c++ undefined symbol when compiling

FIXED: had the method twice in the header file

I get the following error when trying to compile my project

% make
g++ -o p4 testTree.o tree.o node.o check.o
Undefined first referenced symbol in file
Tree::inTree(int) tree.o
ld: fatal: Symbol referencing errors. No output written to p4
collect2: ld returned 1 exit status
*** Error code 1
make: Fatal error: Command failed for target `p4'

Makefile

p4: testTree.o tree.o node.o check.o g++ -o p4 testTree.o tree.o node.o check.o
testTree.o: testTree.cc tree.h node.h check.h g++ -c -Wall -Werror testTree.cc
tree.o: tree.h tree.cc node.h check.h g++ -c -Wall -Werror tree.cc
node.o: node.h node.cc check.h g++ -c -Wall -Werror node.cc
check.o: check.h check.cc g++ -c -Wall -Werror check.cc
clean: rm -f *~ *.o p4

Relevant code from tree.cc and tree.h:

tree.cc

...
bool Tree::inTree(int k) const
{ return locate(k,root) != NULL;
}
...

tree.h

#ifndef TREE_H
#define TREE_H
#include "node.h"
#include "check.h"
using namespace std;
class Tree
{ private: Node *root; public: Tree(); Tree(const Tree & t); const Tree & operator=(const Tree &t); friend ostream & operator<<(ostream &out, const Tree &t); bool inTree(int k) const; double & operator[](int k); double & operator[](int k) const; ~Tree(); bool inTree(int index); private: Node * locate(int k, Node *rt) const; ostream & display(ostream &out, Node *r, int dir=Node::L) const; void add(int k, Node*&r); void kill(Node *&rt); void copy(Node *rt, Node *&newRt);
};
#endif

I get the feeling that it's something really simple, but I can't seem to figure it out.

2 Answers

The message you are getting actually comes from the linker, not from the compiler.

One of your member functions, bool Tree::inTree(int index);, is correctly declared and defined as a const member function:

 // Declaration in tree.h bool inTree(int index) const; // Definition in tree.cc bool Tree::inTree(int k) const // ^^^^^

However, in tree.h you also define this non-const overload of inTree():

// Declaration in tree.h, definition (supposedly) nowhere
bool Tree::inTree(int k)

For which no definition is provided. This is what the linker complains about.

Here is your error:

bool Tree::inTree(int k) const
{ return locate(k,root) != NULL;
}

in your .h you define

bool inTree(int);

This is a difference!