Opengl Thread 1: EXC_BAD_ACCESS (code=1, address=0x0) - c++

Question

I making an OpenGL video game using GLFW version 2. I am getting an error I do not understand
The following code is:
//
// GameWindow.cpp
// RocketGame
//
// Created by Vaibhav Malhotra on 12/5/17.
// Copyright © 2017 Vaibhav Malhotra. All rights reserved.
//
#include "GameWindow.hpp"
typedef struct
{
GLfloat positionCoordinates[3];
GLfloat textureCoordinates[2];
} vertexData;
#define Square_Size 100
vertexData vertices[] = {
{{0.0f,0.0f,0.0f}, {0.0f,0.0f}},
{{Square_Size,0.0f,0.0f},{1.0f,0.0f}},
{{Square_Size,Square_Size,0.0f},{1.0f,1.0f}},
{{0.0f,Square_Size,0.0f},{0.0f,1.0f}}
};
void GameWindow::setRunning(bool newRunning)
{
_running = newRunning;
}
bool GameWindow::getRunning()
{
return _running;
}
GLuint GameWindow::loadAndBufferImage(const char *filename)
{
GLFWimage imageData;
glfwReadImage(filename, &imageData, NULL);
GLuint textureBufferID;
glGenTextures(1, &textureBufferID);
glBindTexture(GL_TEXTURE_2D, textureBufferID);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageData.Width, imageData.Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageData.Data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glfwFreeImage(&imageData);
return textureBufferID;
}
GameWindow::GameWindow(bool running):_running(running),_height(800),_width(800*16/9),_vertexBufferID(0)
{
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glViewport(0.0f, 0.0f, _width, _height);
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glMatrixMode(GL_PROJECTION);
gluOrtho2D(0, _width, 0, _height);
glMatrixMode(GL_MODELVIEW);
glGenBuffers(1, &_vertexBufferID);
glBindBuffer(GL_ARRAY_BUFFER, _vertexBufferID);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FLOAT, sizeof(vertexData), (GLvoid *) offsetof(vertexData, positionCoordinates));
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(2, GL_FLOAT, sizeof(vertexData), (GLvoid *) offsetof(vertexData, textureCoordinates));
_textureBufferID = loadAndBufferImage("rocket.tga");
}
void GameWindow::render()
{
glClear(GL_COLOR_BUFFER_BIT);
//glColor3f(1.0f, 0.0f, 0.0f);
glDrawArrays(GL_QUADS, 0, 4);
glfwSwapBuffers();
}
void GameWindow::update()
{
}
Under the render function the code glDrawArrays(GL_QUADS, 0, 4); is returning a runtime error:
Thread 1: EXC_BAD_ACCESS (code=1, address=0x0).
For output I am just getting a black screen.
Why is this error is coming for me?

Answer 1

Under the render function the code glDrawArrays(GL_QUADS, 0, 4); is returning a runtime error Thread 1: EXC_BAD_ACCESS (code=1, address=0x0).
A memory access violation on glDrawArrays generally hints at some sort of problem with VBOs or similar storage objects.
From what I can tell, there are three issues with your code:
You are only calling glEnableClientState and its corresponding gl*Pointer calls once, when they need to be called every frame before glDrawArrays. If you'd like to only call them once, look into Vertex Array Objects (VAOs), although these are only available since OpenGL 3. Bear in mind, that when you move the glEnableClientState calls, you will have to ensure that your buffer is bound again with glBindBuffer.
Each client state has a corresponding gl*Pointer call. You correctly use glVertexPointer for GL_VERTEX_ARRAY, but for GL_TEXTURE_COORD_ARRAY, you need glTexCoordPointer.
Your glEnableClientState calls are missing their corresponding glDisableClientState calls, which need to be called in reverse order of the enabling calls, after your glDrawArrays call.
Just as a side note, the GLU library is deprecated. Your gluOrtho2D call appears to be the only instance where you depend on it, and it can be easily replaced with:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, _width, 0, _height, -1.0f, 1.0f);

Answer 2

You are getting an exception in glDrawArrays because it tries to read memory at address 0, which is what your code actually specifies.
GL's texture coordinate array pointer is initializez to NULL and no VBO. Since you use legacy GL, this will be interpreted as a client memory address. Now you enable GL_TEXCOORD_ARRAY but never actually set glTexCoordPointer, so it stays NULL:
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glVertexPointer(2, GL_FLOAT, sizeof(vertexData), (GLvoid *) offsetof(vertexData, textureCoordinates));
The quick solution is of course to not overwrite your vertex array pointer state by having it point to the the texture coords, but to specify the texcoord array pointer via glTexCoordPointer.
The real solution is to give up on legacy GL which is deprecated0 since a decade by now, and switch to "modern" OpenGL using a GL 3.2 core profile or above.