代码易错的例子

示例1：

#include "stdio.h"
void main()
{
	int i = 1;
	if(0 != i);
	{
		printf("i的取值不为0");
		/* if条件满足时处理流程*/
	}
}

示例2：

#include "stdio.h"
typedef struct trqcUeInst
{
	int ueidx;
	int mcs;
	int transmode;
}TrqcUeInst;

void main()
{
	TrqcUeInst * ptrqcUeInst = NULL;
	TrqcUeInst tUeInst;
	//ptrqcUeInst = &tUeInst;
	printf("%d",ptrqcUeInst->ueidx);
}

示例3：

#include "stdio.h"
void main()
{
	unsigned int x = 0xffffffff;
	unsigned int result1 = 0;
	unsigned int result2 = 0;
	unsigned int result3 = 0;
	printf("%u\n",x);

	x = 0xefffffff;
	printf("%u\n",x);

	result1 = (x * 100) >> 9;
	result2 = (unsigned int)(((unsigned long long)(x * 100)) >> 9)//这种方式强转是错误的，因为是先乘100后已经溢出，再转为64位已失效。
	result3 = (unsigned int)(((unsigned long long)x * 100) >> 9);
	printf("%u\n",result1);
	printf("%u\n",result2);
	printf("%u\n",result3);	
}

示例4：

# include 
int main(void)
{
    int i = 1;
    switch(i)
    {
        case 1:
            printf("%d",i);
        case 2:
            printf("%d",i+1);
        case 3:
            printf("%d",i+2);
            break;
        default:
            printf("%d",i+10);
            break;
    }
}

上面程序i=1，第一个case条件满足，执行结果会输出：123

但如果每个case都加上break：

# include 
int main(void)
{
    int i = 1;
 
    switch(i)
    {
        case 1:
            printf("%d",i);
            break;
        case 2:
            printf("%d",i+1);
            break;
        case 3:
            printf("%d",i+2);
            break;
        default:
            printf("%d",i+10);
            break;
    }
}

执行结果只会输出：1