(Fsubst_char_in_region): Don't use INC_POS in unibyte

buffers because it looks for multibyte character sequences which
don't exist in unibyte text.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 4e25655f492..12db1a310dd 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -2280,12 +2280,13 @@ Both characters must have the same length of multi-byte form.")
 #define COMBINING_BOTH (COMBINING_BEFORE | COMBINING_AFTER)
   int maybe_byte_combining = COMBINING_NO;
   int last_changed;
+  int multibyte_p = !NILP (current_buffer->enable_multibyte_characters);
 
   validate_region (&start, &end);
   CHECK_NUMBER (fromchar, 2);
   CHECK_NUMBER (tochar, 3);
 
-  if (! NILP (current_buffer->enable_multibyte_characters))
+  if (multibyte_p)
     {
       len = CHAR_STRING (XFASTINT (fromchar), fromstr);
       if (CHAR_STRING (XFASTINT (tochar), tostr) != len)
@@ -2341,7 +2342,10 @@ Both characters must have the same length of multi-byte form.")
           stop = end_byte;
         }
       p = BYTE_POS_ADDR (pos_byte);
-      INC_POS (pos_byte_next);
+      if (multibyte_p)
+        INC_POS (pos_byte_next);
+      else
+        ++pos_byte_next;
       if (pos_byte_next - pos_byte == len
           && p[0] == fromstr[0]
           && (len == 1