OpenGL Hello Triangle Errors


I am trying to run the simple shaders to run; however when I try to run the code, I get an error saying "Exception thrown at 0x00000000 in OpenGL_Triangle.exe: 0xC0000005: Access violation executing location 0x00000000." in the separate loadShader file.

I tried running it underneath the GLEW initialization in my main file without using "GLuint LoadShaders(const char* vertex_file_path, const char* fragment_file_path){}" and "return ProgramID;" and defining LoadShaders as a separate unsigned int, and setting the "program" integer equal to the "ProgramID" integer from the loadShader file.

I don't exactly know what to do now.

*Just as a note I am using Visual Studio 2019.

// This is my main file (titled: main.cpp)
// Include standard headers
#include <stdio.h>
#include <stdlib.h>

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <glm/glm.hpp>
using namespace glm;

#include <string>
#include <vector>
#include <fstream>
#include <algorithm>
#include <sstream>
#include <string.h>

#include <iostream>
using namespace std;

 #include <common/shader.hpp>

// Create and compile our GLSL program from the shaders
GLuint program = LoadShaders("vertex.shader", "fragment.shader");

int main() {

    // Initialise GLFW
    glewExperimental = true; // Needed for core profile
    if (!glfwInit())
        cout << "Failed to initialize GLFW\n";
        return -1;

    cout << "Hello Triangle \n" ;

    glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); // We want OpenGL 3.3
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    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
    GLFWwindow* window; // (In the accompanying source code, this variable is global for simplicity)
    window = glfwCreateWindow(500, 500, "Test", NULL, NULL);
    if (window == NULL) {
        cout << "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";
        return -1;

    // Initialize GLEW
    glewExperimental = true; // Needed in core profile
    if (glewInit() != GLEW_OK) {
        cout << "Failed to initialize GLEW from main\n";
        return -1;

    GLuint VertexArrayID;
    glGenVertexArrays(1, &VertexArrayID);

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

    // This will identify our vertex buffer
    GLuint vertexbuffer;
    // Generate 1 buffer, put the resulting identifier in vertexbuffer
    glGenBuffers(1, &vertexbuffer);
    // The following commands will talk about our 'vertexbuffer' buffer
    glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
    // Give our vertices to OpenGL.
    glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STATIC_DRAW);

    do {
        // Clear the screen. It's not mentioned before Tutorial 02, but it can cause flickering, so it's there nonetheless.

        // Use our shader

        // Drawing
// 1st attribute buffer : vertices
        glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
            0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
            3,                  // size
            GL_FLOAT,           // type
            GL_FALSE,           // normalized?
            0,                  // stride
            (void*)0            // array buffer offset
        // Draw the triangle !
        glDrawArrays(GL_TRIANGLES, 0, 3); // Starting from vertex 0; 3 vertices total -> 1 triangle
        // Swap buffers



    } // Check if the ESC key was pressed or the window was closed
    while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
        glfwWindowShouldClose(window) == 0);
// This is my LoadShaders file (titled: loadShader.cpp)
#include <stdio.h>
#include <string>
#include <vector>
#include <iostream>
#include <fstream>
#include <algorithm>
#include <sstream>
using namespace std;
#include <string.h>

#include <stdlib.h>

#include <GL/glew.h>

#include "common/shader.hpp"

GLuint LoadShaders(const char* vertex_file_path, const char* fragment_file_path) {

    // Create the shaders
    GLuint VertexShaderID = glCreateShader(GL_VERTEX_SHADER);
    GLuint FragmentShaderID = glCreateShader(GL_FRAGMENT_SHADER);

    // Read the Vertex Shader code from the file
    std::string VertexShaderCode;
    std::ifstream VertexShaderStream(vertex_file_path, std::ios::in);
    if (VertexShaderStream.is_open()) {
        std::stringstream sstr;
        sstr << VertexShaderStream.rdbuf();
        VertexShaderCode = sstr.str();
    else {
        printf("Impossible to open %s. Are you in the right directory ? Don't forget to read the FAQ !\n", vertex_file_path);
        return 0;

    // Read the Fragment Shader code from the file
    std::string FragmentShaderCode;
    std::ifstream FragmentShaderStream(fragment_file_path, std::ios::in);
    if (FragmentShaderStream.is_open()) {
        std::stringstream sstr;
        sstr << FragmentShaderStream.rdbuf();
        FragmentShaderCode = sstr.str();

    GLint Result = GL_FALSE;
    int InfoLogLength;

    // Compile Vertex Shader
    printf("Compiling shader : %s\n", vertex_file_path);
    char const* VertexSourcePointer = VertexShaderCode.c_str();
    glShaderSource(VertexShaderID, 1, &VertexSourcePointer, NULL);

    // Check Vertex Shader
    glGetShaderiv(VertexShaderID, GL_COMPILE_STATUS, &Result);
    glGetShaderiv(VertexShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    if (InfoLogLength > 0) {
        std::vector<char> VertexShaderErrorMessage(InfoLogLength + 1);
        glGetShaderInfoLog(VertexShaderID, InfoLogLength, NULL, &VertexShaderErrorMessage[0]);
        printf("%s\n", &VertexShaderErrorMessage[0]);

    // Compile Fragment Shader
    printf("Compiling shader : %s\n", fragment_file_path);
    char const* FragmentSourcePointer = FragmentShaderCode.c_str();
    glShaderSource(FragmentShaderID, 1, &FragmentSourcePointer, NULL);

    // Check Fragment Shader
    glGetShaderiv(FragmentShaderID, GL_COMPILE_STATUS, &Result);
    glGetShaderiv(FragmentShaderID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    if (InfoLogLength > 0) {
        std::vector<char> FragmentShaderErrorMessage(InfoLogLength + 1);
        glGetShaderInfoLog(FragmentShaderID, InfoLogLength, NULL, &FragmentShaderErrorMessage[0]);
        printf("%s\n", &FragmentShaderErrorMessage[0]);

    // Link the program
    printf("Linking program\n");
    GLuint ProgramID = glCreateProgram();
    glAttachShader(ProgramID, VertexShaderID);
    glAttachShader(ProgramID, FragmentShaderID);

    // Check the program
    glGetProgramiv(ProgramID, GL_LINK_STATUS, &Result);
    glGetProgramiv(ProgramID, GL_INFO_LOG_LENGTH, &InfoLogLength);
    if (InfoLogLength > 0) {
        std::vector<char> ProgramErrorMessage(InfoLogLength + 1);
        glGetProgramInfoLog(ProgramID, InfoLogLength, NULL, &ProgramErrorMessage[0]);
        printf("%s\n", &ProgramErrorMessage[0]);

    glDetachShader(ProgramID, VertexShaderID);
    glDetachShader(ProgramID, FragmentShaderID);


    return ProgramID;
// This is the Shader header file (titled; shader.hpp)
// It was placed int the include directories folder in another folder titled "common"
#ifndef SHADER_HPP
#define SHADER_HPP

#include "GL/glew.h"

GLuint LoadShaders(const char* vertex_path, const char* fragment_path);


asked on Stack Overflow Jun 17, 2020 by Ryan Foster • edited Jun 18, 2020 by genpfault

1 Answer

GLuint program = LoadShaders("vertex.shader", "fragment.shader");

int main() {

Don't try to execute GL commands before you have initialized GLEW. Otherwise you're going to call a NULL function-pointer like glCreateShader() and your process is Going To Have A Bad Time.

Move that LoadShaders() call to after glewInit().

answered on Stack Overflow Jun 18, 2020 by genpfault

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