GNU bug report logs - #25965
26.0.50; iter-lambda may evaluate certain forms twice

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Message #16 received at control <at> debbugs.gnu.org (full text, mbox):

From: Gemini Lasswell <gazally <at> runbox.com>
To: Daniel Colascione <dancol <at> dancol.org>
Cc: 25965 <at> debbugs.gnu.org, Stefan Monnier <monnier <at> IRO.UMontreal.CA>,
 Andreas Politz <politza <at> hochschule-trier.de>
Subject: Re: bug#25965: 26.0.50; iter-lambda may evaluate certain forms twice
Date: Thu, 21 Sep 2017 14:36:34 -0700

[Message part 1 (text/plain, inline)]

tags 25965 patch
quit

Daniel Colascione <dancol <at> dancol.org> writes:

> I think it's safe to remove it. Let's make
> sure to add a test too.

Here's a patch which removes the second ,form and adds a test:

[0001-Fix-dynamic-binding-wrapper-in-iter-lambda-bug-25965.patch (text/plain, inline)]

From 46720f235ff11f64a35b91e74110fd3a8e01be4f Mon Sep 17 00:00:00 2001
From: Gemini Lasswell <gazally <at> runbox.com>
Date: Wed, 20 Sep 2017 10:17:35 -0700
Subject: [PATCH] Fix dynamic binding wrapper in iter-lambda (bug#25965)

* lisp/emacs-lisp/generator.el (cps--make-dynamic-binding-wrapper):
Remove extra evaluation of form.
* test/lisp/emacs-lisp/generator-tests.el
(cps-iter-lambda-with-dynamic-binding): New test.
---
 lisp/emacs-lisp/generator.el            |  3 +--
 test/lisp/emacs-lisp/generator-tests.el | 10 ++++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lisp/emacs-lisp/generator.el b/lisp/emacs-lisp/generator.el
index f3597cc387..3e9885900c 100644
--- a/lisp/emacs-lisp/generator.el
+++ b/lisp/emacs-lisp/generator.el
@@ -142,8 +142,7 @@ cps--make-dynamic-binding-wrapper
     `(let ((,dynamic-var ,static-var))
        (unwind-protect ; Update the static shadow after evaluation is done
             ,form
-         (setf ,static-var ,dynamic-var))
-       ,form)))
+         (setf ,static-var ,dynamic-var)))))
 
 (defmacro cps--with-dynamic-binding (dynamic-var static-var &rest body)
   "Evaluate BODY such that generated atomic evaluations run with
diff --git a/test/lisp/emacs-lisp/generator-tests.el b/test/lisp/emacs-lisp/generator-tests.el
index 4cc6c841da..cbb136ae91 100644
--- a/test/lisp/emacs-lisp/generator-tests.el
+++ b/test/lisp/emacs-lisp/generator-tests.el
@@ -282,3 +282,13 @@ cps-test-closed-flag
 (ert-deftest cps-test-declarations-preserved ()
   (should (equal (documentation 'generator-with-docstring) "Documentation!"))
   (should (equal (get 'generator-with-docstring 'lisp-indent-function) 5)))
+
+(ert-deftest cps-iter-lambda-with-dynamic-binding ()
+  "`iter-lambda' with dynamic binding produces correct result (bug#25965)."
+  (should (= 1
+             (iter-next
+              (funcall (iter-lambda ()
+                         (let* ((fill-column 10) ;;any special variable will do
+                                (i 0)
+                                (j (setq i (1+ i))))
+                           (iter-yield i))))))))
-- 
2.14.1

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