OpenGL 4.1 on OSX Xcode 6 setup difficulties

Question

I'm trying to learn some OpenGL and immediately found out versions of OpenGL >3.2 were the more relevant ones to learn.

So I've set up my Mac OS X 10.10.3 with Xcode and command line tools to get some examples going.

But jebus this thing is being a pain in the butt.

The error I'm getting is.

    Undefined symbols for architecture x86_64:
  "LoadShaders(char const*, char const*)", referenced from:
      _main in main.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

So I have the most recent version of GLFW GLEW cmake to get things going.

I add my header and library paths to the project.

Library Search Paths

/opt/X11/lib /usr/lib/ /Users/mac/Dev/workspace/C++/Test/glfw/build/src/Debug /Users/mac/Dev/workspace/C++/Test/glew/lib

• I add the last two directories just to double up on the directory

Header Search Path look similar with include instead of lib

my linkers are vast (from trying random things)

-framework OpenGl -lGLUT -lglew -lglfw -lGL -lGLU -lXmu -lXi -lXext -lX11 -lXt

and I've linked the Binaries with the Libraries as well. Where am I going wrong?? my GPU is the Intel HD 4000 and appears to support up to OpenGL4.1.

Do I need to add compiler flags? Is this just not plausible?

Here's the tutorial code that I'm trying to run.

    #include <stdio.h>
#include <stdlib.h>

//GLEW
#define GLEW_STATIC
#include <GL/glew.h>

#include <GLUT/glut.h>

//GLFW
#include <GLFW/glfw3.h>
#include <AGL/glm.h>

GLFWwindow* window;

//no real explanation of what this is.....
#include <common/shader.hpp>

//MAIN FUNCTION
int main(int argc, char *argv[])
{
    if( !glfwInit() )
    {
        fprintf( stderr, "Failed to initialize GLFW\n" );
        return -1;
    }

    // specify GL information
    glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); // We want 4.1>= OpenGL_version >=3.3
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // To make MacOS happy; should not be needed
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); //We don't want the old OpenGL

    // Open a window and create its OpenGL context
    window = glfwCreateWindow( 600, 375, "Tutorial 02", NULL, NULL);

    if( window == NULL ){
        fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
        glfwTerminate();
        return -1;
    }
    glfwMakeContextCurrent(window);


    // Initialize GLEW
    glewExperimental=true; // Needed in core profile
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to initialize GLEW\n");
        return -1;
    }
    // Ensure we can capture the escape key being pressed below
    glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

    // Dark blue background
    glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

    // Create Vertex Array Object.
    GLuint VertexArrayID;
    glGenVertexArrays(1, &VertexArrayID);
    glBindVertexArray(VertexArrayID);

    // Create and compile our GLSL program from the shaders
    GLuint programID = LoadShaders( "SimpleVertexShader.vertexshader", "SimpleFragmentShader.fragmentshader" );

    // An array of 3 vectors which represents 3 vertices
    static const GLfloat g_vertex_buffer_data[] = {
        -1.0f, -1.0f, 0.0f,
        1.0f, -1.0f, 0.0f,
        0.0f,  1.0f, 0.0f,
    };

    GLuint vertexbuffer;
    glGenBuffers(1, &vertexbuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

    do{
        // Clear the screen
        glClear( GL_COLOR_BUFFER_BIT );

        // Use our Shader
        glUseProgram(programID);

        // 1st attribute buffer : vertices
        glEnableVertexAttribArray(0);
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);

        // glVertexAttribPointer(
        //                          Atrribute,
        //                          size,
        //                          type,
        //                          normalized,
        //                          stride,
        //                          array buffer offset
        //                      );
        glVertexAttribPointer( 0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);

        // Draw the triangle
        glDrawArrays(GL_TRIANGLES, 0, 3);

        glDisableVertexAttribArray(0);

        // Swap buffers
        glfwSwapBuffers(window);
        glfwPollEvents();

    } // Check if the ESC key was pressed or the window was closed
    while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
          glfwWindowShouldClose(window) == 0 );

    // Cleanup VBO
    glDeleteBuffers(1, &vertexbuffer);
    glDeleteVertexArrays(1, &VertexArrayID);
    glDeleteProgram(programID);

    // Close OpenGL window and terminate GLFW
    glfwTerminate();

    return 0;
}

I mostly followed this guideline here Oscar Chavez, Setup instructions

Answer 1

//no real explanation of what this is.....
#include <common/shader.hpp>

Probably something the author of that tutorial wrote himself and simply dumped into the project sources, without telling anything more. The most annoying part about this lines is the use of wedge brackets (<…>) instead of quotes ("…") because this misleadingly suggests that the header is part of the system libraries and not something local to the project. Somwehere there likely is a common/shader.cpp and therein will probably be a function LoadShaders. It is this very function, that is something completely custom, not something part of OpenGL or any of the helper libraries, which your linker is telling you to be amiss.

Answer 2

The function LoadShaders() is not part of OpenGL, and it is not part of any of the libraries you are using (I see GLEW and GLFW). In short, LoadShaders() is missing.

My guess is that LoadShaders() is a function that the author of the tutorial wrote, but the formatting for the tutorial is a bit frustrating (to say the least!) so I'm not sure.