bug#9389: 23.3.50; unencodable-char-position has buffer relocation problem

[Kazuhiro Ito]

When I start precompiled Windows binary with -Q and evaluate below
code, I have unexpected result.

(with-temp-buffer
  (insert (make-string 16 ?A))
  (insert #x80)
  (unencodable-char-position 1 18 'ctext-unix))

-> 13 (Emacs 23.1)
-> 5  (Emacs 23.3)

If I evaluate it twice, it returns expected result (17).

I think the cause of the problem is similar to bug#9318.
unencodable-char-position uses char_charset(), which could cause a
relocation of buffes.  After using it, pointers must be updated as
needed.


=== modified file 'src/coding.c'
--- src/coding.c        2011-05-09 09:59:23 +0000
+++ src/coding.c        2011-08-27 04:29:23 +0000
@@ -8861,7 +8924,7 @@
   Lisp_Object attrs, charset_list, translation_table;
   Lisp_Object positions;
   int from, to;
-  const unsigned char *p, *stop, *pend;
+  const unsigned char *p, *stop, *pend, *orig;
   int ascii_compatible;
 
   setup_coding_system (Fcheck_coding_system (coding_system), &coding);
@@ -8881,7 +8944,7 @@
          || (ascii_compatible
              && (to - from) == (CHAR_TO_BYTE (to) - (CHAR_TO_BYTE (from)))))
        return Qnil;
-      p = CHAR_POS_ADDR (from);
+      p = orig = CHAR_POS_ADDR (from);
       pend = CHAR_POS_ADDR (to);
       if (from < GPT && to >= GPT)
        stop = GPT_ADDR;
@@ -8918,6 +8981,7 @@
   while (1)
     {
       int c;
+      struct charset *charset;
 
       if (ascii_compatible)
        while (p < stop && ASCII_BYTE_P (*p))
@@ -8931,9 +8995,21 @@
        }
 
       c = STRING_CHAR_ADVANCE (p);
+
+      charset_map_loaded = 0;
+      charset = char_charset (translate_char (translation_table, c),
+                             charset_list, NULL);
+      if (charset_map_loaded && NILP (string))
+       {
+         EMACS_INT offset = CHAR_POS_ADDR (from) - orig;
+         orig += offset;
+         p += offset;
+         pend += offset;
+         stop += offset;
+       }
+
       if (! (ASCII_CHAR_P (c) && ascii_compatible)
-         && ! char_charset (translate_char (translation_table, c),
-                            charset_list, NULL))
+         && ! charset)
        {
          positions = Fcons (make_number (from), positions);
          n--;

-- 
Kazuhiro Ito