Page History

...

Because comparison functions (like strcmp) return 0 for equality and non-zero for inequality, they can cause confusion when used to test for equality. If someone were to switch the following strcmp call with an equals function, they might instinctively just replace the function name. Also, when quickly reviewed, the code could easily appear to test for inequality.

char *str1;
char *str2;

if (!strcmp(str1, str2)) {
  return "strings are equal"void login(char *usr, char *pw)
{
  User user = find_User(usr);
  if (!strcmp((user->password),pw_given)) {
    grantAccess();
  }
  denyAccess("Incorrect Password");
}

int check_password(char *usr, char *pw_given)
{
  User user = find_User(usr);
  if (!strcmp((user->password),pw_given)) {
    return 1;
  }
  return 0;
}

void login(char *usr, char *pw)
{
  if (!check_password(usr, pw)) {
    grantAccess();
  }
  denyAccess("Incorrect Password");
}

However, doing so would produce incorrect behavior. As a result, such a result should never be defaulted.

...

char *str1; 
char *str2;

if (strcmp(str1, str2) == 0) {
  return "strings are equal";
}

...

References

[1] "Should I return TRUE / FALSE values from a C function?"

...