这个代码怎么错了？C++

#include <iostream>
using namespace std;

char * GetSubstr(char *sub, char *str)
{
//...请补充完整
}

int main()
{
char *substr;
substr=GetSubstr("two","One two three four five");
cout<<"找到的子串为："<<substr<<endl;
return 0;
}
运行是死掉~~~
是下面这个。怎么错了？？可以编译不能运行…………

#include <iostream>
using namespace std;

char * GetSubstr(char *sub, char *str)
{
int i=0,csub=0,cstr=0,x=0;
while(*(sub+i)!='\0')
{
csub++;
i++;
}
i=0;
while(*(str+i)!='\0')
{
cstr++;
i++;
}

for(i=0;i<cstr;i++)
{int j;
if(*(sub)==*(str+i))
{
for(j=0;j<csub;j++)
{x=0;
if(*(sub+j)!=*(str+i+j))
{break;}
else
{x++;}
}
if(x==csub)
{return str+i;break;}