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 <stdio.h> 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 <stdio.h> 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