+# 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])
+])
+