struct
{
	union
		{
		unsigned int i1;
		struct
			{
			unsigned int b1: 1;
			unsigned int b2: 2;
			unsigned int b3: 4;
			unsigned int b4: 8;
			unsigned int b5: 16;
			} bits;
		} u1;

	union
		{
		struct
			{
			unsigned int i2;
			unsigned int i3;
			} ints;

		struct
			{
			unsigned int b1: 16;
			unsigned int b2: 8;
			unsigned int b3: 4;
			unsigned int b4: 2;
			unsigned int b5: 1;
			unsigned int b6: 2;
			unsigned int b7: 4;
			unsigned int b8: 8;
			unsigned int b9: 16;
			} bits;
		} u2;
} Bitfields;


int main()
{
	Bitfields bitfields;


	memset(&bitfields, 0, sizeof(bitfields));

	bitfields.u1.bits.b1 = 1;
	bitfields.u1.bits.b2 = 1;
	bitfields.u1.bits.b3 = 1;
	bitfields.u1.bits.b4 = 1;
	bitfields.u1.bits.b5 = 1;

	bitfields.u2.bits.b1 = 1;
	bitfields.u2.bits.b2 = 1;
	bitfields.u2.bits.b3 = 1;
	bitfields.u2.bits.b4 = 1;
	bitfields.u2.bits.b5 = 1;
	bitfields.u2.bits.b6 = 1;
	bitfields.u2.bits.b7 = 1;
	bitfields.u2.bits.b8 = 1;
	bitfields.u2.bits.b9 = 1;

	if (bitfields.u1.i1 != 0x0000808b ||
	    bitfields.u2.ints.i2 != 0x51010001 ||
	    bitfields.u2.ints.i3 != 0x00004045)
	  return 42;
    return 0;
}