C/C++ "suggest parentheses around comparison in operand of "错误

详细错误记录:

./dualview.c:57: error: two or more data types in declaration specifiers
./dualview.c:87: error: conflicting types for ‘show_settings’
./dualview.c:57: error: previous declaration of ‘show_settings’ was here
./dualview.c: In function ‘show_settings1’:
./dualview.c:104: warning: suggest parentheses around comparison in operand of &
./dualview.c:106: warning: suggest parentheses around comparison in operand of &
代码如下:

/* dualview.c -- 位字段和位运算 */
#include <stdio.h>
/* 位字段常量 */
/* 是否透明和是否可见 */
#define YES 1
#define NO 0
/* 边框线的样式 */
#define SOLID 0
#define DOTTED 1
#define DASHED 2
/* 三原色 */
#define BLUE 4
#define GREEN 2
#define RED 1
/* 混合颜色 */
#define BLACK 0
#define YELLOW (RED | GREEN)
#define MAGENTA (RED | BLUE)
#define CYAN (GREEN | BLUE)
#define WHITE (RED | GREEN | BLUE)

/* 位运算中使用的常量 */
#define OPAQUE 0x1
#define FILL_BLUE 0x8
#define FILL_GREEN 0x4
#define FILL_RED 0x2
#define FILL_MASK 0xE
#define BORDER 0x100
#define BORDER_BLUE 0x800
#define BORDER_GREEN 0x400
#define BORDER_RED 0x200
#define BORDER_MASK 0xE00
#define B_SOLID 0
#define B_DOTTED 0x1000
#define B_DASHED 0x2000
#define STYLE_NASK 0x3000

const char * colors[8] = {"black","red","green","blue","magenta","cyan","white"};
struct box_props
{
	unsigned int opaque 		:1;
	unsigned int fill_color 	:3;
	unsigned int 				:4;
	unsigned int show_border 	:1;
	unsigned int border_color 	:3;
	unsigned int border_style 	:2;
	unsigned int 				:2;
};


union Views/* 把数据看做结构或者unsigned short 变量 */
{
	struct box_props st_view;
	unsigned int ui_view;
}

void show_settings(const struct box_props *pb);
void show_settings1(unsigned short);
char *itobs(int n, char *ps);/* 把short值以二进制字符串的形式显示 */

int main(void)
{
	/* 创建 Views对象,初始化结构box view */
	union Views box = {{YES, YELLOW, YES, GREEN, DASHED}};
	char bin_str[8 * sizeof(unsigned int) + 1];

	printf("Original box settings:\n");
	show_settings(&box.st_view);
	printf("\nBox settings using unsigned int view:\n");
	show_settings1(box.ui_view);

	printf("bits are %s\n", itobs(box.ui_view,bin_str));
	box.ui_view &= ~FILL_MASK;/* 把代表填充色的位清0 */
	box.ui_view |= (FILL_BLUE | FILL_GREEN);/* 重置填充色 */
	box.ui_view ^= OPAQUE;/* 转置指示是否透明的位 */
	box.ui_view |= BORDER_RED;/* 错误的方法 */
	box.ui_view &= ~STYLE_NASK;/* 清楚样式位 */
	box.ui_view |= B_DOTTED;/* 把样式设置为点 */
	show_settings(&box.st_view);
	printf("\nBox settings using unsigned int view:\n");
	show_settings1(box.ui_view);
	printf("bits are %s\n", itobs(box.ui_view,bin_str));
	return 0;
}

void show_settings(const struct box_props *pb)
{
	printf("Box is %s\n", pb->opaque == YES ? "opaque" : "transparent");
	printf("The fill color is %s.\n", colors[pb->fill_color]);
	printf("Border %s.\n", pb->show_border == YES ? "shown" : "not shown");
	printf("The border color is %s\n", colors[pb->border_color]);
	printf("The border style is ");
	switch(pb->border_style)
	{
		case SOLID:printf("solid. \n");break;
		case DOTTED:printf("dotted.\n");break;
		case DASHED:printf("dashed.\n");break;
		default:printf("unknown type.\n");
	}
}

void show_settings1(unsigned short us)
{
	printf("box is %s.\n", us & OPAQUE == OPAQUE ? "opaque" : "transparent");
	printf("The fill color is %s\n", colors[(us >> 1) & 07]);
	printf("Border %s.\n", us & BORDER == BORDER ? "shown" : "not shown");
	printf("The border style is \n");
	switch(us & STYLE_NASK)
	{
		case B_SOLID : printf("solid.\n");break;
		case B_DOTTED : printf("dotted.\n");break;
		case B_DASHED : printf("dashed.\n");break;
		default:printf("unknown type.\n");
	}
	printf("The border color is %s.\n", colors[(us >> 9) & 07]);
}

/* 把int转换为二进制字符串 */
char *itobs(int n, char *ps)
{
	int i;
	static int size = 8 * sizeof(unsigned int);
	for (i = size -1; i >= 0; i--,n >>= 1)
	{
		ps[i] = (01 & n) + '0';
	}
	ps[size] = '\0';
	return ps;
}

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