Question

I’m lost here. I’ve been compiling my program successfully on LLVM on my Mac, but when I went to a Linux server and attempted to use g++ to compile, I got a boat load of linker errors.

Here’s an excerpt:

/tmp/ccGbgd6T.o: In function `Scene::setBackgroundImage(String)':
Project.cpp:(.text+0x166): undefined reference to `Graph_lib::Image::Image(Point, String, Graph_lib::Suffix::Encoding)'
/tmp/ccGbgd6T.o: In function `Graph_lib::Window::~Window()':
Project.cpp:(.text._ZN9Graph_lib6WindowD2Ev[_ZN9Graph_lib6WindowD5Ev]+0xc): undefined reference to `vtable for Graph_lib::Window'
/tmp/ccGbgd6T.o: In function `Graph_lib::Shape::~Shape()':
Project.cpp:(.text._ZN9Graph_lib5ShapeD2Ev[_ZN9Graph_lib5ShapeD5Ev]+0xb): undefined reference to `vtable for Graph_lib::Shape'
/tmp/ccGbgd6T.o: In function `Graph_lib::Text::Text(Point, String const&)':
Project.cpp:(.text._ZN9Graph_lib4TextC2E5PointRK6String[_ZN9Graph_lib4TextC5E5PointRK6String]+0xe): undefined reference to `Graph_lib::Shape::Shape()'
Project.cpp:(.text._ZN9Graph_lib4TextC2E5PointRK6String[_ZN9Graph_lib4TextC5E5PointRK6String]+0x17): undefined reference to `vtable for Graph_lib::Text'
Project.cpp:(.text._ZN9Graph_lib4TextC2E5PointRK6String[_ZN9Graph_lib4TextC5E5PointRK6String]+0x67): undefined reference to `Graph_lib::Shape::add(Point)'
/tmp/ccGbgd6T.o: In function `Graph_lib::Button::Button(Point, int, int, String const&, void (*)(void*, void*))':
Project.cpp:(.text._ZN9Graph_lib6ButtonC2E5PointiiRK6StringPFvPvS5_E[_ZN9Graph_lib6ButtonC5E5PointiiRK6StringPFvPvS5_E]+0x40): undefined reference to `vtable for Graph_lib::Button'

This scared me, but then I noticed that all the errors are coming from the same class: Graph_lib. Here’s an extremely cut out version of what Graph.h looks like: (note, this is not my class)

#ifndef GRAPH_GUARD
#define GRAPH_GUARD 1

#include <...system stuff...>

namespace Graph_lib {
// lots of other classes in here
// this is just one
    struct Image : Shape {
        Image(Point xy, string file_name, Suffix::Encoding e = Suffix::none);
    //rest of class
    }
}

What could be going wrong here?

Edit: this is the command I’m using to compile:

g++-4.6 -std=c++0x *.cpp -lfltk -lfltk_images

Answer 1

It appears as though you have forgotten to link your project with Graph.cpp, or whatever file(s) hold the implementations of the Graph_lib class methods.