(INC_POS, DEC_POS): Don't increase or decrease too

much if there's binary code (invalid character code).

1 files changed, 9 insertions, 6 deletions

diff --git a/src/charset.h b/src/charset.h
index d51c6d6f91a..c7c4baecdab 100644
--- a/src/charset.h
+++ b/src/charset.h
@@ -579,11 +579,12 @@ extern int iso_charset_table[2][2][128];
    character boundary.  This macro relies on the fact that *GPT_ADDR
    and *Z_ADDR are always accessible and the values are '\0'.  No
    range checking of POS.  */
-#define INC_POS(pos)                            \
-  do {                                          \
-    unsigned char *p = POS_ADDR (pos) + 1;      \
-    pos++;                                      \
-    while (!CHAR_HEAD_P (p)) p++, pos++;        \
+#define INC_POS(pos)                            \
+  do {                                          \
+    unsigned char *p = POS_ADDR (pos);          \
+    pos++;                                      \
+    if (*p++ >= 0x80)                           \
+      while (!CHAR_HEAD_P (p)) p++, pos++;      \
   } while (0)
 
 /* Decrease the buffer point POS of the current buffer to the previous
@@ -591,11 +592,13 @@ extern int iso_charset_table[2][2][128];
 #define DEC_POS(pos)                                            \
   do {                                                          \
     unsigned char *p, *p_min;                                   \
-    if (--pos < GPT)                                            \
+    int pos_saved = --pos;                                      \
+    if (pos < GPT)                                              \
       p = BEG_ADDR + pos - 1, p_min = BEG_ADDR;                 \
     else                                                        \
       p = BEG_ADDR + GAP_SIZE + pos - 1, p_min = GAP_END_ADDR;  \
     while (p > p_min && !CHAR_HEAD_P (p)) p--, pos--;           \
+    if (*p < 0x80 && pos != pos_saved) pos = pos_saved;         \
   } while (0)
 
 #endif /* emacs */