How to access a struct from a class?

Question

I was reading a block of codes from a C++ book, and trying to compile it using g++

Here was the error: main.cpp:11:3: error: 'link' does not name a type main.cpp: In constructor 'linklist::linklist()': main.cpp:15:4: error: 'first' was not declared in this scope

So it seems like the linklist class doesnt recognize the link struct, why?

code:

#include <iostream>
using namespace std;
struct link //one element of list
{
    int data; //data item
    link* next; //pointer to next link
};
class linklist //a list of links
{
    private:
        link* first; //pointer to first link   !!!!!!!!Here is the first error ~!!!!!!!!!!!
    public:
        linklist() //no-argument constructor
        {
            first = NULL;
        } //no first link
        void additem(int d); //add data item (one link)
        void display(); //display all links
};
void linklist::additem(int d) //add data item
{
    link* newlink = new link; //make a new link
    newlink->data = d; //give it data
    newlink->next = first; //it points to next link
    first = newlink; //now first points to this
}
void linklist::display() //display all links
{
    link* current = first; //set ptr to first link
    while( current != NULL ) //quit on last link
    {
    cout << current->data << endl; //print data
    current = current->next; //move to next link
    }
}
int main()
{
        linklist li; //make linked list
        li.additem(25); //add four items to list
        li.additem(36);
        li.additem(49);
        li.additem(64);
        li.display(); //display entire list
        return 0;
}

Answer 1

The problem is that the name link is conflict with a function named link in unistd.h. Try with g++ on the OS X.

Answer 2

As far as I can tell you are probably building this as C code, if I build using g++ it works just fine but if I use gcc the first error is:

error: 'link' does not name a type

So I can reproduce this on g++ by adding:

#include <unistd.h>

So it looks like the name link conflicts with something in that header file. Renaming link to another name seems to fix the issue.