C++程序崩溃

Question

我有这个任务来实现 strcmp 函数。有时它运行正常，但有时它会崩溃。请帮助我。

#include <iostream>

using namespace std;     

int mystrcmp(const char *s1, const char *s2);

int main()
{
cout<<mystrcmp("A","A")<<endl;     
cout<<mystrcmp("B","A")<<endl;     
cout<<mystrcmp("A","B")<<endl;     
cout<<mystrcmp("AB","A")<<endl;

return 0;     
}

int mystrcmp(const char *s1, const char *s2)
{
 while (*s1==*s2)
 {
  s1++;
  s2++;
 }

 if(*s1=='\0')
  return(0);

 return(*s1-*s2);
}

Answer 1

如果两个输入相同，它将崩溃，因为您的循环继续超出终止 nul 字符。

要解决此问题，您必须检查 nul 字符 inside 循环如下:

while (*s1==*s2) {

  // if s1 points to nul character, then s2 should also, because of the ==
  // which means we've reached the end of the strings and they are equal
  // so return 0.
  if(*s1=='\0')
    return 0;

  s1++;
  s2++;
 }

 return *s1-*s2;