Access violation inside glfwPollEvents()?

Question

When I start my program:

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>

struct ShaderProgramSource
{
    std::string VertexSource;
    std::string FragmentSource;
};

static ShaderProgramSource parseShader(const std::string& filepath)
{
    std::ifstream stream(filepath);

    enum class ShaderType
    {
        NONE = -1, VERTEX = 0, FRAGMENT = 1
    };

    std::string line;
    std::stringstream ss[2];
    ShaderType type = ShaderType::NONE;
    while (getline(stream, line))
    {
        if (line.find("#shader") != std::string::npos)
        {
            if (line.find("vertex") != std::string::npos)
                type = ShaderType::VERTEX;
            else if (line.find("fragment") != std::string::npos)
                type = ShaderType::FRAGMENT;
        }
        else
        {
            ss[(int)type] << line << '\n';
        }
    }

    return { ss[0].str(), ss[1].str() };
}

typedef unsigned int uint;

static uint compileShader(const std::string& source, uint type)
{
    uint id = glCreateShader(type);
    const char* src = source.c_str();
    glShaderSource(id, 1, &src, nullptr);
    glCompileShader(id);

    int result;
    glGetShaderiv(id, GL_COMPILE_STATUS, &result);
    if (result == GL_FALSE)
    {
        int length;
        glGetShaderiv(id, GL_INFO_LOG_LENGTH, &length);
        //char* message = (char*)alloca(length * sizeof(char));
        char* message = new char[length];
        glGetShaderInfoLog(id, length, &length, message);
        std::cout << "Failed to compile the " << (type == GL_VERTEX_SHADER ? "vertex" : "fragment")
            << " shader !" << std::endl;
        std::cout << message << std::endl;
        delete[](message);
        glDeleteShader(id);
        return EXIT_FAILURE;
    }

    return id;
}

static uint CreateShader(const std::string& vertexShader, const std::string& fragmentShader)
{
    uint program = glCreateProgram();
    uint vs = compileShader(vertexShader, GL_VERTEX_SHADER);
    uint fs = compileShader(fragmentShader, GL_FRAGMENT_SHADER);

    glAttachShader(program, vs);
    glAttachShader(program, fs);
    glLinkProgram(program);
    glValidateProgram(program);

    glDeleteShader(vs);
    glDeleteShader(fs);

    return program;
}

int main(void)
{
    GLFWwindow* window;

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

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

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

    auto state = glewInit();
    if (state != GLEW_OK)
    {
        std::cerr << "Error initializing GLEW" << std::endl;
        return EXIT_FAILURE;
    }

    std::cout << glGetString(GL_VERSION) << std::endl;

    float positions[6] = {
        -0.5f, -0.5f,
         0.0f,  0.5f,
         0.5f, -0.5f
    };

    unsigned int buffer;
    glGenBuffers(1, &buffer);
    glBindBuffer(GL_ARRAY_BUFFER, buffer);
    glBufferData(GL_ARRAY_BUFFER, 6 * sizeof(float), positions, GL_STATIC_DRAW);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 2, 0);

    ShaderProgramSource source = parseShader("res/shaders/basic.shader");

    std::cout << "VERTEX" << std::endl;
    std::cout << source.VertexSource << std::endl;
    std::cout << "FRAGMENT" << std::endl;
    std::cout << source.FragmentSource << std::endl;

    //uint shader = CreateShader(source.VertexSource, source.VertexSource);
    //glUseProgram(shader);

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

        glDrawArrays(GL_TRIANGLES, 0, 3);

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

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

    //glDeleteProgram(shader);

    glfwTerminate();
    return 0;
}

...everything work well but just a few seconds later, the app crash. it return the exit code -1073741819 and by converting it into hex, I find that's the error code C0000005: buffer overrun. Then I decided to debug that and the debugger said that:

"Exception thrown at 0x00007FFD28144921 (igxelpicd64.dll) in App.exe: 0xC0000005: Access violation writing location 0x0000025170620000."

Answer 1

It seems that you are not using your shader as you have glCompileShader() and glUseProgram(shader) commented out and OpenGL does not have default one. Try to uncomment those 2 lines and leave glCompileShader where it is (before the main loop) but move the glUseShader(shader) to the rendering loop just before you call 'glDrawArrays()`

Also I don't see that you are creating VertexArrayObject which needs to be created and bound using glBindVertexArray(GLint: VAO), instead you use regular buffer as VertexArrayBuffer so your code for creating VertexArrayBuffer should look like this

unsigned int VAO, VBO;

//this is missing in your code
glGenVertexArrays(1, &VAO);
glGenBuffers(1, &VBO);
glBindVertexArray(VAO);

glBindBuffer(GL_ARRAY_BUFFER, VBO);
glBufferData(GL_ARRAY_BUFFER, sizeof(positions), &positions GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
glBindVertexArrays(0)

Now when you have Vertex arrays you can render you triangle using the following

//while loop

glUseProgram(shaderProgram)
glBindVertexArrays(VAO)
glDrawArray(GL_TRIANGLES, 0, 3);

//----------

This shoudl solve your issue assuming your shades are correctly compiled and you pass everything to the VertexArrayBuffer.