调用 glGetString 时出现访问冲突错误

Question

我正在使用 SDL2 + GLAD 在 C++ 中创建一个 OpenGL 应用程序。在我的主要功能中，我有以下代码：

#include <iostream>
#include <SDL.h>

#include <glad\glad.h>

int main(int argc, char *argv[]) {
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        std::cout << "SDL could not be initialized.";
        return 1;
    }

    SDL_GL_LoadLibrary(nullptr);

    SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 4);

    SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 5);

    SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
    SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

    SDL_Window *window = SDL_CreateWindow("Hello world", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 500, 500, SDL_WINDOW_OPENGL);

    if (window == nullptr) {
        std::cout << "SDL could not open window";
        return 1;
    }

    const SDL_GLContext context = SDL_GL_CreateContext(window);

    if (context == nullptr) {
        std::cout << "SDL could not create context";
        return 1;
    }

    printf("OpenGL loaded\n");

    printf("Vendor:          %s\n", glGetString(GL_VENDOR));
    printf("Renderer:        %s\n", glGetString(GL_RENDERER));
    printf("Version OpenGL:  %s\n", glGetString(GL_VERSION));
    printf("Version GLSL:    %s\n", glGetString(GL_SHADING_LANGUAGE_VERSION));

    glDisable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);

    int w, h;
    SDL_GetWindowSize(window, &w, &h);
    glViewport(0, 0, w, h);
    glClearColor(0.0f, 0.5f, 1.0f, 0.0f);

    SDL_Event event;
    bool quit = false;
    while (!quit) {
        SDL_GL_SwapWindow(window);
        while (SDL_PollEvent(&event)) {
            if (event.type == SDL_QUIT) {
                quit = true;
            }
        }
    }

    return 0;
}

但是，当我运行这样做时，我收到以下错误：

Exception thrown at 0x0000000000000000 in TestApp.exe: 0xC0000005: Access violation executing location 0x0000000000000000.

打印了 OpenGL loaded 消息，Visual Sutio 显示在 printf("Vendor:%s\n", glGetString(GL_VENDOR)); 行抛出错误。

我已确保 link SDL2 和 GLAD 在解决方案的属性 window 中正确。什么可能导致此错误？

Answer 1

如果产生错误，glGetString returns 0。然后 printf 尝试访问地址 0 处的内存。或者 glGetString 不可用，因为未加载 OpenGL 库。所以您可能在初始化 OpenGL 时遇到了一些问题。尝试在 SDL_GL_LoadLibrary

中指定 OpenGL DLL 模块的完整路径

请确保SDL_GL_LoadLibrary为return 0，否则请致电SDL_GetError()获取更多信息。

Answer 2

Glad Loader-Generator has to be initialized by either gladLoadGL or gladLoadGLLoader, right after creating and making current the OpenGL context by SDL_GL_CreateContext.

另见 OpenGL Loading Library - glad

例如：

const SDL_GLContext context = SDL_GL_CreateContext(window);
if (context == nullptr) {
    std::cout << "SDL could not create context";
    return 1;
}

if (!gladLoadGLLoader((GLADloadproc)SDL_GL_GetProcAddress))
{
    std::cout << "Failed to initialize OpenGL context" << std::endl;
    return -1;
}

printf("OpenGL loaded\n");

printf("Vendor:          %s\n", glGetString(GL_VENDOR));
printf("Renderer:        %s\n", glGetString(GL_RENDERER));
printf("Version OpenGL:  %s\n", glGetString(GL_VERSION));
printf("Version GLSL:    %s\n", glGetString(GL_SHADING_LANGUAGE_VERSION));

调用 glGetString 时出现访问冲突错误

Access violation error when calling glGetString

c++

opengl

sdl-2

glad