From b1be06125ea355e15555d79f0a63022f9bb7704e Mon Sep 17 00:00:00 2001
From: Gabriel Dos Reis <GabrielDosReis@users.noreply.github.com>
Date: Fri, 12 Aug 2022 17:26:03 -0700
Subject: Refactor Autconf macro for requiring C++ version. Require C++ 20.

---
 config/open-axiom.m4 | 12 ++++++------
 configure            |  4 ++--
 configure.ac         |  2 +-
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/config/open-axiom.m4 b/config/open-axiom.m4
index fce469bd..34fcaa6d 100644
--- a/config/open-axiom.m4
+++ b/config/open-axiom.m4
@@ -257,17 +257,17 @@ case $host in
 esac
 ])
 
-dnl -----------------------------
-dnl -- OPENAXIOM_REQUIRE_CXX17 --
-dnl -----------------------------
-AC_DEFUN([OPENAXIOM_REQUIRE_CXX17],[
+dnl ---------------------------
+dnl -- OPENAXIOM_REQUIRE_CXX --
+dnl ---------------------------
+AC_DEFUN([OPENAXIOM_REQUIRE_CXX],[
 oa_saved_cxxflags=$CXXFLAGS
-CXXFLAGS="-std=c++17"
+CXXFLAGS="-std=c++$1"
 AC_MSG_CHECKING([whether $CXX supports $CXXFLAGS])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
   [AC_MSG_RESULT([yes])]
   [CXXFLAGS="$CXXFLAGS $oa_saved_cxxflags"],
-  [AC_MSG_ERROR([OpenAxiom requires a C++17 compiler])])
+  [AC_MSG_ERROR([OpenAxiom requires a C++$1 compiler])])
 ])
 
 dnl -------------------------------
diff --git a/configure b/configure
index b7240475..b2b8aa75 100755
--- a/configure
+++ b/configure
@@ -6374,7 +6374,7 @@ fi
 
 
 oa_saved_cxxflags=$CXXFLAGS
-CXXFLAGS="-std=c++17"
+CXXFLAGS="-std=c++20"
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether $CXX supports $CXXFLAGS" >&5
 printf %s "checking whether $CXX supports $CXXFLAGS... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -6394,7 +6394,7 @@ then :
 printf "%s\n" "yes" >&6; }
   CXXFLAGS="$CXXFLAGS $oa_saved_cxxflags"
 else $as_nop
-  as_fn_error $? "OpenAxiom requires a C++17 compiler" "$LINENO" 5
+  as_fn_error $? "OpenAxiom requires a C++20 compiler" "$LINENO" 5
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
 
diff --git a/configure.ac b/configure.ac
index 9ffdd62b..8d324d9f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -90,7 +90,7 @@ AC_LANG([C++])
 
 OPENAXIOM_HOST_COMPILERS
 AM_CONDITIONAL([OA_USE_LLVM], [test -n $oa_use_llvm])
-OPENAXIOM_REQUIRE_CXX17
+OPENAXIOM_REQUIRE_CXX([20])
 OPENAXIOM_EXTRA_CXX_OPTIONS
 AM_CONDITIONAL([OA_BUILD_GCL], [test x$oa_include_gcl = xyes])
 AM_CONDITIONAL([OA_ECL_RT], [test x$oa_lisp_flavor = xecl])
-- 
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