Exception thrown at 0x00000000 in opengl

support
#1

hey very new to OpenGL just started watching a video tutorial and I’m getting this error Exception thrown at 0x00000000 in opengl.exe: 0xC0000005: Access violation executing location 0x00000000. occurred it happens on the first glCreateShader

#include <iostream>

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

#include <GLFW/glfw3.h>

const GLchar* vertexShaderSource = "#version 330 core\n"
"layout ( location = 0 ) in vec3 position;\n"
"void main( )\n"
"{\n"
"gl_Position = vec4( position.x, position.y, position.z, 1.0 );\n"
"}\n";

const GLchar* fragmentShaderSource = "#version 330 core\n"
"out vec4 color;\n"
"void main( )\n"
"{\n"
"color = vec4( 1.0f, 0.5f, 0.2f, 1.0f );\n"
"}\n";

int main(void)
{
    GLFWwindow* window;

    /* Initialize the library */
    if (!glfwInit())
        return -1;

    GLenum err = glewInit();

    /* Create a windowed mode window and its OpenGL context */
    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    /* Make the window's context current */
    glfwMakeContextCurrent(window);

    GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertexShader, 1, &vertexShaderSource, NULL);
    glCompileShader(vertexShader);

    GLint success;
    GLchar infoLog[512];

    glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &success);

    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "error (vertex)\n" << infoLog << std::endl;
    }

    GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragmentShader, 1, &fragmentShaderSource, NULL);
    glCompileShader(fragmentShader);

    glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &success);

    if (!success) 
    {
        glGetShaderInfoLog(fragmentShader, 512, NULL, infoLog);
        std::cout << "error (fragment)\n" << infoLog << std::endl;
    }

    GLuint shaderProgram = glCreateProgram();
    glAttachShader(shaderProgram, vertexShader);
    glAttachShader(shaderProgram, fragmentShader);
    glLinkProgram(shaderProgram);

    glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success);

    if (!success)
    {
        glGetShaderInfoLog(vertexShader, 512, NULL, infoLog);
        std::cout << "error (program linking failed)\n" << infoLog << std::endl;
    }

    glDeleteShader(vertexShader);
    glDeleteShader(fragmentShader);

    GLfloat vertices[] =
    {
        -0.5f, -0.5f, 0.0f, //bottem left
        0.5f, -0.5f, 0.0f, //bottem right
        0.0f, 0.5f, 0.0f
    };
    GLuint VBO, VAO;
    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);
    
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
    glEnableVertexAttribArray(0);

    glBindBuffer(GL_ARRAY_BUFFER, 0);

    glBindVertexArray(0);

    /* Loop until the user closes the window */
    while (!glfwWindowShouldClose(window))
    {
        /* Render here */
        glClear(GL_COLOR_BUFFER_BIT);

        glUseProgram(shaderProgram);
        glBindVertexArray(VAO);
        glDrawArrays(GL_TRIANGLES, 0, 3);
        glBindVertexArray(0);

        /* Swap front and back buffers */
        glfwSwapBuffers(window);

        /* Poll for and process events */
        glfwPollEvents();
    }

    glDeleteVertexArrays(1, &VAO);
    glDeleteBuffers(1, &VBO);

    glfwTerminate();
    return 0;
}
#2

My guess would be that the function glCreateShader is NULL, i.e. GLEW was unable to load the extension. Have you checked that your driver supports this OpenGL feature (OpenGL 2.0 or the extension)?

#3

You can ask GLFW to ensure the OpenGL context is version 3.3 (based on 330 in the shaders) or later by setting window hints between init and window creation:

glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);

Then if version 3.3 is unavailable, glfwCreateWindow will fail.

#4

The problem is that GLEW is initialized before OpenGL context is created and made current.
You should call glewInit() after glfwMakeContextCurrent() function.