Index: readline.scm
===================================================================
--- readline.scm	(revision 705)
+++ readline.scm	(working copy)
@@ -55,6 +55,8 @@
   gnu-readline-write-history
   gnu-readline-truncate-history
   gnu-history-install-file-manager
+
+  *completion-entry-function*
  )
 
  (foreign-declare #<<EOF
@@ -65,14 +67,48 @@
 
 static char *readline_buf = NULL;
 
+// Can't use const char* text.  See its definition for an explanation.
+
+char *C_default_completion ( char *text, int pos );
+
+char *C_readline_completion ( const char *text, int pos )
+{
+  char *result = C_default_completion(text, pos);
+  return result[0] == 0 ? NULL : strdup(result);
+}
 EOF
 ))
 
 ; Initialise the history library.
 ((foreign-lambda void "using_history"))
 
+(define *completion-entry-function* (lambda args '()))
+
+(define *completions* #f)
+
+; We should return #f when we run out of completions instead of "".  However,
+; returning #f causes segmentation faults (perhaps because of a bug in
+; Chicken's handling of #f when the c-string foreign type is used?).
+
+; Also, we should use (const c-string) instead of c-string but it triggers
+; some weird bug where "text" gets passed as a c-pointer rather than as a
+; string.
+
+(define-external (C_default_completion (c-string text) (int pos)) c-string
+  (when (zero? pos)
+    (set! *completions* (list->vector (*completion-entry-function* text))))
+  (if (< pos (vector-length *completions*))
+    (vector-ref *completions* pos)
+    ""))
+
+((foreign-lambda* void () #<<EOF
+  rl_completion_entry_function = C_readline_completion;
+  rl_basic_word_break_characters = " \t\n\"\\'`;|{(";
+EOF
+))
+
 (define gnu-readline
-  (foreign-lambda* c-string ((c-string prompt))
+  (foreign-safe-lambda* c-string ((c-string prompt))
 		   "if (readline_buf != NULL) {"
 		   "  free(readline_buf);"
 		   "  readline_buf = NULL;"