* lisp/emacs-lisp/gv.el (gv-define-simple-setter): Don't evaluate `val'

twice when `fix-return' is set.

Fixes: debbugs:12813

2 files changed, 7 insertions, 2 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index b88baaa2f0a..187ff2d7e1d 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,8 @@
 2012-11-07  Stefan Monnier  <monnier@iro.umontreal.ca>
 
+        * emacs-lisp/gv.el (gv-define-simple-setter): Don't evaluate `val'
+        twice when `fix-return' is set (bug#12813).
+
         * emacs-lisp/cl.el (defsetf): Pass the third arg to
         gv-define-simple-setter (bug#12812).
 
diff --git a/lisp/emacs-lisp/gv.el b/lisp/emacs-lisp/gv.el
index 3dd021f9e74..a0c412a9504 100644
--- a/lisp/emacs-lisp/gv.el
+++ b/lisp/emacs-lisp/gv.el
@@ -213,9 +213,11 @@ If FIX-RETURN is non-nil, then SETTER is not assumed to return VAL and
 instead the assignment is turned into (prog1 VAL (SETTER ARGS... VAL))
 so as to preserve the semantics of `setf'."
   (declare (debug (sexp (&or symbolp lambda-expr) &optional sexp)))
-  (let ((set-call `(cons ',setter (append args (list val)))))
   `(gv-define-setter ,name (val &rest args)
-     ,(if fix-return `(list 'prog1 val ,set-call) set-call))))
+     ,(if fix-return
+          `(macroexp-let2 nil v val
+             (cons ',setter (append args (list v))))
+        `(cons ',setter (append args (list val))))))
 
 ;;; Typical operations on generalized variables.