Bump to C++20 standard (with GNU extensions)

In practice, for the time being, we limit ourselves to C++20 features available
in GCC 10.

README.md

@@ -67,7 +67,7 @@ a 32-bit Octave.
 A number of tools and libraries are needed in order to recompile everything. You don't necessarily need to install everything, depending on what you want to compile.
 
 - A POSIX compliant shell and an implementation of Make (mandatory)
-- The [GNU Compiler Collection](http://gcc.gnu.org/), version 9 or later, with
+- The [GNU Compiler Collection](http://gcc.gnu.org/), version 10 or later, with
   gcc, g++ and gfortran (mandatory)
 - [MATLAB](https://mathworks.com) (if you want to compile the MEX for MATLAB)
 - [GNU Octave](http://www.octave.org) with

configure.ac

 dnl Process this file with autoconf to produce a configure script.
 
-dnl Copyright © 2009-2021 Dynare Team
+dnl Copyright © 2009-2022 Dynare Team
 dnl
 dnl This file is part of Dynare.
 dnl
@@ -26,7 +26,6 @@ AC_CONFIG_SUBDIRS([preprocessor])
 
 AC_PROG_CC
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_17
 
 AC_CANONICAL_HOST
 case ${host_os} in
@@ -50,7 +49,7 @@ esac
 # Use C++ for testing headers
 AC_LANG([C++])
 
-AM_CXXFLAGS="-Wall -Wno-parentheses -Wold-style-cast"
+AM_CXXFLAGS="-std=gnu++20 -Wall -Wno-parentheses -Wold-style-cast"
 AC_SUBST([AM_CXXFLAGS])
 
 # If default 'ar' is not available, try to find one with a host prefix (see ticket #145)

license.txt

@@ -292,19 +292,6 @@ Files: m4/ax_compare_version.m4
 Copyright: 2008 Tim Toolan <toolan@ele.uri.edu>
 License: FSFAP
 
-Files: m4/ax_cxx_compile_stdcxx.m4
-       m4/ax_cxx_compile_stdcxx_17.m4
-Copyright: 2008 Benjamin Kosnik <bkoz@redhat.com>
-           2012 Zack Weinberg <zackw@panix.com>
-           2013 Roy Stogner <roystgnr@ices.utexas.edu>
-           2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
-           2015 Paul Norman <penorman@mac.com>
-           2015 Moritz Klammler <moritz@klammler.eu>
-           2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
-           2019 Enji Cooper <yaneurabeya@gmail.com>
-           2020 Jason Merrill <jason@redhat.com>
-License: FSFAP
-
 Files: m4/ax_latex_class.m4 m4/ax_latex_test.m4
 Copyright: 2008 Boretti Mathieu <boretti@eig.unige.ch>
            2009 Dynare Team
@@ -341,19 +328,6 @@ Copyright: 2008-2009 Thomas Porschberg <thomas@randspringer.de>
            2009 Peter Adolphs
 License: FSFAP
 
-Files: preprocessor/m4/ax_cxx_compile_stdcxx.m4
-       preprocessor/m4/ax_cxx_compile_stdcxx_17.m4
-Copyright: 2008 Benjamin Kosnik <bkoz@redhat.com>
-           2012 Zack Weinberg <zackw@panix.com>
-           2013 Roy Stogner <roystgnr@ices.utexas.edu>
-           2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
-           2015 Paul Norman <penorman@mac.com>
-           2015 Moritz Klammler <moritz@klammler.eu>
-           2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
-           2019 Enji Cooper <yaneurabeya@gmail.com>
-           2020 Jason Merrill <jason@redhat.com>
-License: FSFAP
-
 Files: preprocessor/m4/ax_latex_class.m4
        preprocessor/m4/ax_latex_test.m4
 Copyright: 2008 Boretti Mathieu <boretti@eig.unige.ch>

m4/ax_cxx_compile_stdcxx_17.m4

-# =============================================================================
-#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_17.html
-# =============================================================================
-#
-# SYNOPSIS
-#
-#   AX_CXX_COMPILE_STDCXX_17([ext|noext], [mandatory|optional])
-#
-# DESCRIPTION
-#
-#   Check for baseline language coverage in the compiler for the C++17
-#   standard; if necessary, add switches to CXX and CXXCPP to enable
-#   support.
-#
-#   This macro is a convenience alias for calling the AX_CXX_COMPILE_STDCXX
-#   macro with the version set to C++17.  The two optional arguments are
-#   forwarded literally as the second and third argument respectively.
-#   Please see the documentation for the AX_CXX_COMPILE_STDCXX macro for
-#   more information.  If you want to use this macro, you also need to
-#   download the ax_cxx_compile_stdcxx.m4 file.
-#
-# LICENSE
-#
-#   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
-#   Copyright (c) 2016 Krzesimir Nowak <qdlacz@gmail.com>
-#
-#   Copying and distribution of this file, with or without modification, are
-#   permitted in any medium without royalty provided the copyright notice
-#   and this notice are preserved. This file is offered as-is, without any
-#   warranty.
-
-#serial 2
-
-AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
-AC_DEFUN([AX_CXX_COMPILE_STDCXX_17], [AX_CXX_COMPILE_STDCXX([17], [$1], [$2])])

mex/build/matlab/configure.ac

@@ -48,7 +48,6 @@ esac
 AC_PROG_FC
 AC_PROG_CC
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_17
 AC_PROG_RANLIB
 AX_PROG_LN_S
 AC_PROG_MKDIR_P

mex/build/matlab/mex.am

@@ -9,7 +9,7 @@ DEFS += -DMEXEXT=\"$(MEXEXT)\"
 
 AM_CFLAGS = $(MATLAB_CFLAGS) -Wall -Wno-parentheses
 AM_FCFLAGS = $(MATLAB_FCFLAGS) -Wall -Wimplicit-interface
-AM_CXXFLAGS = $(MATLAB_CXXFLAGS) -Wall -Wno-parentheses -Wold-style-cast
+AM_CXXFLAGS = -std=gnu++20 $(MATLAB_CXXFLAGS) -Wall -Wno-parentheses -Wold-style-cast
 AM_LDFLAGS = $(MATLAB_LDFLAGS)
 LIBS += $(MATLAB_LIBS)
 

mex/build/octave/configure.ac

@@ -46,7 +46,6 @@ AX_COMPARE_VERSION([$OCTAVE_VERSION], [lt], [6.2.0], [AC_MSG_ERROR([Your Octave
 AC_PROG_FC
 AC_PROG_CC
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_17
 AC_PROG_RANLIB
 AX_PROG_LN_S
 AC_PROG_MKDIR_P

mex/build/octave/mex.am

@@ -7,7 +7,7 @@ DEFS += -DMEXEXT=\".mex\"
 
 AM_CFLAGS = $(shell $(MKOCTFILE) -p CPICFLAG) -Wall -Wno-parentheses
 AM_FCFLAGS = $(shell $(MKOCTFILE) -p FPICFLAG) -Wall -Wimplicit-interface
-AM_CXXFLAGS = $(shell $(MKOCTFILE) -p CXXPICFLAG) -Wall -Wno-parentheses -Wold-style-cast
+AM_CXXFLAGS = -std=gnu++20 $(shell $(MKOCTFILE) -p CXXPICFLAG) -Wall -Wno-parentheses -Wold-style-cast
 AM_LDFLAGS = $(shell $(MKOCTFILE) -p DL_LDFLAGS)
 
 # See the comments in configure.ac

preprocessor @ 46a85644

-Subproject commit 3a820fffa2f7291be5732c33bde552526eab1602
+Subproject commit 46a85644d8d1cd04a1e97b8121c99d94003b01f0