Autotools: use C++17 mode when available

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index a3bb1148953f26d5405bdf647f9cf238aac858f3..d07e1bcfccde15bd2ba46e74207e3ec98efa9230 100644 (file)
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -270,8 +270,8 @@ AC_REQUIRE([AC_PROG_CXXCPP])
 
 ### We might want to force the C++ standard.
 AC_ARG_ENABLE(cxx-mode,
-  AS_HELP_STRING([--enable-cxx-mode],[choose C++ standard (default: 14, then 11)]),,
-  [enable_cxx_mode={14,11}]
+  AS_HELP_STRING([--enable-cxx-mode],[choose C++ standard (default: 17, 14, then 11)]),,
+  [enable_cxx_mode={17,14,11}]
 )
 
 AC_LANG_PUSH(C++)