Subject: bug#13543: 24.2; [PATCH] (ert) "wrong-type-argument characterp" when assert fail on large (>28 bit) numbers

From: Oleksandr Gavenko <[email-masked]>
Date: Thu, 24 Jan 2013 22:32:35 +0200

In GNU Emacs 24.2.1 (x86_64-pc-linux-gnu, GTK+ Version 2.24.10)
 of 2012-09-09 on trouble, modified by Debian

'should' from lisp/emacs-lisp/ert.el fail to create character from number, for
example evaluate one of these expressions:

  (should (equal #x1000000 1))
  (should (equal 1 -1))

Problem come from "?%c" in:

  (defun ert--explain-format-atom (x)
    "Format the atom X for `ert--explain-equal'."
    (typecase x
      (fixnum (list x (format "#x%x" x) (format "?%c" x)))
      (t x)))

Another problem from (format "?%c" x) is performance penalty when "x" is rare
character code (font library intensively scan for missing character glyph
among all system available fonts causing 5 second delay and 100% hard disk
usage).

I recommend remove formatting to character as amount of problems are larger
then amount of benefits.

I discover this issue when start write tests for low level binary parsing
library (ASN.1).

=== modified file 'lisp/ChangeLog'
--- lisp/ChangeLog	2012-12-19 13:01:16 +0000
+++ lisp/ChangeLog	2013-01-24 20:29:45 +0000
@@ -1,3 +1,10 @@
+2013-01-24  Oleksandr Gavenko  <[email-masked]>
+
+	* ert.el (ert--explain-format-atom): Delete formating into
+	character due to performance issue on attempts to find font glyph
+	for rare used character and impossibility handle negative or large
+	numbers.
+
 2012-12-19  Michael Albinus  <[email-masked]>
 
 	* net/tramp-sh.el (tramp-sh-handle-file-acl): Delete empty lines

=== modified file 'lisp/emacs-lisp/ert.el'
--- lisp/emacs-lisp/ert.el	2012-11-23 03:26:09 +0000
+++ lisp/emacs-lisp/ert.el	2013-01-24 20:21:48 +0000
@@ -568,7 +568,7 @@
 (defun ert--explain-format-atom (x)
   "Format the atom X for `ert--explain-equal'."
   (cl-typecase x
-    (fixnum (list x (format "#x%x" x) (format "?%c" x)))
+    (fixnum (list x (format "#x%x" x)))
     (t x)))
 
 (defun ert--explain-equal-rec (a b)

-- 
Best regards!