1.myStrnpy(str,p,9);  //把p地址的前9位字符串拷贝到str这边来

#include <stdio.h>char* myStrcpy(char *des,char *src)  //目标地址，原地址
{if(des == NULL || src == NULL){return NULL;}char *bak = des;  //目标地址赋值给备份地址while(*src !='\0'){*des = *src;des++;src++;}*des = '\0';return bak;
}char* myStrcpy2(char *des,char *src)  //目标地址，原地址
{if(des == NULL || src == NULL){return NULL;}char *bak = des;  //目标地址赋值给备份地址while(*src !='\0'){*des++ = *src++;}*des = '\0';return bak;
}char* myStrcpy3(char *des,char *src)  //目标地址，原地址
{if(des == NULL || src == NULL){return NULL;}char *bak = des;  //目标地址赋值给备份地址while( (*des++ = *src++)!='\0'){   //赋值归赋值，是可以多一层判断的//赋值加判断 可以一起  }*des = '\0';return bak;
}char* myStrnpy(char *des,char *src,int count)  //目标地址，原地址
{if(des == NULL || src == NULL)  //判断目的地址和原地址不等于0{return NULL;}char *bak = des;  //目标地址赋值给备份地址while(*src !='\0' && count>0){*des++ = *src++;count--;*des = '\0';}if(count >0)   {while(count > 0){count--;*des++ = '\0';  //给多出来的位置赋值}}*des = '\0';return bak;
}int main()
{char str[128] = {'\0'};char *p = "caoshupei handsome";myStrcpy(str,p);  //把p拷贝到str这边来puts(str);myStrcpy2(str,p);puts(str);myStrcpy3(str,p);puts(str);myStrnpy(str,p,9);puts(str);return 0;
}

2. 断言：assert ( ) 判断括号内其值为假（为0）则终止程序

#include "assert.h"

void assert(int experssion);

输出expression：在哪里错误

#include <stdio.h>
#include "assert.h"char* myStrcpy(char *des,char *src)  //目标地址，原地址
{assert(des!= NULL && src != NULL);char *bak = des;  //目标地址赋值给备份地址while(*src !='\0'){*des = *src;des++;src++;}*des = '\0';return bak;
}char* myStrcpy2(char *des,char *src)  //目标地址，原地址
{if(des == NULL || src == NULL){return NULL;}char *bak = des;  //目标地址赋值给备份地址while(*src !='\0'){*des++ = *src++;}*des = '\0';return bak;
}char* myStrcpy3(char *des,char *src)  //目标地址，原地址
{if(des == NULL || src == NULL){return NULL;}char *bak = des;  //目标地址赋值给备份地址while( (*des++ = *src++)!='\0'){   //赋值归赋值，是可以多一层判断的//赋值加判断 可以一起  }*des = '\0';return bak;
}char* myStrnpy(char *des,char *src,int count)  //目标地址，原地址
{if(des == NULL || src == NULL)  //判断目的地址和原地址不等于0{return NULL;}char *bak = des;  //目标地址赋值给备份地址while(*src !='\0' && count>0){*des++ = *src++;count--;*des = '\0';}if(count >0)   {while(count > 0){count--;*des++ = '\0';  //给多出来的位置赋值}}*des = '\0';return bak;
}int main()
{char str[128] = {'\0'};char *p = "caoshupei handsome";char *pstr = NULL;myStrcpy(pstr,p);  //把p拷贝到str这边来myStrcpy(str,p);  //把p拷贝到str这边来puts(str);myStrcpy2(str,p);puts(str);myStrcpy3(str,p);puts(str);myStrnpy(str,p,9);puts(str);return 0;
}