(concat): Pay attention to the byte combining problem.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/fns.c b/src/fns.c
index 6ca612b2153..4d4a2184e15 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -527,6 +527,11 @@ concat (nargs, args, target_type, last_special)
   Lisp_Object last_tail;
   Lisp_Object prev;
   int some_multibyte;
+  /* When we make a multibyte string, we must pay attention to the
+     byte combining problem, i.e., a byte may be combined with a
+     multibyte charcter of the previous string.  This flag tells if we
+     must consider such a situation or not.  */
+  int maybe_combine_byte;
 
   /* In append, the last arg isn't treated like the others */
   if (last_special && nargs > 0)
@@ -636,6 +641,7 @@ concat (nargs, args, target_type, last_special)
 
   prev = Qnil;
 
+  maybe_combine_byte = 0;
   for (argnum = 0; argnum < nargs; argnum++)
     {
       Lisp_Object thislen;
@@ -659,6 +665,11 @@ concat (nargs, args, target_type, last_special)
           int thislen_byte = STRING_BYTES (XSTRING (this));
           bcopy (XSTRING (this)->data, XSTRING (val)->data + toindex_byte,
                  STRING_BYTES (XSTRING (this)));
+          if (some_multibyte
+              && toindex_byte > 0
+              && XSTRING (val)->data[toindex_byte - 1] >= 0x80
+              && XSTRING (this)->data[0] >= 0xA0)
+            maybe_combine_byte = 1;
           toindex_byte += thislen_byte;
           toindex += thisleni;
         }
@@ -731,6 +742,11 @@ concat (nargs, args, target_type, last_special)
                 CHECK_NUMBER (elt, 0);
                 if (SINGLE_BYTE_CHAR_P (XINT (elt)))
                   {
+                    if (some_multibyte
+                        && toindex_byte > 0
+                        && XSTRING (val)->data[toindex_byte - 1] >= 0x80
+                        && XINT (elt) >= 0xA0)
+                      maybe_combine_byte = 1;
                     XSTRING (val)->data[toindex_byte++] = XINT (elt);
                     toindex++;
                   }
@@ -755,6 +771,12 @@ concat (nargs, args, target_type, last_special)
   if (!NILP (prev))
     XCONS (prev)->cdr = last_tail;
 
+  if (maybe_combine_byte)
+    /* Characater counter of the multibyte string VAL may be wrong
+       because of byte combining problem.  We must re-calculate it.  */
+    XSTRING (val)->size = multibyte_chars_in_text (XSTRING (val)->data,
+                                                   XSTRING (val)->size_byte);
+
   return val;
 }