GNU bug report logs - #8600
struct charset.code_space[15] contains garbage

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From: Paul Eggert <eggert <at> cs.ucla.edu>
To: 8600 <at> debbugs.gnu.org
Subject: bug#8600: struct charset.code_space[15] contains garbage
Date: Sun, 01 May 2011 09:59:25 -0700

While testing the 32+64 port I noticed that a too-wide value
is stuffed into charset.code_space[15], which means that
slot has a garbage value (at least, it's garbage on typical
machines with 32-bit int).  As far as I can see, the garbage
value is never used, so it's a bit cleaner to never compute
or store it.

I plan to install the following patch to do that.
This patch is relevant to ordinary 32- and 64-bit hosts, too,
so I'm separating it out.

* charset.h (struct charset.code_space): Now has 15 elements, not 16.
* charset.c (Fdefine_charset_internal): Don't initialize
charset.code_space[15].  The value was garbage, on hosts with
32-bit int.
=== modified file 'src/charset.c'
--- src/charset.c	2011-04-26 06:17:52 +0000
+++ src/charset.c	2011-05-01 06:28:23 +0000
@@ -869,7 +869,7 @@
   ASET (attrs, charset_name, args[charset_arg_name]);

   val = args[charset_arg_code_space];
-  for (i = 0, dimension = 0, nchars = 1; i < 4; i++)
+  for (i = 0, dimension = 0, nchars = 1; ; i++)
     {
       int min_byte, max_byte;

@@ -880,10 +880,12 @@
       charset.code_space[i * 4] = min_byte;
       charset.code_space[i * 4 + 1] = max_byte;
       charset.code_space[i * 4 + 2] = max_byte - min_byte + 1;
+      if (max_byte > 0)
+	dimension = i + 1;
+      if (i == 3)
+	break;
       nchars *= charset.code_space[i * 4 + 2];
       charset.code_space[i * 4 + 3] = nchars;
-      if (max_byte > 0)
-	dimension = i + 1;
     }

   val = args[charset_arg_dimension];

=== modified file 'src/charset.h'
--- src/charset.h	2011-04-11 06:48:18 +0000
+++ src/charset.h	2011-05-01 16:22:33 +0000
@@ -155,10 +155,11 @@
      byte code of the (N+1)th dimension, <code_space>[4N+1] is a
      maximum byte code of the (N+1)th dimension, <code_space>[4N+2] is
      (<code_space>[4N+1] - <code_space>[4N] + 1), <code_space>[4N+3]
-     is a number of characters containd in the first to (N+1)th
-     dismesions.  We get `char-index' of a `code-point' from this
+     is the number of characters contained in the first through (N+1)th
+     dimensions, except that there is no <code_space>[15].
+     We get `char-index' of a `code-point' from this
      information.  */
-  int code_space[16];
+  int code_space[15];

   /* If B is a byte of Nth dimension of a code-point, the (N-1)th bit
      of code_space_mask[B] is set.  This array is used to quickly

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