I am writing a game engine in C and OpenGL and when I open my first test window i receive this issue:

Segmentation fault (core dumped)

There is no error when compiling, and it compiles just fine. The problem lies when I go to open the window.

HOW TO REPRODUCE:

#include <glad/glad.h>
#include <GLFW/glfw3.h>
#include <iostream>

void framebuffer_size_callback(GLFWwindow* window, int width, int height);

void framebuffer_size_callback(GLFWwindow* window, int width, int height)
{
    glViewport(0, 0, width, height);
}

int main()
{
  typedef void (*GL_GENBUFFERS) (GLsizei, GLuint*);
  GL_GENBUFFERS glGenBuffers = (GL_GENBUFFERS) glfwGetProcAddress("glGenBuffers");
  unsigned int buffer;
  glGenBuffers(1, &buffer);

  glfwInit();
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  GLFWwindow* window = glfwCreateWindow(800, 600, "BloodBunny", NULL, NULL);
  if (window == NULL)
  {
    std::cout << "Failed to create GLFW window" << std::endl;
    glfwTerminate();
    return -1;
  }
  glfwMakeContextCurrent(window);
  if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress))
  {
    std::cout << "Failed to initialize GLAD" << std::endl;
    return -1;
  }
  while(!glfwWindowShouldClose(window))
  {
    glfwSwapBuffers(window);
    glfwPollEvents();
  }
  glfwSetFramebufferSizeCallback(window, framebuffer_size_callback);
  glViewport(0,0,800,600);
  glfwTerminate();
  return 0;
}

CodePudding user response：

glfwGetProcAddress() will only (potentially, depending on the name requested and the GL version of the current context) return usable, non-NULL function-pointers if a GL context is current.

With GLFW you make a window's context current via glfwMakeContextCurrent() so if you truly want to grab your own pointer to glGenBuffers() you need to move the glfwGetProcAddress() call to after a successful glfwMakeContextCurrent():

...
glfwMakeContextCurrent(window);
...
typedef void (*GL_GENBUFFERS) (GLsizei, GLuint*);
GL_GENBUFFERS glGenBuffers = (GL_GENBUFFERS) glfwGetProcAddress("glGenBuffers");
unsigned int buffer;
glGenBuffers(1, &buffer);
...

...though honestly there's little point since you're calling gladLoadGLLoader() right after glfwMakeContextCurrent() which will populate a perfectly usable glGenBuffers() pointer at global scope all on its own.