* syntax.c (skip_chars): Don't use uninitialized storage

when searching a multibyte buffer for characters that are not in a
unibyte string that contains non-ASCII characters.

1 files changed, 21 insertions, 24 deletions

diff --git a/src/syntax.c b/src/syntax.c
index 390d732944d..1b76f56dea6 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -1577,34 +1577,31 @@ skip_chars (int forwardp, Lisp_Object string, Lisp_Object lim, int handle_iso_cl
          the corresponding multibyte chars.  */
       if (multibyte && string_has_eight_bit)
         {
-          unsigned char fastmap2[0400];
-          int range_start_byte, range_start_char;
-
-          memcpy (fastmap + 0200, fastmap2 + 0200, 0200);
+          char *p1;
+          char himap[0200 + 1];
+          memcpy (himap, fastmap + 0200, 0200);
+          himap[0200] = 0;
           memset (fastmap + 0200, 0, 0200);
-          /* We are sure that this loop stops.  */
-          for (i = 0200; ! fastmap2[i]; i++);
-          c = BYTE8_TO_CHAR (i);
-          fastmap[CHAR_LEADING_CODE (c)] = 1;
-          range_start_byte = i;
-          range_start_char = c;
           char_ranges = alloca (sizeof *char_ranges * 128 * 2);
-          for (i = 129; i < 0400; i++)
+          i = 0;
+
+          while ((p1 = memchr (himap + i, 1, 0200 - i)))
             {
-              c = BYTE8_TO_CHAR (i);
-              fastmap[CHAR_LEADING_CODE (c)] = 1;
-              if (i - range_start_byte != c - range_start_char)
-                {
-                  char_ranges[n_char_ranges++] = range_start_char;
-                  char_ranges[n_char_ranges++] = ((i - 1 - range_start_byte)
-                                                  + range_start_char);
-                  range_start_byte = i;
-                  range_start_char = c;
-                }
+              /* Deduce the next range C..C2 from the next clump of 1s
+                 in HIMAP starting with &HIMAP[I].  HIMAP is the high
+                 order half of the old FASTMAP.  */
+              int c2, leading_code;
+              i = p1 - himap;
+              c = BYTE8_TO_CHAR (i + 0200);
+              i += strlen (p1);
+              c2 = BYTE8_TO_CHAR (i + 0200 - 1);
+
+              char_ranges[n_char_ranges++] = c;
+              char_ranges[n_char_ranges++] = c2;
+              leading_code = CHAR_LEADING_CODE (c);
+              memset (fastmap + leading_code, 1,
+                      CHAR_LEADING_CODE (c2) - leading_code + 1);
             }
-          char_ranges[n_char_ranges++] = range_start_char;
-          char_ranges[n_char_ranges++] = ((i - 1 - range_start_byte)
-                                          + range_start_char);
         }
     }
   else                          /* STRING is multibyte */