整型溢出问题

整型溢出问题是常见问题，通过下面的例子去品味整型溢出的“乐趣”吧。

#include <stdio.h>/*对于unsigned整型溢出，C的规范是有定义的——“溢出后的数会以2^(8*sizeof(type))作模运算”，也就是说，如果一个gned char（1字符，8bits）溢出了，会把溢出的值与256求模。对于signed整型的溢出，C的规范定义是“undefined behavior”，也就是说，编译器爱怎么实现就怎么实现。*/void test_IntegerOverflow(){        unsigned char ch = 0xff;        signed char sch = 0x7f, mul = 0x05;        printf("unsigned char ch %d\n", ++ch);        printf("signed char sch * mul %d\n", (signed char)(sch*mul) );        printf("signed char sch %d\n",++sch);}int main(){        test_IntegerOverflow();        return 0;}

 

运行结果

unsigned char ch 0
signed char sch * mul 123
signed char sch -128