C++ segmentation error when first parameter is null in comparison operator overload

Question

I am writing a class called Word, that handles a c string and overloads the <, >, <=, >= operators.

word.h:

friend bool operator<(const Word &a, const Word &b);

word.cc:

bool operator<(const Word &a, const Word &b) {
  if(a == NULL && b == NULL)
    return false;

  if(a == NULL)
    return true;

  if(b == NULL)
    return false;

  return strcmp(a.wd, b.wd) < 0;  //wd is a valid c string, EDIT: changed to strcmp
}

main:

char* temp = NULL;     //EDIT: i was mistaken, temp is a char pointer
Word a("blah");    //a.wd = [b,l,a,h]
cout << (temp<a);

I get a segmentation error before the first line of the operator< method after the last line in the main. I can correct the problem by writing

cout << (a>temp);

where the operator> is similarly defined and I get no errors but my assignment requires (temp < a) to work so this is where I ask for help.

EDIT: I made a mistake the first time and i said temp was of type Word, but it is actually of type char*. So I assume that the compiler converts temp to a Word using one of my constructors. I dont know which one it would use and why this would work since the first parameter is not Word.

here is the constructor I think is being used to make the Word using temp:

Word::Word(char* c, char* delimeters="\n") {
  char *temporary = "\0";
  if(c == NULL)
    c = temporary;
  check(stoppers!=NULL, "(Word(char*,char*))NULL pointer"); // exits the program if the expression is false
  if(strlen(c) == 0)
    size = DEFAULT_SIZE;  //10
  else
    size = strlen(c) + 1 + DEFAULT_SIZE;
  wd = new char[size];
  check(wd!=NULL, "Word(char*,char*))heap overflow");
  delimiters = new char[strlen(stoppers) + 1];      // EDIT: changed to []
  check(delimiters!=NULL,"Word(char*,char*))heap overflow");
  strcpy(wd,c);
  strcpy(delimiters,stoppers);
  count = strlen(wd);
}

wd is of type char*

thanks for looking at this big question and trying to help. let me know if you need more code to look at

Answer 1

I'm almost positive you did not mean to construct a char on the heap with an initial value of some integer based on the size of stoppers:

delimiters = new char(strlen(stoppers) + 1); // Should use [] not ()

Also you are using C++ and I would never tell you what to do, but please, unless you know exactly that there is no danger, do not use strcpy. For exactly this reason.

It is a blind copy of strings, and when the destination does not have enough space (as is the case from your typo-ed allocation), things go BAD.

EDIT:

I also see in your overload of operator< that you use

a.wd < b.wd

and claim that .wds are valid C strings. If that is the case, you cannot apply a simple < operator to them and must use strcmp, strncmp or some other full compare function