configure check for stdc++fs

configure

@@ -5817,6 +5817,59 @@ else
 fi
 
 
+ac_fn_cxx_check_header_mongrel "$LINENO" "filesystem" "ac_cv_header_filesystem" "$ac_includes_default"
+if test "x$ac_cv_header_filesystem" = xyes; then :
+
+else
+  as_fn_error $? "The file <filesystem> is missing, perhaps you should install a more recent libstdc++ implementation." "$LINENO" 5
+fi
+
+
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <filesystem>
+int
+main ()
+{
+(void)std::filesystem::current_path();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+
+else
+
+		LIBS="$LIBS -lstdc++fs"
+
+		cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <filesystem>
+int
+main ()
+{
+(void)std::filesystem::current_path();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+
+else
+
+				as_fn_error $? "Could not link filesystem" "$LINENO" 5
+
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
+
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+
 
 
 # Check whether --with-boost was given.

configure.ac

@@ -43,6 +43,27 @@ AX_CHECK_LIBRARY([LIBCIFPP], [cif++/Config.hpp], [cif++],
 	[],
 	[AC_MSG_ERROR([libcif++ not found - cannot continue])])
 
+AC_CHECK_HEADER([filesystem], [], [AC_MSG_ERROR([The file <filesystem> is missing, perhaps you should install a more recent libstdc++ implementation.])])
+
+dnl check if we need stdc++fs as library
+AC_TRY_LINK(
+	[#include <filesystem>],
+	[(void)std::filesystem::current_path();],
+	[],
+	[
+		LIBS="$LIBS -lstdc++fs"
+
+		AC_TRY_LINK(
+			[#include <filesystem>],
+			[(void)std::filesystem::current_path();],
+			[],
+			[
+				AC_MSG_ERROR([Could not link filesystem])
+			]
+		)
+	]
+)
+
 AX_BOOST_BASE([1.65.1], [], [AC_MSG_ERROR([Could not find a recent version of boost])])
 AX_BOOST_IOSTREAMS
 AX_BOOST_THREAD