OpenGL：wglGetProcAddress始终返回NULL

Question

I am trying to create an OpenGL program which uses shaders. I tried using the following code to load the shader functions, but wglGetProcAddress always returns 0 no matter what I do. The rest of the program works as normal when not using the shader functions.

HDC g_hdc;
HGLRC g_hrc;

PFNGLATTACHSHADERPROC   glpf_attachshader;
PFNGLCOMPILESHADERPROC  glpf_compileshader;
PFNGLCREATEPROGRAMPROC  glpf_createprogram;
PFNGLCREATESHADERPROC   glpf_createshader;
PFNGLDELETEPROGRAMPROC  glpf_deleteprogram;
PFNGLDELETESHADERPROC   glpf_deleteshader;
PFNGLDETACHSHADERPROC   glpf_detachshader;
PFNGLLINKPROGRAMPROC    glpf_linkprogram;
PFNGLSHADERSOURCEPROC   glpf_shadersource;
PFNGLUSEPROGRAMPROC     glpf_useprogram;

void GL_Init(HDC dc)
{
    //create pixel format
    PIXELFORMATDESCRIPTOR pfd = 
    {
        sizeof(PIXELFORMATDESCRIPTOR), 
        1,
        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER, 
        PFD_TYPE_RGBA, 
        32,
        0, 0, 0, 0, 0, 0,
        0, 0, 0,
        0, 0, 0, 0,
        32, 0, 0,
        PFD_MAIN_PLANE,
        0, 0, 0, 0
    };

    //choose + set pixel format
    int pixfmt = ChoosePixelFormat(dc, &pfd);
    if (pixfmt && SetPixelFormat(dc, pixfmt, &pfd))
    {
        //create GL render context
        if (g_hrc = wglCreateContext(dc))
        {
            g_hdc = dc;

            //select GL render context
            wglMakeCurrent(dc, g_hrc);

            //get function pointers     
            glpf_attachshader   = (PFNGLATTACHSHADERPROC)   wglGetProcAddress("glAttachShader");
            glpf_compileshader  = (PFNGLCOMPILESHADERPROC)  wglGetProcAddress("glCompileShader");
            glpf_createprogram  = (PFNGLCREATEPROGRAMPROC)  wglGetProcAddress("glCreateProgram");
            glpf_createshader   = (PFNGLCREATESHADERPROC)   wglGetProcAddress("glCreateShader");
            glpf_deleteprogram  = (PFNGLDELETEPROGRAMPROC)  wglGetProcAddress("glDeleteProgram");
            glpf_deleteshader   = (PFNGLDELETESHADERPROC)   wglGetProcAddress("glDeleteShader");
            glpf_detachshader   = (PFNGLDETACHSHADERPROC)   wglGetProcAddress("glDetachShader");
            glpf_linkprogram    = (PFNGLLINKPROGRAMPROC)    wglGetProcAddress("glLinkProgram");
            glpf_shadersource   = (PFNGLSHADERSOURCEPROC)   wglGetProcAddress("glShaderSource");
            glpf_useprogram     = (PFNGLUSEPROGRAMPROC)     wglGetProcAddress("glUseProgram");
        }
    }
}

I know this may be a possible duplicate, but on most of the other posts the error was because of simple mistakes (like calling wglGetProcAddress before wglMakeCurrent ). I'm in a bit of an unique situation - any help would be appreciated.

Answer 1

You are requesting a 32-bit Z-Buffer in this code. That will probably throw you onto the GDI software rasterizer (which implements exactly 0 extensions). You can use 32-bit depth buffers on modern hardware, but most of the time you cannot do it using the default framebuffer, you have to use FBOs.

I have seen some drivers accept 32-bit depth only to fallback to the closest matching 24-bit pixel format, while others simply refuse to give a hardware pixel format at all (this is probably your case). If this is in fact your problem, a quick investigation of your GL strings ( GL_RENDERER , GL_VERSION , GL_VENDOR ) should make it obvious.

24-bit Depth + 8-bit Stencil is pretty much universally supported, this is the first depth/stencil size you should try.

Answer 2

You could use glew to do that kind of work for you. Or maybe you don't want?

EDIT: You could maybe use glext.h then. Or at least look in it and copy paste what interest you.

I'm not an expert I just remember having that kind of problem and try to remind what was conected to it.