Add TDE_CXX_COMPILE_STDCXX macro to check and enforce C++ standard.

The macro is a simplified form of AX_CXX_COMPILE_STDCXX from autoconf.
To verify the C++ standard supported by the compiler, only the value
of the __cplusplus constant defined by the compiler is checked,
instead of testing examples of using individual C++ features.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

1 files changed, 212 insertions, 0 deletions

diff --git a/acinclude.m4.in b/acinclude.m4.in
index d5c64c7..d5e9008 100644
--- a/acinclude.m4.in
+++ b/acinclude.m4.in
@@ -6451,3 +6451,215 @@ EOF
     AC_SUBST(LIBSQLITE3) 
   fi
 ])
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   TDE_CXX_COMPILE_STDCXX(VERSION, [ext|noext], [mandatory|optional])
+#
+# DESCRIPTION
+#
+#   Check for baseline language coverage in the compiler for the specified
+#   version of the C++ standard.  If necessary, add switches to CXX and
+#   CXXCPP to enable support.  VERSION may be '11' (for the C++11 standard)
+#   or '14' (for the C++14 standard).
+#
+#   The second argument, if specified, indicates whether you insist on an
+#   extended mode (e.g. -std=gnu++11) or a strict conformance mode (e.g.
+#   -std=c++11).  If neither is specified, you get whatever works, with
+#   preference for no added switch, and then for an extended mode.
+#
+#   The third argument, if specified 'mandatory' or if left unspecified,
+#   indicates that baseline support for the specified C++ standard is
+#   required and that the macro should error out if no mode with that
+#   support is found.  If specified 'optional', then configuration proceeds
+#   regardless, after defining HAVE_CXX${VERSION} if and only if a
+#   supporting mode is found.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Benjamin Kosnik <bkoz@redhat.com>
+#   Copyright (c) 2012 Zack Weinberg <zackw@panix.com>
+#   Copyright (c) 2013 Roy Stogner <roystgnr@ices.utexas.edu>
+#   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, 2018 Krzesimir Nowak <qdlacz@gmail.com>
+#   Copyright (c) 2019 Enji Cooper <yaneurabeya@gmail.com>
+#   Copyright (c) 2020 Jason Merrill <jason@redhat.com>
+#   Copyright (c) 2021 Slávek Banko <slavek.banko@axis.cz>
+#
+#   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.
+
+dnl  This macro is simplified version of the macro AX_CXX_COMPILE_STDCXX
+
+AC_DEFUN([TDE_CXX_COMPILE_STDCXX], [dnl
+  m4_if([$1], [11], [tde_cxx_compile_alternatives="11 0x"],
+        [$1], [14], [tde_cxx_compile_alternatives="14 1y"],
+        [$1], [17], [tde_cxx_compile_alternatives="17 1z"],
+        [m4_fatal([invalid first argument `$1' to TDE_CXX_COMPILE_STDCXX])])dnl
+  m4_if([$2], [], [],
+        [$2], [ext], [],
+        [$2], [noext], [],
+        [m4_fatal([invalid second argument `$2' to TDE_CXX_COMPILE_STDCXX])])dnl
+  m4_if([$3], [], [tde_cxx_compile_cxx$1_required=true],
+        [$3], [mandatory], [tde_cxx_compile_cxx$1_required=true],
+        [$3], [optional], [tde_cxx_compile_cxx$1_required=false],
+        [m4_fatal([invalid third argument `$3' to TDE_CXX_COMPILE_STDCXX])])
+  AC_LANG_PUSH([C++])dnl
+  ac_success=no
+
+  m4_if([$2], [], [dnl
+    AC_CACHE_CHECK(whether $CXX supports C++$1 features by default,
+                   tde_cv_cxx_compile_cxx$1,
+      [AC_COMPILE_IFELSE([AC_LANG_SOURCE([_TDE_CXX_COMPILE_STDCXX_testbody_$1])],
+        [tde_cv_cxx_compile_cxx$1=yes],
+        [tde_cv_cxx_compile_cxx$1=no])])
+    if test x$tde_cv_cxx_compile_cxx$1 = xyes; then
+      ac_success=yes
+    fi])
+
+  m4_if([$2], [noext], [], [dnl
+  if test x$ac_success = xno; then
+    for alternative in ${tde_cxx_compile_alternatives}; do
+      switch="-std=gnu++${alternative}"
+      cachevar=AS_TR_SH([tde_cv_cxx_compile_cxx$1_$switch])
+      AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+                     $cachevar,
+        [ac_save_CXX="$CXX"
+         CXX="$CXX $switch"
+         AC_COMPILE_IFELSE([AC_LANG_SOURCE([_TDE_CXX_COMPILE_STDCXX_testbody_$1])],
+          [eval $cachevar=yes],
+          [eval $cachevar=no])
+         CXX="$ac_save_CXX"])
+      if eval test x\$$cachevar = xyes; then
+        CXX="$CXX $switch"
+        if test -n "$CXXCPP" ; then
+          CXXCPP="$CXXCPP $switch"
+        fi
+        ac_success=yes
+        break
+      fi
+    done
+  fi])
+
+  m4_if([$2], [ext], [], [dnl
+  if test x$ac_success = xno; then
+    dnl HP's aCC needs +std=c++11 according to:
+    dnl http://h21007.www2.hp.com/portal/download/files/unprot/aCxx/PDF_Release_Notes/769149-001.pdf
+    dnl Cray's crayCC needs "-h std=c++11"
+    for alternative in ${tde_cxx_compile_alternatives}; do
+      for switch in -std=c++${alternative} +std=c++${alternative} "-h std=c++${alternative}"; do
+        cachevar=AS_TR_SH([tde_cv_cxx_compile_cxx$1_$switch])
+        AC_CACHE_CHECK(whether $CXX supports C++$1 features with $switch,
+                       $cachevar,
+          [ac_save_CXX="$CXX"
+           CXX="$CXX $switch"
+           AC_COMPILE_IFELSE([AC_LANG_SOURCE([_TDE_CXX_COMPILE_STDCXX_testbody_$1])],
+            [eval $cachevar=yes],
+            [eval $cachevar=no])
+           CXX="$ac_save_CXX"])
+        if eval test x\$$cachevar = xyes; then
+          CXX="$CXX $switch"
+          if test -n "$CXXCPP" ; then
+            CXXCPP="$CXXCPP $switch"
+          fi
+          ac_success=yes
+          break
+        fi
+      done
+      if test x$ac_success = xyes; then
+        break
+      fi
+    done
+  fi])
+  AC_LANG_POP([C++])
+  if test x$tde_cxx_compile_cxx$1_required = xtrue; then
+    if test x$ac_success = xno; then
+      AC_MSG_ERROR([*** A compiler with support for C++$1 language features is required.])
+    fi
+  fi
+  if test x$ac_success = xno; then
+    HAVE_CXX$1=0
+    AC_MSG_NOTICE([No compiler with C++$1 support was found])
+  else
+    HAVE_CXX$1=1
+    AC_DEFINE(HAVE_CXX$1,1,
+              [define if the compiler supports basic C++$1 syntax])
+  fi
+  AC_SUBST(HAVE_CXX$1)
+])
+
+
+dnl  Test body for checking C++11 support
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_11],
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_11
+)
+
+
+dnl  Test body for checking C++14 support
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_14],
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_11
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_14
+)
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_17],
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_11
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_14
+  _TDE_CXX_COMPILE_STDCXX_testbody_new_in_17
+)
+
+dnl  Tests for new features in C++11
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_new_in_11], [[
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201103L
+
+#error "This is not a C++11 compiler"
+
+#endif  // __cplusplus >= 201103L
+
+]])
+
+
+dnl  Tests for new features in C++14
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_new_in_14], [[
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201402L
+
+#error "This is not a C++14 compiler"
+
+#endif  // __cplusplus >= 201402L
+
+]])
+
+
+dnl  Tests for new features in C++17
+
+m4_define([_TDE_CXX_COMPILE_STDCXX_testbody_new_in_17], [[
+
+#ifndef __cplusplus
+
+#error "This is not a C++ compiler"
+
+#elif __cplusplus < 201703L
+
+#error "This is not a C++17 compiler"
+
+#endif  // __cplusplus >= 201703L
+
+]])