(Vhistory_length, Qhistory_length): New variables.

(syms_of_minibuf): Register and initialise these.
(read_minibuf): Truncate history list if needed.

diff --git a/src/minibuf.c b/src/minibuf.c
index 0d107f97b1bdfb4f743cc6e7dd12aa21827476df..35f562fa0e5c45dad0d84c0c04c62d64d54505ff 100644 (file)
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -46,9 +46,12 @@ Lisp_Object minibuf_save_list;
 /* Depth in minibuffer invocations.  */
 int minibuf_level;
 
-/* Nonzero means display completion help for invalid input */
+/* Nonzero means display completion help for invalid input.  */
 int auto_help;
 
+/* The maximum length of a minibuffer history.  */
+Lisp_Object Qhistory_length, Vhistory_length;
+
 /* Fread_minibuffer leaves the input here as a string. */
 Lisp_Object last_minibuf_string;
 
@@ -356,8 +359,27 @@ read_minibuf (map, initial, prompt, backup_n, expflag, histvar, histpos)
       if (NILP (histval)
          || (CONSP (histval)
              && NILP (Fequal (last_minibuf_string, Fcar (histval)))))
-       Fset (Vminibuffer_history_variable,
-             Fcons (last_minibuf_string, histval));
+       {
+         Lisp_Object length;
+
+         histval = Fcons (last_minibuf_string, histval);
+         Fset (Vminibuffer_history_variable, histval);
+
+         /* Truncate if requested.  */
+         length = Fget (Vminibuffer_history_variable, Qhistory_length);
+         if (NILP (length)) length = Vhistory_length;
+         if (INTEGERP (length)) {
+           if (XINT (length) <= 0)
+             Fset (Vminibuffer_history_variable, Qnil);
+           else
+             {
+               Lisp_Object temp;
+
+               temp = Fnthcdr (Fsub1 (length), histval);
+               if (CONSP (temp)) Fsetcdr (temp, Qnil);
+             }
+         }
+       }
     }
 
   /* If Lisp form desired instead of string, parse it. */
@@ -1794,6 +1816,9 @@ syms_of_minibuf ()
   Qminibuffer_exit_hook = intern ("minibuffer-exit-hook");
   staticpro (&Qminibuffer_exit_hook);
 
+  Qhistory_length = intern ("history-length");
+  staticpro (&Qhistory_length);
+
   DEFVAR_LISP ("minibuffer-setup-hook", &Vminibuffer_setup_hook, 
     "Normal hook run just after entry to minibuffer.");
   Vminibuffer_setup_hook = Qnil;
@@ -1802,6 +1827,13 @@ syms_of_minibuf ()
     "Normal hook run just after exit from minibuffer.");
   Vminibuffer_exit_hook = Qnil;
 
+  DEFVAR_LISP ("history-length", &Vhistory_length,
+    "*Maximum length for history lists before truncation takes place.\n\
+A number means that length; t means infinite.  Truncation takes place\n\
+just after a new element is inserted.  Setting the history-length\n\
+property of a history variable overrides this default.");
+  XSETFASTINT (Vhistory_length, 30);
+
   DEFVAR_BOOL ("completion-auto-help", &auto_help,
     "*Non-nil means automatically provide help for invalid completion input.");
   auto_help = 1;