Added OPT macro to determine whether C++20's __VA_OPT__ is supported or not. Updated the undocumented variadic IS_EMPTY to use the functionality of __VA_OPT__ if it exists to provide perfect functionality for testing for emptiness.

include/boost/preprocessor/facilities/is_empty_variadic.hpp

@@ -16,6 +16,20 @@
 #
 # if BOOST_PP_VARIADICS
 #
+# include <boost/preprocessor/variadic/opt.hpp>
+#
+# if BOOST_PP_VARIADIC_OPT()
+#
+#define BOOST_PP_IS_EMPTY_FUNCTION2(...) \
+    __VA_OPT__(0,) 1 \
+/**/
+#define BOOST_PP_IS_EMPTY_FUNCTION(...) \
+    BOOST_PP_IS_EMPTY_FUNCTION2(__VA_ARGS__) \
+/**/
+#define BOOST_PP_IS_EMPTY(...) \
+    BOOST_PP_VARIADIC_OPT_ELEM0(BOOST_PP_IS_EMPTY_FUNCTION(__VA_ARGS__),) \
+/**/
+# else
 # include <boost/preprocessor/punctuation/is_begin_parens.hpp>
 # include <boost/preprocessor/facilities/detail/is_empty.hpp>
 #
@@ -53,5 +67,6 @@
 /**/
 #define BOOST_PP_IS_EMPTY_ZERO(...) 0
 # endif /* BOOST_PP_VARIADICS_MSVC && _MSC_VER <= 1400 */
+# endif /* BOOST_PP_VARIADIC_OPT() */
 # endif /* BOOST_PP_VARIADICS */
 # endif /* BOOST_PREPROCESSOR_FACILITIES_IS_EMPTY_VARIADIC_HPP */

include/boost/preprocessor/variadic/detail/opt.hpp

@@ -0,0 +1,30 @@
+# /* **************************************************************************
+#  *                                                                          *
+#  *     (C) Copyright Edward Diener 2019.                                    *
+#  *     Distributed under the Boost Software License, Version 1.0. (See      *
+#  *     accompanying file LICENSE_1_0.txt or copy at                         *
+#  *     http://www.boost.org/LICENSE_1_0.txt)                                *
+#  *                                                                          *
+#  ************************************************************************** */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_PREPROCESSOR_VARIADIC_DETAIL_OPT_HPP
+# define BOOST_PREPROCESSOR_VARIADIC_DETAIL_OPT_HPP
+#
+# include <boost/preprocessor/config/config.hpp>
+#
+# if BOOST_PP_VARIADICS && defined(__cplusplus) && __cplusplus > 201703L
+#
+# define BOOST_PP_VARIADIC_OPT_FUNCTION(...) \
+    __VA_OPT__(0,) 0, 0, 1 \
+/**/
+#
+# define BOOST_PP_VARIADIC_OPT_ELEM0(e0, ...) BOOST_PP_VARIADIC_OPT_ELEM_0(e0,__VA_ARGS__)
+# define BOOST_PP_VARIADIC_OPT_ELEM2(e0, ...) BOOST_PP_VARIADIC_OPT_ELEM_2(e0,__VA_ARGS__)
+# define BOOST_PP_VARIADIC_OPT_ELEM_0(e0, ...) e0
+# define BOOST_PP_VARIADIC_OPT_ELEM_2(e0, e1, e2, ...) e2
+#
+# endif
+#
+# endif

include/boost/preprocessor/variadic/opt.hpp

@@ -0,0 +1,28 @@
+# /* **************************************************************************
+#  *                                                                          *
+#  *     (C) Copyright Edward Diener 2019.                                    *
+#  *     Distributed under the Boost Software License, Version 1.0. (See      *
+#  *     accompanying file LICENSE_1_0.txt or copy at                         *
+#  *     http://www.boost.org/LICENSE_1_0.txt)                                *
+#  *                                                                          *
+#  ************************************************************************** */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_PREPROCESSOR_VARIADIC_OPT_HPP
+# define BOOST_PREPROCESSOR_VARIADIC_OPT_HPP
+#
+# include <boost/preprocessor/config/config.hpp>
+#
+# /* BOOST_PP_VARIADIC_OPT */
+#
+# if BOOST_PP_VARIADICS && defined(__cplusplus) && __cplusplus > 201703L
+# include <boost/preprocessor/variadic/detail/opt.hpp>
+# define BOOST_PP_VARIADIC_OPT() \
+  BOOST_PP_VARIADIC_OPT_ELEM2(BOOST_PP_VARIADIC_OPT_FUNCTION(),) \
+/**/
+# else
+# define BOOST_PP_VARIADIC_OPT() 0
+# endif
+#
+# endif

test/clang_cuda.cu

@@ -9,10 +9,7 @@
 #
 # /* See http://www.boost.org for most recent version. */
 #
-# include <boost/preprocessor/cat.hpp>
+# include <libs/preprocessor/test/test_macro.h>
-#
-# define BEGIN typedef int BOOST_PP_CAT(test_, __LINE__)[((
-# define END )==1) ? 1 : -1];
 
 #if defined(__clang__) && defined(__CUDACC__) && defined(__CUDA__)
 

test/config_info.cpp

@@ -13,6 +13,7 @@
 #include <iomanip>
 #include <string.h>
 #include <boost/preprocessor/stringize.hpp>
+#include <boost/preprocessor/variadic/opt.hpp>
 
 static unsigned int indent = 4;
 static unsigned int width = 40;
@@ -93,6 +94,8 @@ void print_macros()
   PRINT_MACRO(BOOST_PP_CONFIG_FLAGS());
   PRINT_MACRO(BOOST_PP_VARIADICS);
   PRINT_MACRO(BOOST_PP_VARIADICS_MSVC);
+  PRINT_MACRO(BOOST_PP_VARIADICS_MSVC);
+  PRINT_MACRO(BOOST_PP_VARIADIC_OPT());
 }
 
 int main()

test/isempty.cxx

@@ -38,7 +38,20 @@
 
 #if BOOST_PP_VARIADICS
 
-#if BOOST_PP_VARIADICS_MSVC /* Testing the VC++ variadic version */
+# include <boost/preprocessor/variadic/opt.hpp>
+
+#if defined(__cplusplus) && __cplusplus > 201703L && BOOST_PP_VARIADIC_OPT()
+
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN2) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN3) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN4) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN5) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN8) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN9) == 0 END
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN10) == 0 END
+
+#elif BOOST_PP_VARIADICS_MSVC /* Testing the VC++ variadic version */
 
 /* INCORRECT */
 

test/isempty_variadic_standard_failure.cxx

@@ -15,9 +15,19 @@
 #if BOOST_PP_VARIADICS && (BOOST_PP_CONFIG_FLAGS() & BOOST_PP_CONFIG_STRICT()) && !BOOST_PP_VARIADICS_MSVC
 
 #define FUNC_GEN8(x,y) (1,2,3)
+
+#if defined(__cplusplus) && __cplusplus > 201703L
   
+# include <boost/preprocessor/variadic/opt.hpp>
+
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN8) == BOOST_PP_VARIADIC_OPT() END
+
+#else
+
 BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN8) == 0 END
 
+#endif
+
 #else
   
 BEGIN 1 == 0 END

test/isempty_variadic_standard_failure2.cxx

@@ -16,8 +16,18 @@
 
 #define FUNC_GEN9(x,y,z) anything
   
+#if defined(__cplusplus) && __cplusplus > 201703L
+  
+# include <boost/preprocessor/variadic/opt.hpp>
+
+BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN9) == BOOST_PP_VARIADIC_OPT() END
+
+#else
+
 BEGIN BOOST_PP_IS_EMPTY(FUNC_GEN9) == 0 END
 
+#endif
+
 #else
   
 BEGIN 1 == 0 END

test/test.h

@@ -14,24 +14,7 @@
 # ifndef BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_H
 # define BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_H
 #
-# include <boost/preprocessor/cat.hpp>
+# include <libs/preprocessor/test/test_macro.h>
+# include <libs/preprocessor/test/test_main.h>
 #
-# define BEGIN typedef int BOOST_PP_CAT(test_, __LINE__)[((
-# define END )==1) ? 1 : -1];
-
-#if defined(__cplusplus)
-#include <cstdio>
-#if !defined(_STLP_MSVC) || _STLP_MSVC >= 1300
-namespace std { }
-using namespace std;
-#endif
-#else
-#include <stdio.h>
-#endif
-
-int main(void) {
-    printf("pass " __TIME__);
-    return 0;
-}
-
 # endif

test/test_macro.h

@@ -0,0 +1,22 @@
+# /* Copyright (C) 2001
+#  * Housemarque Oy
+#  * http://www.housemarque.com
+#  *
+#  * Distributed under the Boost Software License, Version 1.0. (See
+#  * accompanying file LICENSE_1_0.txt or copy at
+#  * http://www.boost.org/LICENSE_1_0.txt)
+#  */
+#
+# /* Revised by Paul Mensonides (2002) */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_MACRO_H
+# define BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_MACRO_H
+#
+# include <boost/preprocessor/cat.hpp>
+#
+# define BEGIN typedef int BOOST_PP_CAT(test_, __LINE__)[((
+# define END )==1) ? 1 : -1];
+#
+# endif

test/test_main.h

@@ -0,0 +1,32 @@
+# /* Copyright (C) 2001
+#  * Housemarque Oy
+#  * http://www.housemarque.com
+#  *
+#  * Distributed under the Boost Software License, Version 1.0. (See
+#  * accompanying file LICENSE_1_0.txt or copy at
+#  * http://www.boost.org/LICENSE_1_0.txt)
+#  */
+#
+# /* Revised by Paul Mensonides (2002) */
+#
+# /* See http://www.boost.org for most recent version. */
+#
+# ifndef BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_MAIN_H
+# define BOOST_LIBS_PREPROCESSOR_REGRESSION_TEST_MAIN_H
+#
+#if defined(__cplusplus)
+#include <cstdio>
+#if !defined(_STLP_MSVC) || _STLP_MSVC >= 1300
+namespace std { }
+using namespace std;
+#endif
+#else
+#include <stdio.h>
+#endif
+
+int main(void) {
+    printf("pass " __TIME__);
+    return 0;
+}
+
+# endif