C++ linker error after overloading an operator - xcode

Question

I keep getting the following error when I try to compile an example program from C++ how to program, Deitel and Deitel. I used g++ Fig11_05.cpp -o Fig11_05
I spent hours trying to solve this problem by looking up the Internet and particularly stackoverflow, but with no avail!
I tried using different command line arguments such as -libstd=libc++, -std=c++11, -std=c++14
the error I keep getting is as this:
Undefined symbols for architecture x86_64:
"operator<<(std::__1::basic_ostream >&, PhoneNumber const&)", referenced from:
_main in Fig11_05-1f04bd.o
"operator>>(std::__1::basic_istream >&, PhoneNumber&)", referenced from:
_main in Fig11_05-1f04bd.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
The result of g++ -v:
Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk/usr/include/c++/4.2.1
Apple LLVM version 8.0.0 (clang-800.0.42.1)
Target: x86_64-apple-darwin15.6.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
The codes:
// Fig. 11.3: PhoneNumber.h
// PhoneNumber class definition
#ifndef PHONENUMBER_H
#define PHONENUMBER_H
#include <iostream>
#include <string>
class PhoneNumber
{
friend std::ostream& operator<<(std::ostream&, const PhoneNumber&);
friend std::istream &operator>>(std::istream&, PhoneNumber&);
private:
std::string areaCode; // 3-digit area code
std::string exchange; // 3-digit exchange
std::string line; // 4-digit line
}; // end class PhoneNumber
#endif
// Fig. 11.4: PhoneNumber.cpp
// Overloaded stream insertion and stream extraction operators
// for class PhoneNumber.
#include <iomanip>
#include "PhoneNumber.h"
using namespace std;
// overloaded stream insertion operator; cannot be
// a member function if we would like to invoke it with
// cout << somePhoneNumber;
ostream& operator<<(ostream& output, const PhoneNumber& number)
{
output << "Area Code: " << number.areaCode << "\nExchange: "
<< number.exchange << "\nLine: " << number.line << "\n"
<< "(" << number.areaCode << ") " << number.exchange << "-"
<< number.line << "\n";;
return output; // enables cout << a << b << c;
} // end function operator<<
// overloaded stream extraction operator; cannot be
// a member function if we would like to invoke it with
// cin >> somePhoneNumber;
istream& operator>>(istream& input, PhoneNumber& number)
{
input.ignore(); // skip (
input >> setw(3) >> number.areaCode; // input area code
input.ignore(2); // skip ) and space
input >> setw(3) >> number.exchange; // input exchange
input.ignore(); // skip dash (-)
input >> setw(4) >> number.line; // input line
return input; // enables cin >> a >> b >> c;
} // end function operator>>
// Fig. 11.5: fig11_05.cpp
// Demonstrating class PhoneNumber's overloaded stream insertion
// and stream extraction operators.
#include <iostream>
#include "PhoneNumber.h"
using namespace std;
int main()
{
PhoneNumber phone; // create object phone
cout << "Enter phone number in the form [phone]:" << endl;
// cin >> phone invokes operator>> by implicitly issuing
// the global function call operator>>( cin, phone )
cin >> phone;
cout << "\nThe phone number entered was:\n";
// cout << phone invokes operator<< by implicitly issuing
// the global function call operator<<( cout, phone )
cout << phone << endl;
} // end main
Note: I recently installed then uninstalled CUDA toolkit 8. I needed a newer version of Xcode, so I installed Xcode the newest version 8.2.1, and kept the old version in a different directory just in case. I don't think the problem is with the installation of Xcode though. Also when I installed CUDA I had to set DYLD_LIBRARY_PATH to a directory. However, it might not be the source of the problem! I am just trying to help you figure out the problem to help me fix it :)
Thank you in advance! You are such a good community!

Answer 1

Your attempt to build the program:
g++ Fig11_05.cpp -o Fig11_05
is unsuccessful because you have neglected to compile and link into the
program the code that contains the definitions of the functions:
std::ostream& operator<<(std::ostream& output, const PhoneNumber& number)
and:
std::istream& operator>>(std::istream& input, PhoneNumber& number)
which are called by your program. That is why the linker says:
Undefined symbols for architecture x86_64:
"operator<<(std::__1::basic_ostream >&, PhoneNumber const&)", referenced from: _main in Fig11_05-1f04bd.o
"operator>>(std::__1::basic_istream >&, PhoneNumber&)", referenced from: _main in Fig11_05-1f04bd.o
...
Do this instead:
g++ Fig11_05.cpp PhoneNumber.cpp -o Fig11_05
Or to spell out the process in full:-
Compile source file Fig11_05.cpp to object file Fig11_05.o:
$ g++ -o Fig11_05.o -c Fig11_05.cpp
Compile source file PhoneNumber.cpp to object file PhoneNumber.o:
$ g++ -o PhoneNumber.o -c PhoneNumber.cpp
Link the object files Fig11_05.o and PhoneNumber.o into program Fig11_05
$ g++ -o Fig11_05 Fig11_05.o PhoneNumber.o
You can then run:
./Fig11_05
Here is a fairly good beginner's tutorial
about building C or C++ programs with GCC.