GNU bug report logs - #5082
23.1.50; print-circle and make-hash-table

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: 川幡太一 <kawabata.taichi <at> gmail.com>
To: emacs-pretest-bug <at> gnu.org
Subject: 23.1.50; print-circle and make-hash-table
Date: Tue, 1 Dec 2009 00:09:30 +0900

Dear Emacs Developers,

I've found an Emacs behavior that seems a bug concerning to `print-circle'
and make-hash-table, so I would like to report it.

By setting `print-circle' to `t', printing Lisp Object with recursive
or repetitive
list should be displayed as #N= and #N# syntax.

However, it seems this is not true when printing lisp objects within
hash tables
(which become possible in Emacs 23.1.50.)  Following is an example.

Is it possible to display the repetitive lisp object within printed hash tables
by #N= and #N# syntax, when `print-circle' is set to `t'?

I notify this behavior as a bug, but it may not be so.  I apologize in that
case.

(let ((print-circle t)
      (x (list 10 20))
      (y (make-hash-table)))
  (insert (format "%S\n" (list x x)))
  (puthash 1 x y)
  (puthash 2 x y)
  (insert (format "%S\n" y))
  (setcar x 3)
  (insert (format "%S\n" y)))

Result:
> (#1=(10 20) #1#)
> #s(hash-table size 65 test eql rehash-size 1.5 rehash-threshold 0.8
> data (1 (10 20) 2 (10 20)))
> #s(hash-table size 65 test eql rehash-size 1.5 rehash-threshold 0.8
> data (1 (3 20) 2 (3 20)))
nil

Cordially Yours,

-- 
---------------------------------------------------------------------
　KAWABATA, Taichi　　　E-mail: kawabata.taichi <at> gmail.com

Message #10 received at 5082-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: 川幡太一 <kawabata.taichi <at> gmail.com>
Subject: Re: bug#5082: 23.1.50; print-circle and make-hash-table
Date: Mon, 30 Nov 2009 16:08:38 -0500

> I've found an Emacs behavior that seems a bug concerning to `print-circle'
> and make-hash-table, so I would like to report it.

Thanks for catching this bug and for the clear testcase.  I've installed
the patch below which should fix it.


        Stefan


=== modified file 'src/print.c'
--- src/print.c	2009-11-24 15:30:54 +0000
+++ src/print.c	2009-11-30 21:03:36 +0000
@@ -1420,6 +1420,13 @@
 	    size &= PSEUDOVECTOR_SIZE_MASK;
 	  for (i = 0; i < size; i++)
 	    print_preprocess (XVECTOR (obj)->contents[i]);
+	  if (HASH_TABLE_P (obj))
+	    { /* For hash tables, the key_and_value slot is past
+	        `size' because it needs to be marked specially in case
+	        the table is weak.  */
+	      struct Lisp_Hash_Table *h = XHASH_TABLE (obj);
+	      print_preprocess (h->key_and_value);
+	    }
 	  break;
 
 	default:

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