So I made a relatively simple OpenGL program that makes a small line segment spin counter-clockwise across a fixed point by using some polar coordinate maths. When I run this program in Visual Studio, I can see in the diagnostic tools that my process memory in climbing up to nearly a gig of memory. When I reach about 700 megs, the program just stops running and I get this exception:
Exception thrown at 0x102C333E (ig9icd32.dll) in GL_Playground.exe: 0xC0000005: Access violation writing location 0x00000000.
I’m thinking that yes, each time I call CreateLines in the draw loop, it makes a new array of GLfloat s on the stack. But shouldn’t all this data be deleted automatically at the end of the scope’s life? Here is the full code:
#include <iostream>
#include <stdio.h>
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <string>
#include "util.h"
#include <thread>
#include <chrono>
#include <cmath>
// Setup: Linker->General, Linker->Input, add that .dll next to main
// Window dimensions
const GLint WIDTH = 1720, HEIGHT = 1600; // height was 1200
GLuint VAO, VBO, shader;
int numberOfVerticies = 2; // number of full points we want to draw
long long int index = 0;
// Vertex shader -> takes each vertex and allows you manipulate them then pass them onto the fragmanet shader
// In the shaders you are writing GLSL
static const char* vShader = " \n\
#version 330 \n\
layout (location = 0) in vec3 pos; \n\
\n\
void main() \n\
{ \n\
gl_Position = vec4(pos.x, pos.y, pos.z, 1.0); \n\
\n\
\n\
}";
// Fragment shader
static const char* fShader = " \n\
#version 330 \n\
out vec4 colour; \n\
\n\
void main() \n\
{ \n\
colour = vec4(1.0, 1.0, 1.0, 1.0); \n\
\n\
\n\
}";
void CreateLines()
{
GLfloat verticies[12];
util::addToArray(verticies, index);
glGenVertexArrays(1, &VAO); // Reserves space on the graphics card to be accessed by the variable VAO
// Now we bind the Vertex Array so now any opengl functions we use that interact with vertext arrays or vertex buffers will all be taking place within this vertex array defined by VAO
glBindVertexArray(VAO);
glGenBuffers(1, &VBO);
glBindBuffer(GL_ARRAY_BUFFER, VBO);
// Static draw used when you aren't going to be changing the values in the actual array
glBufferData(GL_ARRAY_BUFFER, sizeof(verticies), verticies, GL_DYNAMIC_DRAW); // Just changing to dynamic didn't make a bug
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0); // location of attribute, values at a time, type of those values, normalization, stride, offset
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, 0); // Unbind
glBindVertexArray(0); // Unbind
}
void AddShader(GLuint theProgram, const char* shaderCode, GLenum shaderType)
{
GLuint theShader = glCreateShader(shaderType); // Creates an empty shader of that type and pass ID into theShader
const GLchar* theCode[1];
theCode[0] = shaderCode;
GLint codeLength[1];
codeLength[0] = strlen(shaderCode);
glShaderSource(theShader, 1, theCode, codeLength); // This modifies the value of the shader code in memory
glCompileShader(theShader);
GLint result = 0;
GLchar eLog[1024] = { 0 };
glGetShaderiv(theShader, GL_COMPILE_STATUS, &result); // Gets result of linking the shader
if (!result)
{
glGetShaderInfoLog(theShader, sizeof(eLog), NULL, eLog);
printf("Error compiling the %d shader: '%s'\n", shaderType, eLog);
return;
}
glAttachShader(theProgram, theShader);
}
// Compiling the shaders, not handling adding the shaders to the program
void CompileShaders()
{
shader = glCreateProgram(); // Creates the program and gives shader the id so we can use shader to modify it
if (!shader)
{
printf("Error creating shader\n");
return;
}
AddShader(shader, vShader, GL_VERTEX_SHADER); // GL_VERTEX_SHADER is a built in enum -> type of shader -> needs to know what type of shader is being used
AddShader(shader, fShader, GL_FRAGMENT_SHADER);
GLint result = 0;
GLchar eLog[1024] = { 0 };
glLinkProgram(shader); // Actually create the executables on the graphics card and make sure it's working
glGetProgramiv(shader, GL_LINK_STATUS, &result); // Gets result of linking the shader
if (!result)
{
glGetProgramInfoLog(shader, sizeof(eLog), NULL, eLog);
printf("Error linking program: '%s'\n", eLog);
return;
}
// Validate the program
glValidateProgram(shader); // Makes sure the shader is valid in the current context that we're working in
glGetProgramiv(shader, GL_VALIDATE_STATUS, &result); // Gets result of linking the shader
if (!result)
{
glGetProgramInfoLog(shader, sizeof(eLog), NULL, eLog);
printf("Error validating program: '%s'\n", eLog);
return;
}
}
int main()
{
// Initialize GLFW
if (!glfwInit())
{
printf("GLFW initialization failed!");
glfwTerminate();
std::cin.get();
return 1;
}
// Setup GLFW window properties
// OpenGL version
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
// Core profile = No backwards compatabililty
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
// Allow forward compatibility
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
GLFWwindow* mainWindow = glfwCreateWindow(WIDTH, HEIGHT, "Playground", NULL, NULL);
if (!mainWindow)
{
printf("GLFW window creation failed");
glfwTerminate();
std::cin.get();
return 1;
}
// Get buffer size information
// We want to get the dimentions of the area in the middle of the window, it's the buffer, it's the part that's going to be holding all the openGL data as it's being passed to the window
int bufferWidth, bufferHeight;
glfwGetFramebufferSize(mainWindow, &bufferWidth, &bufferHeight);
// Set the context for GLEW to use
// Let GLEW know that this OpenGL context is the one everything should be tied to so when everything gets drawn it should get drawn to this window
glfwMakeContextCurrent(mainWindow);
// Allow modern extension features
glewExperimental = GL_TRUE;
if (glewInit() != GLEW_OK)
{
printf("GLEW initilisation failed!");
glfwDestroyWindow(mainWindow);
glfwTerminate();
std::cin.get();
return 1;
}
// Setup viewport size
// There is a difference here between WIDTH and bufferWidth, should look into
glViewport(0, 0, bufferWidth, bufferHeight);
// CreateLines();
// CompileShaders();
int i = 0;
// Loop until window closed
while (!glfwWindowShouldClose(mainWindow))
{
// Get and handle user input events
glfwPollEvents(); // will check for any user events
CreateLines();
CompileShaders();
index++;
// Clear the window
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shader); // Grabs the id then goes to the graphics card and says to use the one with the ID of shader
// Everything below here will be using this shader
glBindVertexArray(VAO);
// Now using that VAO
glDrawArrays(GL_LINES, 0, numberOfVerticies); // Mode, where to start in the array, the ammount of points we want to draw
glBindVertexArray(0);
glUseProgram(0); // Unassignes shader
glfwSwapBuffers(mainWindow); // We are drawing to a hidden buffer that constantly gets swapped around
}
std::cin.get();
return 0;
}
