Re: [screen-devel] [bug #60030] Screen segfaults by displaying some UTF-8 character combination

[Michael Schroeder]

On Thu, Feb 11, 2021 at 11:39:09PM +0100, Axel Beckert wrote:
> The only thing it didn't fix so far is
> https://savannah.gnu.org/bugs/?31336 aka
> https://bugs.debian.org/600246 although I really had some hope that
> this might be fixed as a side-effect of your patch. :-)

Oh, that happens because the U+3099 combining char is also matched
in utf8_isdouble(). The code in ansi.c does not expect this. Thus
this is another fallout from that commit. ;)

A simple fix (other than removing the entries from the isdouble
table) is to move the curr->w_mbcs = 0xff setting after the
combining character handling:

diff --git a/ansi.c b/ansi.c
index 2a52edd..83b266d 100644
--- a/ansi.c
+++ b/ansi.c
@@ -692,10 +692,6 @@ register int len;
                    }
                  curr->w_rend.font = 0;
                }
-#  ifdef DW_CHARS
-             if (curr->w_encoding == UTF8 && utf8_isdouble(c))
-               curr->w_mbcs = 0xff;
-#  endif
              if (curr->w_encoding == UTF8 && c >= 0x0300 && utf8_iscomb(c))
                {
                  int ox, oy;
@@ -730,6 +726,10 @@ register int len;
                    }
                  break;
                }
+#  ifdef DW_CHARS
+             if (curr->w_encoding == UTF8 && utf8_isdouble(c))
+               curr->w_mbcs = 0xff;
+#  endif
              font = curr->w_rend.font;
 # endif
 # ifdef DW_CHARS

Cheers,
  Michael.

-- 
Michael Schroeder          SUSE Software Solutions Germany GmbH
mls@suse.de      GF: Felix Imendoerffer HRB 36809, AG Nuernberg
main(_){while(_=~getchar())putchar(~_-1/(~(_|32)/13*2-11)*13);}