Enforce C++17 at the compiler level

configure.ac

@@ -25,7 +25,7 @@ AM_INIT_AUTOMAKE([1.11 -Wall -Wno-portability foreign no-dist-gzip dist-xz tar-p
 
 AC_PROG_CC
 AC_PROG_CXX
-AX_CXX_COMPILE_STDCXX_14
+AX_CXX_COMPILE_STDCXX_17
 
 AC_CANONICAL_HOST
 case ${host_os} in

license.txt

@@ -27,14 +27,15 @@ Copyright: 2008-2009 Thomas Porschberg <thomas@randspringer.de>
 License: FSFAP
 
 Files: m4/ax_cxx_compile_stdcxx.m4
-       m4/ax_cxx_compile_stdcxx_14.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 Krzesimir Nowak <qdlacz@gmail.com>
+           2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
+           2019 Enji Cooper <yaneurabeya@gmail.com>
 License: FSFAP
 
 Files: m4/ax_latex_class.m4 m4/ax_tex_test.m4

m4/ax_cxx_compile_stdcxx.m4

@@ -33,19 +33,19 @@
 #   Copyright (c) 2014, 2015 Google Inc.; contributed by Alexey Sokolov <sokolov@google.com>
 #   Copyright (c) 2015 Paul Norman <penorman@mac.com>
 #   Copyright (c) 2015 Moritz Klammler <moritz@klammler.eu>
-#   Copyright (c) 2016 Krzesimir Nowak <qdlacz@gmail.com>
+#   Copyright (c) 2016, 2018 Krzesimir Nowak <qdlacz@gmail.com>
+#   Copyright (c) 2019 Enji Cooper <yaneurabeya@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 7
+#serial 11
 
 dnl  This macro is based on the code from the AX_CXX_COMPILE_STDCXX_11 macro
 dnl  (serial version number 13).
 
-AX_REQUIRE_DEFINED([AC_MSG_WARN])
 AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
   m4_if([$1], [11], [ax_cxx_compile_alternatives="11 0x"],
         [$1], [14], [ax_cxx_compile_alternatives="14 1y"],
@@ -61,14 +61,6 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
         [m4_fatal([invalid third argument `$3' to AX_CXX_COMPILE_STDCXX])])
   AC_LANG_PUSH([C++])dnl
   ac_success=no
-  AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
-  ax_cv_cxx_compile_cxx$1,
-  [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_AX_CXX_COMPILE_STDCXX_testbody_$1])],
-    [ax_cv_cxx_compile_cxx$1=yes],
-    [ax_cv_cxx_compile_cxx$1=no])])
-  if test x$ax_cv_cxx_compile_cxx$1 = xyes; then
-    ac_success=yes
-  fi
 
   m4_if([$2], [noext], [], [dnl
   if test x$ac_success = xno; then
@@ -139,7 +131,6 @@ AC_DEFUN([AX_CXX_COMPILE_STDCXX], [dnl
               [define if the compiler supports basic C++$1 syntax])
   fi
   AC_SUBST(HAVE_CXX$1)
-  m4_if([$1], [17], [AC_MSG_WARN([C++17 is not yet standardized, so the checks may change in incompatible ways anytime])])
 ])
 
 
@@ -199,11 +190,13 @@ namespace cxx11
 
     struct Base
     {
+      virtual ~Base() {}
       virtual void f() {}
     };
 
     struct Derived : public Base
     {
+      virtual ~Derived() override {}
       virtual void f() override {}
     };
 
@@ -587,20 +580,12 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
 
 #error "This is not a C++ compiler"
 
-#elif __cplusplus <= 201402L
+#elif __cplusplus < 201703L
 
 #error "This is not a C++17 compiler"
 
 #else
 
-#if defined(__clang__)
-  #define REALLY_CLANG
-#else
-  #if defined(__GNUC__)
-    #define REALLY_GCC
-  #endif
-#endif
-
 #include <initializer_list>
 #include <utility>
 #include <type_traits>
@@ -608,16 +593,12 @@ m4_define([_AX_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
 namespace cxx17
 {
 
-#if !defined(REALLY_CLANG)
   namespace test_constexpr_lambdas
   {
 
-    // TODO: test it with clang++ from git
-
     constexpr int foo = [](){return 42;}();
 
   }
-#endif // !defined(REALLY_CLANG)
 
   namespace test::nested_namespace::definitions
   {
@@ -852,12 +833,9 @@ namespace cxx17
 
   }
 
-#if !defined(REALLY_CLANG)
   namespace test_template_argument_deduction_for_class_templates
   {
 
-    // TODO: test it with clang++ from git
-
     template <typename T1, typename T2>
     struct pair
     {
@@ -876,7 +854,6 @@ namespace cxx17
     }
 
   }
-#endif // !defined(REALLY_CLANG)
 
   namespace test_non_type_auto_template_parameters
   {
@@ -890,12 +867,9 @@ namespace cxx17
 
   }
 
-#if !defined(REALLY_CLANG)
   namespace test_structured_bindings
   {
 
-    // TODO: test it with clang++ from git
-
     int arr[2] = { 1, 2 };
     std::pair<int, int> pr = { 1, 2 };
 
@@ -927,14 +901,10 @@ namespace cxx17
     const auto [ x3, y3 ] = f3();
 
   }
-#endif // !defined(REALLY_CLANG)
 
-#if !defined(REALLY_CLANG)
   namespace test_exception_spec_type_system
   {
 
-    // TODO: test it with clang++ from git
-
     struct Good {};
     struct Bad {};
 
@@ -952,7 +922,6 @@ namespace cxx17
     static_assert (std::is_same_v<Good, decltype(f(g1, g2))>);
 
   }
-#endif // !defined(REALLY_CLANG)
 
   namespace test_inline_variables
   {
@@ -977,6 +946,6 @@ namespace cxx17
 
 }  // namespace cxx17
 
-#endif  // __cplusplus <= 201402L
+#endif  // __cplusplus < 201703L
 
 ]])

m4/ax_cxx_compile_stdcxx_14.m4 → m4/ax_cxx_compile_stdcxx_17.m4

 # =============================================================================
-#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_14.html
+#  https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_17.html
 # =============================================================================
 #
 # SYNOPSIS
 #
-#   AX_CXX_COMPILE_STDCXX_14([ext|noext], [mandatory|optional])
+#   AX_CXX_COMPILE_STDCXX_17([ext|noext], [mandatory|optional])
 #
 # DESCRIPTION
 #
-#   Check for baseline language coverage in the compiler for the C++14
+#   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++14.  The two optional arguments are
+#   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
@@ -22,13 +22,14 @@
 # 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 5
+#serial 2
 
 AX_REQUIRE_DEFINED([AX_CXX_COMPILE_STDCXX])
-AC_DEFUN([AX_CXX_COMPILE_STDCXX_14], [AX_CXX_COMPILE_STDCXX([14], [$1], [$2])])
+AC_DEFUN([AX_CXX_COMPILE_STDCXX_17], [AX_CXX_COMPILE_STDCXX([17], [$1], [$2])])