Thread: Question related to NULL assignment in pointers to structs

Originally Posted by Sir Galahad

Side note: the two words actually come from the same root. To be a "good man" for example used to mean a "godly man". Of course the meanings have obviously diverged quite a bit over the millennia. (As in, "He was a good thief"!)

Back to the topic, I almost always initialize variables (global or otherwise) regardless. For me it is simply a matter of style, really, even though the standard does basically guarantee that globals will zero-initialized. That said, there are some instances where I do indeed omit the initialization:

Code:

int ch;
for (;;) {
  ch = getchar();
  if(ch == EOF)
    break;
  // do something with 'ch' 
}

I think the fact the declaration is "within view" of where it is being used is why I don't have any issues with that. As long as it is obvious that the variable in question is "decidedly uninitialized", why not?

Yes, in this very simple example, the initialization is not needed. But in real life and actual programs, it might be too easy for the author, or maintainer when adding or changing code, to use an uninitialized variable, assuming the variable has a valid value.

If all programmers, especially beginning programmers, initialize ALL variable definitions, both global and especially local variables, then possible errors are greatly reduced!

When you identify a pointer as NULL, this means there's no instantiation of a struct of the type node that you have just defined associated with it yet. There is no struct of the type node in memory that it points to.

You can attach a struct of the type node to the pointer, for instance:

Code:

struct node
{
  int value;
  struct node *next;
};

node* first;
node myIntEnum;
myIntEnum.value = 20;
first = &myIntEnum;

But until you do so, there is no pointer to the next element in the enumeration. Once you have your first element of the enumeration - say "node firstNode;" - when you don't have your second yet, the value of firstNode.next will be NULL.

Once you have defined your type "node" as a "struct," I don't think you have to keep repeating that a node is a struct in declaring variables of the type node. You have to look this up to be sure, but once you have defined the type "node" you should just be able to call it just a node.

Also look into type definitions in C in terms of defining your own types.