1 files changed, 12 insertions, 1 deletions
diff --git a/ext/readline/extconf.rb b/ext/readline/extconf.rb
index 431ed213bb..b883de3e01 100644
--- a/ext/readline/extconf.rb
+++ b/ext/readline/extconf.rb
@@ -10,7 +10,18 @@ if have_header("readline/readline.h") and
     have_header("readline/history.h") and
     have_library("readline", "readline")
   if have_func("rl_filename_completion_function")
-    $CFLAGS += "-DREADLINE_42_OR_LATER"
+    $CFLAGS += " -DREADLINE_42_OR_LATER"
+  end
+  if have_func("rl_cleanup_after_signal")
+    $CFLAGS += " -DREADLINE_40_OR_LATER"
+  end
+  if try_link(<<EOF, $libs)
+#include <stdio.h>
+#include <readline/readline.h>
+main() {rl_completion_append_character = 1;}
+EOF
+    # this feature is implemented in readline-2.1 or later. 
+    $CFLAGS += " -DREADLINE_21_OR_LATER"
   end
   create_makefile("readline")
 end