From 580b9f6bd513a4dab7527538c8e7aeca2daeaed6 Mon Sep 17 00:00:00 2001 From: Rcmaniac25 Date: Fri, 30 Jun 2017 23:21:40 +0000 Subject: [PATCH] Implemented pre-C99 support for macro expansion for callbacks. Note: not tested with a pre-C99 compiler as I (the author) don't have any compiler that doesn't C99. Fixed copyright too. git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1814 7f0cb862-5218-0410-a997-914c9d46530a --- src/fg_callback_macros.h | 82 +++++++++++++++++++++++++++++++++++++--------- 1 file changed, 67 insertions(+), 15 deletions(-) diff --git a/src/fg_callback_macros.h b/src/fg_callback_macros.h index a5fa7b5..2406243 100644 --- a/src/fg_callback_macros.h +++ b/src/fg_callback_macros.h @@ -3,9 +3,8 @@ * * The freeglut library callback macro file. * - * Copyright (c) 1999-2000 Pawel W. Olszta. All Rights Reserved. - * Written by Pawel W. Olszta, - * Creation date: Thu Dec 2 1999 + * Copyright (C) 2016 Vincent Simonetti + * Creation date: Sat Jan 16 2016 * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), @@ -38,20 +37,65 @@ * FG_COMPILER_SUPPORTS_VA_ARGS: if the compiler supports varadic macros */ +/* + * Info: + * + * This took a while to figure out, so be sure try to understand what is happening so that you can ensure that whatever you + * change won't break other areas. + * + * If you are just adding a new callback/changing it's argument count, just go to the bottom of the file. + * + * This whole file exists purely for the sake of preventing the need to implement additional parsing logic for each callback + * to pass user arguments. Of course, the necessity to support older compilers means that, as seen in the line above, there + * is still a requirement to add/modify code to handle callbacks. If freeglut ever requires newer compilers (at minimum, ones + * that support C99 or higher), code can very slowly be removed from this file. Even better would be if the C standard eventually + * supports something similar to what GCC has implemented or offers an alternative. Another option is if C++ would be "allowed" by + * project maintaners, as then templates can be used and function overloading. Ironically, the template would probably look worse + * then the GCC macro, so maybe it's good to stay as is. + * + * Onto the different "versions" of macros: + * + * There is one for GCC/Clang(/and supposedly the Intel compiler) which supports the non-standard ##__VA_ARGS__ token. The code may + * look ugly, but the result is, if this was standard, no one would ever need to open this file unless they were curious (or needed + * more then 5 arguments for a callback, but that's trivial to add). It works by adding many fake macros to a "picker" macro + * (PP_HAS_ARGS_IMPL2) which then indictaes which macro counter to use. As we can already use varadic macros (the VA in __VA_ARGS__), + * this just becomes a "reuse the arguments*. + * + * The next is for any non-GCC/Clang/etc. compiler *cough* MSVC/compiler you probably shouldn't be using *cough* that supports C99 + * by default. It requires each callback to have a specific argument count passthrough macro. The only reason there are specific + * count macros is so that (see paraghraph below) don't need have their own set of callback macros. Ideally, there would only be + * ZERO and ONE_OR_MORE. This works by having callback-specific macros call a specific handler macro to return user data (ZERO) or + * return one or more arguments along with userData (ONE_OR_MORE) where, with varadic macros, it just reuses the arguments. + * + * The last set is for the poor individual who has to use a compiler that doesn't support C99 by default, or may not support it at + * all. Stuff like MSVC6... It works by having a specific-count macro that "extracts" each argument to have them reused without the + * parathesis. + * + * A note on parathesis, as earlier mentioned, if the GCC varadic macro element was standard, then instead of needing: + * + * func EXPAND_WCB(Mouse)(( (GLUT_LEFT_BUTTON, GLUT_DOWN, 10, 30), userData)); + * + * ...you can do the following: + * + * func EXPAND_WCB (GLUT_LEFT_BUTTON, GLUT_DOWN, 10, 30); + * + * Wow... so much nice and easier to understand. Sub-note: I have not worked on a version that explicitly takes userData, so for now + * if you can get to that version, look in the version control change history for this file and you'll find that version which + * implicitly passes "userData" and only works on GCC vardiac macro supporting compilers. + */ + #ifdef FG_COMPILER_SUPPORTS_GCC_VA_ARGS_HACK /* * EXPAND_WCB() is used as: + * + * EXPAND_WCB( cbname )(( arg_list, userData )) + * + * ... where {(arg_list)} is the parameter list and userData is user + * provided data. * - * EXPAND_WCB arg_list - * - * ... where {(arg_list)} is the parameter list. - * - * This will take the arg_list and extend it by one argument, adding - * the argument "userData" to the end of the list. - * - * All additional args are to get around trailing ',', argument counts, - * and not needing a GCC extension to make this work. + * All additional macros are to get around trailing ',' for zero-arg + * callbacks. * * Modification of: * http://stackoverflow.com/questions/5355241/generating-function-declaration-using-a-macro-iteration/5355946#5355946 @@ -115,7 +159,6 @@ * #define EXPAND_WCB_SUB_Entry(args) EXPAND_WCB_ONE args */ -#define FG_COMPILER_SUPPORTS_VA_ARGS //XXX (should be compiler defined) #ifdef FG_COMPILER_SUPPORTS_VA_ARGS #define EXPAND_WCB_UNPARAN(...) __VA_ARGS__ @@ -129,8 +172,17 @@ #else -//TODO -#error "Compiler does not support varadic argument macros" +#define EXTRACT_ONE_ARGS(arg1) arg1 +#define EXTRACT_TWO_ARGS(arg1, arg2) arg1, arg2 +#define EXTRACT_THREE_ARGS(arg1, arg2, arg3) arg1, arg2, arg3 +#define EXTRACT_FOUR_ARGS(arg1, arg2, arg3, arg4) arg1, arg2, arg3, arg4 +#define EXTRACT_FIVE_ARGS(arg1, arg2, arg3, arg4, arg5) arg1, arg2, arg3, arg4, arg5 + +#define EXPAND_WCB_ONE(args, userData) (EXTRACT_ONE_ARGS args, userData) +#define EXPAND_WCB_TWO(args, userData) (EXTRACT_TWO_ARGS args, userData) +#define EXPAND_WCB_THREE(args, userData) (EXTRACT_THREE_ARGS args, userData) +#define EXPAND_WCB_FOUR(args, userData) (EXTRACT_FOUR_ARGS args, userData) +#define EXPAND_WCB_FIVE(args, userData) (EXTRACT_FIVE_ARGS args, userData) #endif -- 1.7.10.4