Be careful when you have to handle \0 character

I need to write some code to determine if a character belongs to a custom set. The code is as below:

bool isInMyCharSet(char ch)

{

  const char* myCharSet="ABCD12349";

  return strchr(myCharSet, ch)!=NULL?

}

The code works for years. Only one day you call this function with '\0'. Char 0 is not part of myCharSet, yet this function returns true.

Senior C programmers often know this, because this behavior is documented.

const char * strchr ( const char * str, int character );

      char * strchr (       char * str, int character );



Locate first occurrence of character in string

Returns a pointer to the first occurrence of character in the C string str.



The terminating null-character is considered part of the C string. Therefore, it can also be located to retrieve a pointer to the end of a string.

OK. Fine, but do you know the same behavior exists in CString::Find method. This time, you won't find it mentioned in the document.

Now you may attempt to change the code to

for(int i=0; i   if (myCharSet[i]==ch) return true;

}

return false;

Wrong again. sizeof operator still counts the terminating NUL character.