OpenGL 1.0 loader in Win32

ogl_load.c

static const char *const GL_funcnames[] = {
    "wglDeleteContext",
    "wglUseFontBitmapsA",
    "wglSwapIntervalEXT",
    "glGetError",
    "glBlendFunc",
    "glEnable",
    "glDisable",
    "glViewport",
    "glVertex3f",
    "glClearColor",
    "glClear",
    "glBegin",
    "glColor4f",
    "glEnd",
    "glTexCoord2f",
    "glTexImage2D",
    "glGenTextures",
    "glBindTexture",
    "glTexParameteri",
    "glEnableClientState",
    "glDisableClientState",
    "glDrawArrays",
    "glVertexPointer",
};
struct {
    void *(*wglGetProcAddress)(const char *name);
    void *(*wglCreateContext)(void *hdc);
    int (*wglMakeCurrent)(void *hdc, void *hglrc);
    
    union {
        struct {
            
            int (*wglDeleteContext)(void *hglrc);
            int (*wglUseFontBitmapsA)(void *hdc, unsigned int, unsigned int, unsigned int);
            int (*wglSwapIntervalEXT)(int interval);
            unsigned int (*GetError)(void);
            void (*BlendFunc)(unsigned int sfactor, unsigned int dfactor);
            void (*Enable)(unsigned int cap);
            void (*Disable)(unsigned int cap);
            void (*Viewport)(int x, int y, int w, int h);
            void (*Vertex3f)(float x, float y, float z);
            void (*ClearColor)(float r, float g, float b, float a);
            void (*Clear)(unsigned int mask);
            void (*Begin)(unsigned int mode);
            void (*Color4f)(float r, float g, float b, float a);
            void (*End)(void);
            void (*TexCoord2f)(float s, float t);
            void (*TexImage2D)(unsigned int target, int level, int internalformat, int width, int height, int border, unsigned int format, unsigned int type, const void *pixels);
            void (*GenTextures)(int n, unsigned int *textures);
            void (*BindTexture)(unsigned int target, unsigned int texture);
            void (*TexParameteri)(unsigned int target, unsigned int pname, int param);
            void (*EnableClientState)(unsigned int cap);
            void (*DisableClientState)(unsigned int cap);
            void (*DrawArrays)(unsigned int mode, int first, int count);
            void (*VertexPointer)(int size, unsigned int type, int stride, const void *pointer);
            
        };
        enum { GL_NUM_FUNCTIONS = sizeof GL_funcnames / sizeof *GL_funcnames } dummy_enum;
        void *addresses[GL_NUM_FUNCTIONS];
    };
} GL;
static void *GL_load_proc(void *opengl32_dll, const char *name) {
    void *result = GL.wglGetProcAddress(name);
    if (!result) result = GetProcAddress(opengl32_dll, name);
    return result;
}
static int GL_load_procedures(void *opengl32_dll) {
    for (int i = 0; i < GL_NUM_FUNCTIONS; i += 1) {
        GL.addresses[i] = GL_load_proc(opengl32_dll, GL_funcnames[i]);
    }
    return 0;
}

// .. somewhere in startup:
void *opengl32_dll = LoadLibraryA("opengl32.dll");
*(void **)&GL.wglGetProcAddress = GetProcAddress(opengl32_dll, "wglGetProcAddress");
*(void **)&GL.wglCreateContext = GetProcAddress(opengl32_dll, "wglCreateContext");
*(void **)&GL.wglMakeCurrent = GetProcAddress(opengl32_dll, "wglMakeCurrent");
void *hglrc = GL.wglCreateContext(hdc);
GL.wglMakeCurrent(hdc, hglrc);
GL_load_procedures(opengl32_dll);