byte-compile-setq-default fix for bug#12195

* lisp/emacs-lisp/bytecomp.el (byte-compile-setq-default):
Optimize away setq-default with no args, as is done for setq.

2 files changed, 21 insertions, 14 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 606be46b118..b58580f6429 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-08-14  Glenn Morris  <rgm@gnu.org>
+
+        * emacs-lisp/bytecomp.el (byte-compile-setq-default):
+        Optimize away setq-default with no args, as for setq.  (Bug#12195)
+
 2012-08-14  Chong Yidong  <cyd@gnu.org>
 
         * minibuffer.el (read-file-name): Doc fix (Bug#10881).
diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index abfd73cb438..10bc37c6dcd 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -3578,20 +3578,22 @@ discarding."
 
 (defun byte-compile-setq-default (form)
   (setq form (cdr form))
-  (if (> (length form) 2)
-      (let ((setters ()))
-        (while (consp form)
-          (push `(setq-default ,(pop form) ,(pop form)) setters))
-        (byte-compile-form (cons 'progn (nreverse setters))))
-    (let ((var (car form)))
-      (and (or (not (symbolp var))
-               (macroexp--const-symbol-p var t))
-           (byte-compile-warning-enabled-p 'constants)
-           (byte-compile-warn
-            "variable assignment to %s `%s'"
-            (if (symbolp var) "constant" "nonvariable")
-            (prin1-to-string var)))
-      (byte-compile-normal-call `(set-default ',var ,@(cdr form))))))
+  (if (null form)                       ; (setq-default), with no arguments
+      (byte-compile-form nil byte-compile--for-effect)
+    (if (> (length form) 2)
+        (let ((setters ()))
+          (while (consp form)
+            (push `(setq-default ,(pop form) ,(pop form)) setters))
+          (byte-compile-form (cons 'progn (nreverse setters))))
+      (let ((var (car form)))
+        (and (or (not (symbolp var))
+                 (macroexp--const-symbol-p var t))
+             (byte-compile-warning-enabled-p 'constants)
+             (byte-compile-warn
+              "variable assignment to %s `%s'"
+              (if (symbolp var) "constant" "nonvariable")
+              (prin1-to-string var)))
+        (byte-compile-normal-call `(set-default ',var ,@(cdr form)))))))
 
 (byte-defop-compiler-1 set-default)
 (defun byte-compile-set-default (form)