Seg fault while calling glfwSwapBuffers

Question

在ArchLinux, DWM(完全更新和打补丁)上使用GLFW和OpenGL时，我似乎有一个segfault。

我回溯了代码，它在glfwSwapBuffers(window)中有segFault。

下面是我的代码:

main.cpp

#include <iostream>
#include "gui/window.h"
int main(int, char**) {
Window window("Test GL", 800, 600);
if(!window.hasCorrectlyLoaded()) {
return 1;
}
while (!window.shouldClose())
{
glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
window.pollEvents();
}
}

window.h

#ifndef __WINDOW_H__
#define __WINDOW_H__
#include <string>
#include <glad/gl.h>
#include <GLFW/glfw3.h>
class Window {
private:
GLFWwindow *window;
bool correctlyLoaded;
public:
Window(const std::string&, int, int);
~Window();
const bool hasCorrectlyLoaded();
const bool shouldClose();
const void pollEvents();
};
#endif // __WINDOW_H__

window.cpp

#include "window.h"
#include <spdlog/spdlog.h>
Window::Window(const std::string& title, int width, int height)
{
correctlyLoaded = false;
if(!glfwInit()) {
spdlog::default_logger()->critical("Could not load GLFW");
return;
}
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
GLFWwindow* window = glfwCreateWindow(width, height, title.c_str(), nullptr, nullptr);
if (!window)
{
spdlog::default_logger()->critical("Failed to create GLFW window !");
return;
}
glfwMakeContextCurrent(window);
if (!gladLoadGL(glfwGetProcAddress))
{
spdlog::default_logger()->critical("Failed to load OpenGL !");
return;
}
spdlog::default_logger()->info("Loaded OpenGL {}", glfwGetVersionString());

glViewport(0, 0, width, height);
correctlyLoaded = true;
}
const void Window::pollEvents()
{
glfwSwapBuffers(window);
glfwPollEvents(); //<- Seg fault here
}
Window::~Window()
{
glfwTerminate();
}
const bool Window::hasCorrectlyLoaded()
{
return correctlyLoaded;
}
const bool Window::shouldClose()
{
return glfwWindowShouldClose(window);
}

在进一步研究的同时，我偶然发现了一个答案，告诉我设置glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_API)窗口提示，但我仍然得到了一个段错误，但在不同的地方:

GLFW源代码

GLFWAPI void glfwSwapBuffers(GLFWwindow* handle)
{
_GLFWwindow* window = (_GLFWwindow*) handle;
assert(window != NULL);
_GLFW_REQUIRE_INIT();
if (window->context.client == GLFW_NO_API)
{
_glfwInputError(GLFW_NO_WINDOW_CONTEXT,
"Cannot swap buffers of a window that has no OpenGL or OpenGL ES context"); //<- Seg fault without window hint
return;
}
window->context.swapBuffers(window); //<- Seg fault with window hint
}

下面是我从日志记录中得到的输出:

[2022-05-24 20:01:04.252] [info] Loaded OpenGL 3.4.0 X11 GLX Null EGL OSMesa monotonic
[1]    432406 segmentation fault (core dumped)  /home/lygaen/code/testgl/build/testgl

Answer 1

您的问题发生在windows .cpp中，在这一行:

//...
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
GLFWwindow* window = glfwCreateWindow(width, height, title.c_str(), nullptr, nullptr); //<---
if (!window)
{
//...

您已经将window重新声明为此构造函数的局部变量，因此，指针永远不会转义构造函数，并且悬空。

在尝试分配类成员时，一个好习惯是使用this关键字。这通常是多余的，但它确实有助于表明意图。所以代码应该改成这样:

//...
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GLFW_TRUE);
this->window = glfwCreateWindow(width, height, title.c_str(), nullptr, nullptr); //<---
if (!this->window)
{
//...

如果你的样式指南不允许，你可以省略this->;唯一重要的部分是，您没有声明一个完全新的变量来遮蔽类成员。