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

1 files changed, 24 insertions, 0 deletions

diff --git a/src/editfns.c b/src/editfns.c
index 40f0a51d454..258ce2b2e79 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -2320,6 +2320,11 @@ Use %% to put a single % into the output.")
   /* Nonzero if the output should be a multibyte string,
      which is true if any of the inputs is one.  */
   int multibyte = 0;
+  /* 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;
   unsigned char *this_format;
   int longest_format;
   Lisp_Object val;
@@ -2476,6 +2481,7 @@ Use %% to put a single % into the output.")
 
   /* Scan the format and store result in BUF.  */
   format = XSTRING (args[0])->data;
+  maybe_combine_byte = 0;
   while (format != end)
     {
       if (*format == '%')
@@ -2519,6 +2525,12 @@ Use %% to put a single % into the output.")
                     nchars++;
                   }
 
+              if (p > buf
+                  && multibyte
+                  && *((unsigned char *) p - 1) >= 0x80
+                  && STRING_MULTIBYTE (args[n])
+                  && XSTRING (args[n])->data[0] >= 0xA0)
+                maybe_combine_byte = 1;
               nbytes = copy_text (XSTRING (args[n])->data, p,
                                   STRING_BYTES (XSTRING (args[n])),
                                   STRING_MULTIBYTE (args[n]), multibyte);
@@ -2545,6 +2557,11 @@ Use %% to put a single % into the output.")
               else
                 sprintf (p, this_format, XFLOAT (args[n])->data);
 
+              if (p > buf
+                  && multibyte
+                  && *((unsigned char *) p - 1) >= 0x80
+                  && *((unsigned char *) p) >= 0xA0)
+                maybe_combine_byte = 1;
               this_nchars = strlen (p);
               p += this_nchars;
               nchars += this_nchars;
@@ -2553,6 +2570,11 @@ Use %% to put a single % into the output.")
       else if (STRING_MULTIBYTE (args[0]))
         {
           /* Copy a whole multibyte character.  */
+          if (p > buf
+              && multibyte
+              && *((unsigned char *) p - 1) >= 0x80
+              && *format >= 0xA0)
+            maybe_combine_byte = 1;
           *p++ = *format++;
           while (! CHAR_HEAD_P (*format)) *p++ = *format++;
           nchars++;
@@ -2570,6 +2592,8 @@ Use %% to put a single % into the output.")
         *p++ = *format++, nchars++;
     }
 
+  if (maybe_combine_byte)
+    nchars = multibyte_chars_in_text (buf, p - buf);
   val = make_specified_string (buf, nchars, p - buf, multibyte);
 
   /* If we allocated BUF with malloc, free it too.  */