Use C++20

configure.ac

@@ -70,15 +70,15 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ ]])],
 )
 CXXFLAGS="$old_CXXFLAGS $fast_math"
 
-# -std=c++14
-AC_MSG_CHECKING([whether compiler supports -std=c++14])
+# -std=c++20
+AC_MSG_CHECKING([whether compiler supports -std=c++20])
 old_CXXFLAGS="$CXXFLAGS"
-CXXFLAGS="-std=c++14"
+CXXFLAGS="-std=c++20"
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[ ]])],
 	AC_MSG_RESULT([yes])
-		std_cpp14="-std=c++14",
+		std_cpp14="-std=c++20",
 	AC_MSG_RESULT([no])
-		AC_MSG_ERROR([[Your compiler doesn't seem to support C++14, please upgrade (GCC >= 5)]])
+		AC_MSG_ERROR([[Your compiler doesn't seem to support C++20, please upgrade]])
 )
 CXXFLAGS="$old_CXXFLAGS $std_cpp14"
 

src/curses/window.h

@@ -26,7 +26,6 @@
 #include "config.h"
 
 #include "curses.h"
-#include "gcc.h"
 
 #include <boost/optional.hpp>
 #include <functional>

src/gcc.h

@@ -1,29 +0,0 @@
-/***************************************************************************
- *   Copyright (C) 2008-2021 by Andrzej Rybczak                            *
- *   andrzej@rybczak.net                                                   *
- *                                                                         *
- *   This program is free software; you can redistribute it and/or modify  *
- *   it under the terms of the GNU General Public License as published by  *
- *   the Free Software Foundation; either version 2 of the License, or     *
- *   (at your option) any later version.                                   *
- *                                                                         *
- *   This program is distributed in the hope that it will be useful,       *
- *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
- *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
- *   GNU General Public License for more details.                          *
- *                                                                         *
- *   You should have received a copy of the GNU General Public License     *
- *   along with this program; if not, write to the                         *
- *   Free Software Foundation, Inc.,                                       *
- *   51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.              *
- ***************************************************************************/
-
-#if defined(__GNUC__) && __GNUC__ >= 3
-# define GNUC_NORETURN __attribute__((noreturn))
-# define GNUC_UNUSED __attribute__((unused))
-# define GNUC_PRINTF(a, b) __attribute__((format(printf, a, b)))
-#else
-# define GNUC_NORETURN
-# define GNUC_UNUSED
-# define GNUC_PRINTF(a, b)
-#endif

src/interfaces.h

@@ -25,7 +25,6 @@
 #include <boost/tuple/tuple.hpp>
 #include <string>
 #include "enums.h"
-#include "gcc.h"
 #include "screens/screen.h"
 #include "song.h"
 

src/lyrics_fetcher.cpp

@@ -134,9 +134,11 @@ void LyricsFetcher::postProcess(std::string &data) const
 	boost::split(lines, data, boost::is_any_of("\n"));
 	for (auto &line : lines)
 		boost::trim(line);
-	std::unique(lines.begin(), lines.end(), [](std::string &a, std::string &b) {
-		return a.empty() && b.empty();
-	});
+	auto last = std::unique(
+		lines.begin(),
+		lines.end(),
+		[](std::string &a, std::string &b) { return a.empty() && b.empty(); });
+	lines.erase(last, lines.end());
 	data = boost::algorithm::join(lines, "\n");
 	boost::trim(data);
 }

src/mpdpp.h

@@ -353,8 +353,14 @@ private:
 };
 
 template <typename ObjectT>
-struct Iterator: std::iterator<std::input_iterator_tag, ObjectT>
+struct Iterator
 {
+	using iterator_category = std::input_iterator_tag;
+	using value_type = ObjectT;
+	using difference_type = std::ptrdiff_t;
+	using pointer = ObjectT *;
+	using reference = ObjectT &;
+
 	// shared state of the iterator
 	struct State
 	{

src/ncmpcpp.cpp

@@ -219,7 +219,10 @@ int main(int argc, char **argv)
 			try
 			{
 				auto k = Bindings.get(input);
-				std::any_of(k.first, k.second, std::bind(&Binding::execute, ph::_1));
+				[[maybe_unused]] bool executed = std::any_of(
+					k.first,
+					k.second,
+					std::bind(&Binding::execute, ph::_1));
 			}
 			catch (ConversionError &e)
 			{

src/regex_filter.h

@@ -93,7 +93,7 @@ inline Regex make(StringT &&s,
 template <typename CharT>
 inline bool search(const std::basic_string<CharT> &s,
                    const Regex &rx,
-                   GNUC_UNUSED bool ignore_diacritics)
+                   [[maybe_unused]] bool ignore_diacritics)
 {
 	try {
 #ifdef BOOST_REGEX_ICU

src/settings.cpp

@@ -472,10 +472,10 @@ bool Configuration::read(const std::vector<std::string> &config_paths, bool igno
 			      }
 			      return fetcher;
 		      });
-		      auto it = std::remove_if(
+		      auto last = std::remove_if(
 			      lyrics_fetchers.begin(), lyrics_fetchers.end(),
 			      [](const auto &f) { return f.get() == nullptr; });
-		      lyrics_fetchers.resize(it - lyrics_fetchers.begin());
+		      lyrics_fetchers.erase(last, lyrics_fetchers.end());
 		      if (lyrics_fetchers.empty())
 			      invalid_value(v);
 	      });

src/statusbar.h

@@ -24,7 +24,6 @@
 #include <boost/format.hpp>
 #include "curses/window.h"
 #include "settings.h"
-#include "gcc.h"
 #include "interfaces.h"
 
 namespace Progressbar {

src/utility/conversion.h

@@ -26,7 +26,6 @@
 #include <boost/type_traits/is_unsigned.hpp>
 
 #include "config.h"
-#include "gcc.h"
 
 struct ConversionError
 {
@@ -44,21 +43,21 @@ struct OutOfBounds : std::exception
 	const std::string &errorMessage() { return m_error_message; }
 	
 	template <typename Type>
-	GNUC_NORETURN static void raise(const Type &value, const Type &lbound, const Type &ubound)
+	[[noreturn]] static void raise(const Type &value, const Type &lbound, const Type &ubound)
 	{
 		throw OutOfBounds((boost::format(
 			"value is out of bounds ([%1%, %2%] expected, %3% given)") % lbound % ubound % value).str());
 	}
 	
 	template <typename Type>
-	GNUC_NORETURN static void raiseLower(const Type &value, const Type &lbound)
+	[[noreturn]] static void raiseLower(const Type &value, const Type &lbound)
 	{
 		throw OutOfBounds((boost::format(
 			"value is out of bounds ([%1%, ->) expected, %2% given)") % lbound % value).str());
 	}
 	
 	template <typename Type>
-	GNUC_NORETURN static void raiseUpper(const Type &value, const Type &ubound)
+	[[noreturn]] static void raiseUpper(const Type &value, const Type &ubound)
 	{
 		throw OutOfBounds((boost::format(
 			"value is out of bounds ((<-, %1%] expected, %2% given)") % ubound % value).str());

src/utility/string.h

@@ -25,7 +25,6 @@
 #include <locale>
 #include <string>
 #include <vector>
-#include "gcc.h"
 
 template <size_t N> size_t const_strlen(const char (&)[N]) {
 	return N-1;