下面是介绍这个函数给出的例子，好像有问题哦

函数名: memchr
功  能: 在数组的前n个字节中搜索字符
用  法: void *memchr(void *s, char ch, unsigned n);
程序例:

#include <string.h>
#include <stdio.h>

int main(void)
{
   char str[17];
   char *ptr;

   strcpy(str, "This is a string");
   ptr = memchr(str, 'r', strlen(str));
   if (ptr)
      printf("The character 'r' is at position: %d\n", ptr - str);
   else
      printf("The character was not found\n");
   return 0;
}

没啥问题

ptr = memchr(str, 'r', strlen(str));

error C2440: '=' : cannot convert from 'void *' to 'char *'

算你的编译器有脾气
在等号后面加上(char *)转换一下类型来迁就它好了