m4/ansi-c++.m4

# ansi-c++.m4
# serial 13
dnl Copyright (C) 2002-2003, 2005, 2010-2026 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl This file is offered as-is, without any warranty.

dnl From Bruno Haible.

# Sets CXX_CHOICE to 'yes' or 'no', depending on the preferred use of C++.
# The default is 'yes'. If the configure.ac contains a definition of the
# macro gl_CXX_CHOICE_DEFAULT_NO, then the default is 'no'. In both cases,
# the user can change the value by passing the option --disable-cxx or
# --enable-cxx, respectively.

AC_DEFUN([gl_CXX_CHOICE],
[
  AC_MSG_CHECKING([whether to use C++])
  dnl Plus signs are supported in AC_ARG_ENABLE starting with autoconf-2.66.
  m4_version_prereq([2.66],
    [m4_ifdef([gl_CXX_CHOICE_DEFAULT_NO],
       [AC_ARG_ENABLE([c++],
          [  --enable-c++            also build C++ sources],
          [CXX_CHOICE="$enableval"],
          [CXX_CHOICE=no])],
       [AC_ARG_ENABLE([c++],
          [  --disable-c++           do not build C++ sources],
          [CXX_CHOICE="$enableval"],
          [CXX_CHOICE=yes])])],
    [m4_ifdef([gl_CXX_CHOICE_DEFAULT_NO],
       [AC_ARG_ENABLE([cxx],
          [  --enable-cxx            also build C++ sources],
          [CXX_CHOICE="$enableval"],
          [CXX_CHOICE=no])],
       [AC_ARG_ENABLE([cxx],
          [  --disable-cxx           do not build C++ sources],
          [CXX_CHOICE="$enableval"],
          [CXX_CHOICE=yes])])])
  AC_MSG_RESULT([$CXX_CHOICE])
  AC_SUBST([CXX_CHOICE])
])

# gl_PROG_ANSI_CXX([ANSICXX_VARIABLE], [ANSICXX_CONDITIONAL])
# Sets ANSICXX_VARIABLE to the name of a sufficiently ANSI C++ compliant
# compiler, or to "no" if none is found.
# Defines the Automake condition ANSICXX_CONDITIONAL to true if such a compiler
# was found, or to false if not.

AC_DEFUN([gl_PROG_ANSI_CXX],
[
  AC_REQUIRE([gl_CXX_CHOICE])
  m4_if([$1], [CXX], [],
    [gl_saved_CXX="$CXX"])
  if test "$CXX_CHOICE" = no; then
    CXX=no
  fi
  if test -z "$CXX"; then
    if test -n "$CCC"; then
      CXX="$CCC"
    else
      AC_CHECK_TOOLS([CXX],
                     [g++ c++ gpp aCC CC cxx cc++ cl FCC KCC RCC xlC_r xlC],
                     [:])
    fi
  fi
  if test "$CXX" != no; then
    dnl Use a modified version of AC_PROG_CXX_WORKS that does not exit
    dnl upon failure.
    AC_MSG_CHECKING([whether the C++ compiler ($CXX $CXXFLAGS $LDFLAGS) works])
    AC_LANG_PUSH([C++])
    AC_ARG_VAR([CXX], [C++ compiler command])
    AC_ARG_VAR([CXXFLAGS], [C++ compiler flags])
    echo 'int main () { return 0; }' > conftest.$ac_ext
    if AC_TRY_EVAL([ac_link]) && test -s conftest$ac_exeext; then
      gl_cv_prog_ansicxx_works=yes
      if (./conftest; exit) 2>/dev/null; then
        gl_cv_prog_ansicxx_cross=no
      else
        gl_cv_prog_ansicxx_cross=yes
      fi
    else
      gl_cv_prog_ansicxx_works=no
    fi
    rm -fr conftest*
    AC_LANG_POP([C++])
    AC_MSG_RESULT([$gl_cv_prog_ansicxx_works])
    if test $gl_cv_prog_ansicxx_works = no; then
      CXX=no
    else
      dnl Test for namespaces.
      dnl We don't bother supporting pre-ANSI-C++ compilers.
      AC_MSG_CHECKING([whether the C++ compiler supports namespaces])
      AC_LANG_PUSH([C++])
      cat <<EOF > conftest.$ac_ext
#include <iostream>
namespace test { using namespace std; }
std::ostream* ptr;
int main () { return 0; }
EOF
      if AC_TRY_EVAL([ac_link]) && test -s conftest$ac_exeext; then
        gl_cv_prog_ansicxx_namespaces=yes
      else
        gl_cv_prog_ansicxx_namespaces=no
      fi
      rm -fr conftest*
      AC_LANG_POP([C++])
      AC_MSG_RESULT([$gl_cv_prog_ansicxx_namespaces])
      if test $gl_cv_prog_ansicxx_namespaces = no; then
        CXX=no
      fi
    fi
  fi
  m4_if([$1], [CXX], [],
    [$1="$CXX"
     CXX="$gl_saved_CXX"])
  AC_SUBST([$1])

  AM_CONDITIONAL([$2], [test "$$1" != no])

  if test "$$1" != no; then
    dnl This macro invocation resolves an automake error:
    dnl /usr/local/share/automake-1.11/am/depend2.am: am__fastdepCXX does not appear in AM_CONDITIONAL
    dnl /usr/local/share/automake-1.11/am/depend2.am:   The usual way to define 'am__fastdepCXX' is to add 'AC_PROG_CXX'
    dnl /usr/local/share/automake-1.11/am/depend2.am:   to 'configure.ac' and run 'aclocal' and 'autoconf' again.
    _AM_DEPENDENCIES([CXX])
    dnl Determine a good default for the CXXFLAGS variable.
    AC_LANG_PUSH([C++])
    _AC_LANG_COMPILER_GNU
    if test $ac_compiler_gnu = yes; then
      GXX=yes
    else
      GXX=
    fi
    _AC_PROG_CXX_G
    AC_LANG_POP([C++])
  else
    AM_CONDITIONAL([am__fastdepCXX], [false])
  fi
])

# gl_ANSI_CXX
# Sets CXX to the name of a sufficiently ANSI C++ compliant compiler, or to
# "no" if none is found.
# Defines the Automake condition ANSICXX to true if such a compiler was found,
# or to false if not.
AC_DEFUN([gl_ANSI_CXX],
[
  gl_PROG_ANSI_CXX([CXX], [ANSICXX])
  dnl This line is needed in order to avoid trouble with Autoconf.  It makes
  dnl sure that Autoconf does not insert expansions of AC_PROG_CXX at random
  dnl places.  See <https://savannah.gnu.org/support/?110294>.
  m4_provide([AC_PROG_CXX])
])