Hacky OpenGL function pointer queries. Only a subset of the API functions are loaded to save space.

gl_loader.cpp

#include "gl_loader.h" 
#define WIN32_LEAN_AND_MEAN 
#define WIN32_EXTRA_LEAN 
#include "Windows.h" 
#include "../logger.h" 
#include "../util.h" 

void *GetAnyGLFuncAddress(const char *name)
{
    void *p = (void *)wglGetProcAddress(name);
    if (p == 0 ||
        (p == (void*)0x1) || (p == (void*)0x2) || (p == (void*)0x3) ||
        (p == (void*)-1))
    {
        HMODULE module = LoadLibraryA("opengl32.dll");
        p = (void *)GetProcAddress(module, name);
    }

    return p;
}


const char* gl_function_names[] = { 
"glActiveTexture", 
"glDebugMessageCallbackAMD", 
"glDebugMessageEnableAMD", 
"glDebugMessageInsertAMD", 
"glGetDebugMessageLogAMD", 
"glDebugMessageCallback", 
"glDebugMessageControl", 
"glGetActiveUniformBlockName", 
"glGetActiveUniformBlockiv", 
"glGetActiveUniformsiv", 
"glGetActiveUniformName", 
"glCompileShader", 
"glGetShaderiv", 
"glGetShaderInfoLog", 
"glCreateProgram", 
"glProgramBinary", 
"glCreateShader", 
"glShaderSource", 
"glDeleteShader", 
"glGetProgramiv", 
"glAttachShader", 
"glProgramParameteri", 
"glLinkProgram", 
"glDeleteProgram", 
"glUseProgram", 
"glGetUniformLocation", 
"glGetUniformBlockIndex", 
"glGetProgramBinary", 
"glGenVertexArrays", 
"glBindVertexArray", 
"glEnableVertexAttribArray", 
"glGenBuffers", 
"glBindBuffer", 
"glBufferData", 
"glVertexAttribPointer", 
"glDeleteBuffers", 
"glDeleteVertexArrays", 
"glUniform1f", 
"glUniform3fv", 
"glUniform4fv", 
"glUniformMatrix4fv",
"glBindBufferBase",
"glDispatchCompute",
"glMemoryBarrier",
"glMultiDrawArrays",
"glDrawBuffers",
"glGenFramebuffers",
"glFramebufferTexture2D",
"glCheckFramebufferStatus",
"glBindFramebuffer",
"glDeleteFramebuffers",
"glGetQueryObjectiv",
"glGetQueryObjectui64v",
"glTexImage2DMultisample",
"glGenerateMipmap",
"glUniform1i",
"glGetAttribLocation",
"glBufferSubData",
"glUniform4iv"
}; 

void* gl_function_pointers[sizeof(gl_function_names)/sizeof(const char*)]; 

#ifdef DEBUG
const char* gl_debug_function_names[] = {
	"glGetTextureParameteriv",
	"glDetachShader",
	"glGenQueries",
	"glEndQuery",
	"glBeginQuery",
	"glGetProgramiv",
	"glMapBuffer",
	"glUnmapBuffer"
};
void* gl_debug_function_pointers[sizeof(gl_function_names)/sizeof(const char*)]; 
#endif
 
int load_gl_functions() {
    int failed = 0;
	for (int i = 0; i < sizeof(gl_function_names) / sizeof(const char*); i++) {
		const char* name = gl_function_names[i];
		void* ptr = GetAnyGLFuncAddress(name);
		gl_function_pointers[i] = ptr;
		if (ptr == NULL) {
#ifdef DEBUG
			trace("Failed to load GL func '%s'", name);
#endif
			failed++;
		}
	}

#ifdef DEBUG
	for (int i = 0; i < sizeof(gl_debug_function_names) / sizeof(const char*); i++) {
		const char* name = gl_debug_function_names[i];
		void* ptr = GetAnyGLFuncAddress(name);
		gl_debug_function_pointers[i] = ptr;
		if (ptr == NULL) {
			trace("Failed to load debug GL func '%s'", name);
			failed++;
		}
	}
#endif

    return failed;
}

gl_loader.h

#pragma once 
extern void* gl_function_pointers[]; 
/* Returns the number of functions that failed to load. */ 
int load_gl_functions(); 
 
#define glActiveTexture ((PFNGLACTIVETEXTUREPROC)gl_function_pointers[0]) 
#define glDebugMessageCallbackAMD ((PFNGLDEBUGMESSAGECALLBACKAMDPROC)gl_function_pointers[1]) 
#define glDebugMessageEnableAMD ((PFNGLDEBUGMESSAGEENABLEAMDPROC)gl_function_pointers[2]) 
#define glDebugMessageInsertAMD ((PFNGLDEBUGMESSAGEINSERTAMDPROC)gl_function_pointers[3]) 
#define glGetDebugMessageLogAMD ((PFNGLGETDEBUGMESSAGELOGAMDPROC)gl_function_pointers[4]) 
#define glDebugMessageCallback ((PFNGLDEBUGMESSAGECALLBACKPROC)gl_function_pointers[5]) 
#define glDebugMessageControl ((PFNGLDEBUGMESSAGECONTROLPROC)gl_function_pointers[6]) 
#define glGetActiveUniformBlockName ((PFNGLGETACTIVEUNIFORMBLOCKNAMEPROC)gl_function_pointers[7]) 
#define glGetActiveUniformBlockiv ((PFNGLGETACTIVEUNIFORMBLOCKIVPROC)gl_function_pointers[8]) 
#define glGetActiveUniformsiv ((PFNGLGETACTIVEUNIFORMSIVPROC)gl_function_pointers[9]) 
#define glGetActiveUniformName ((PFNGLGETACTIVEUNIFORMNAMEPROC)gl_function_pointers[10]) 
#define glCompileShader ((PFNGLCOMPILESHADERPROC)gl_function_pointers[11]) 
#define glGetShaderiv ((PFNGLGETSHADERIVPROC)gl_function_pointers[12]) 
#define glGetShaderInfoLog ((PFNGLGETSHADERINFOLOGPROC)gl_function_pointers[13]) 
#define glCreateProgram ((PFNGLCREATEPROGRAMPROC)gl_function_pointers[14]) 
#define glProgramBinary ((PFNGLPROGRAMBINARYPROC)gl_function_pointers[15]) 
#define glCreateShader ((PFNGLCREATESHADERPROC)gl_function_pointers[16]) 
#define glShaderSource ((PFNGLSHADERSOURCEPROC)gl_function_pointers[17]) 
#define glDeleteShader ((PFNGLDELETESHADERPROC)gl_function_pointers[18]) 
#define glGetProgramiv ((PFNGLGETPROGRAMIVPROC)gl_function_pointers[19]) 
#define glAttachShader ((PFNGLATTACHSHADERPROC)gl_function_pointers[20]) 
#define glProgramParameteri ((PFNGLPROGRAMPARAMETERIPROC)gl_function_pointers[21]) 
#define glLinkProgram ((PFNGLLINKPROGRAMPROC)gl_function_pointers[22]) 
#define glDeleteProgram ((PFNGLDELETEPROGRAMPROC)gl_function_pointers[23]) 
#define glUseProgram ((PFNGLUSEPROGRAMPROC)gl_function_pointers[24]) 
#define glGetUniformLocation ((PFNGLGETUNIFORMLOCATIONPROC)gl_function_pointers[25]) 
#define glGetUniformBlockIndex ((PFNGLGETUNIFORMBLOCKINDEXPROC)gl_function_pointers[26]) 
#define glGetProgramBinary ((PFNGLGETPROGRAMBINARYPROC)gl_function_pointers[27]) 
#define glGenVertexArrays ((PFNGLGENVERTEXARRAYSPROC)gl_function_pointers[28]) 
#define glBindVertexArray ((PFNGLBINDVERTEXARRAYPROC)gl_function_pointers[29]) 
#define glEnableVertexAttribArray ((PFNGLENABLEVERTEXATTRIBARRAYPROC)gl_function_pointers[30]) 
#define glGenBuffers ((PFNGLGENBUFFERSPROC)gl_function_pointers[31]) 
#define glBindBuffer ((PFNGLBINDBUFFERPROC)gl_function_pointers[32]) 
#define glBufferData ((PFNGLBUFFERDATAPROC)gl_function_pointers[33]) 
#define glVertexAttribPointer ((PFNGLVERTEXATTRIBPOINTERPROC)gl_function_pointers[34]) 
#define glDeleteBuffers ((PFNGLDELETEBUFFERSPROC)gl_function_pointers[35]) 
#define glDeleteVertexArrays ((PFNGLDELETEVERTEXARRAYSPROC)gl_function_pointers[36]) 
#define glUniform1f ((PFNGLUNIFORM1FPROC)gl_function_pointers[37]) 
#define glUniform3fv ((PFNGLUNIFORM3FVPROC)gl_function_pointers[38]) 
#define glUniform4fv ((PFNGLUNIFORM4FVPROC)gl_function_pointers[39]) 
#define glUniformMatrix4fv ((PFNGLUNIFORMMATRIX4FVPROC)gl_function_pointers[40]) 
#define glBindBufferBase ((PFNGLBINDBUFFERBASEPROC)gl_function_pointers[41]) 
#define glDispatchCompute ((PFNGLDISPATCHCOMPUTEPROC)gl_function_pointers[42]) 
#define glMemoryBarrier ((PFNGLMEMORYBARRIERPROC)gl_function_pointers[43]) 
#define glMultiDrawArrays ((PFNGLMULTIDRAWARRAYSPROC)gl_function_pointers[44]) 
#define glDrawBuffers ((PFNGLDRAWBUFFERSPROC)gl_function_pointers[45]) 
#define glGenFramebuffers ((PFNGLGENFRAMEBUFFERSPROC)gl_function_pointers[46]) 
#define glFramebufferTexture2D ((PFNGLFRAMEBUFFERTEXTURE2DPROC)gl_function_pointers[47]) 
#define glCheckFramebufferStatus ((PFNGLCHECKFRAMEBUFFERSTATUSPROC)gl_function_pointers[48]) 
#define glBindFramebuffer ((PFNGLBINDFRAMEBUFFERPROC)gl_function_pointers[49]) 
#define glDeleteFramebuffers ((PFNGLDELETEFRAMEBUFFERSPROC)gl_function_pointers[50]) 
#define glGetQueryObjectiv ((PFNGLGETQUERYOBJECTIVPROC)gl_function_pointers[51]) 
#define glGetQueryObjectui64v ((PFNGLGETQUERYOBJECTUI64VPROC)gl_function_pointers[52]) 
#define glTexImage2DMultisample ((PFNGLTEXIMAGE2DMULTISAMPLEPROC)gl_function_pointers[53]) 
#define glGenerateMipmap ((PFNGLGENERATEMIPMAPPROC)gl_function_pointers[54]) 
#define glUniform1i ((PFNGLUNIFORM1IPROC)gl_function_pointers[55]) 
#define glGetAttribLocation ((PFNGLGETATTRIBLOCATIONPROC)gl_function_pointers[56]) 
#define glBufferSubData ((PFNGLBUFFERSUBDATAPROC)gl_function_pointers[57]) 
#define glUniform4iv ((PFNGLUNIFORM4IVPROC)gl_function_pointers[58]) 

#ifdef DEBUG
extern void* gl_debug_function_pointers[]; 
#define glGetTextureParameteriv ((PFNGLGETTEXTUREPARAMETERIVPROC)gl_debug_function_pointers[0]) 
#define glDetachShader ((PFNGLDETACHSHADERPROC)gl_debug_function_pointers[1]) 
#define glGenQueries ((PFNGLGENQUERIESPROC)gl_debug_function_pointers[2]) 
#define glEndQuery ((PFNGLENDQUERYPROC)gl_debug_function_pointers[3]) 
#define glBeginQuery ((PFNGLBEGINQUERYPROC)gl_debug_function_pointers[4]) 
#define glGetProgramiv ((PFNGLGETPROGRAMIVPROC)gl_debug_function_pointers[5]) 
#define glMapBuffer ((PFNGLMAPBUFFERPROC)gl_debug_function_pointers[6]) 
#define glUnmapBuffer ((PFNGLUNMAPBUFFERPROC)gl_debug_function_pointers[7]) 
#endif