bsearch（）函数里的最后一个形参是指向函数的指针啊，直接传入CMP为什么没有用？

Question

#include <stdio.h>#include <stdlib.h>int CMP(int *a,int *b){if(*a<*b)return -1;else if(*a>*b)return 1;elsereturn 0;}int main(void){int search[10]={1,3,6,7,10,11,13,19,28,56} ;int a=13,*p,i;/*对数组search 进行二分搜索13*/p=(int *)bsearch(&a, search,10, sizeof(int),(int(*)(const void *,const void *))CMP);printf("The elems of the array are\n");for(i=0;i<10;i++)printf("%d ",search[i]);/*显示元素13 在原数组中的位置*/if(p)printf("\nThe elem 13 is located at %d of the array\n",p-search+1);elseprintf("\nSearch is fail!!\n");getchar();}p=(int *)bsearch(&a, search,10, sizeof(int),(int(*)(const void *,const void *))CMP);在CMP函数前为什么还要加强制类型转换？

Answer 1

你试运行一下这个代码：

#include <stdio.h>#include <stdlib.h>/*_CRTIMP __checkReturn void * __cdecl bsearch(__in const void * _Key, __in_bcount(_NumOfElements * _SizeOfElements) const void * _Base,        __in size_t _NumOfElements, __in size_t _SizeOfElements,        __in int (__cdecl * _PtFuncCompare)(const void *, const void *));*/int CMP(int *a,int *b){    int tmp = 0;    if(*a<*b)        tmp = -1;    else if(*a>*b)        tmp = 1;    else        tmp = 0;    printf("tmp = %d\n", tmp);    return tmp;}int main(void){    int search[10]={1,3,6,7,10,11,13,19,28,56} ;    int a=3,*p,i;    /* 对数组search 进行二分搜索a */    p=(int *)bsearch(&a, search, 10, sizeof(int),(int(*)(const void *,constvoid *))CMP);    printf("The elems of the array are\n");    for(i=0;i<10;i++)        printf("%d ",search[i]);    /*显示元素a 在原数组中的位置*/    if(p)        printf("\nThe elem %d is located at %d of the array\n",a, p-search+1);    else        printf("\nSearch is fail!!\n");    getchar();}

tmp = -1tmp = 0The elems of the array are1 3 6 7 10 11 13 19 28 56The elem 3 is located at 2 of the array

我在注释里面给你贴出来了bsearch的函数原形阿，你能看得出来的，类型mismatch的话肯定编译都会失败的阿