Re: scanner / lexer problem in GUI

[Ben Pfaff]

Thanks for investigating and reviewing.  I pushed my patches.

John Darrington <address@hidden> writes:

> OK.  I like your solution better.
>
> Please push it when you're ready.
>
> J'
>
> On Sun, May 06, 2012 at 05:34:48AM +0000, John Darrington wrote:
>      As it happened, I had a prepared a similar patch.  Attached.
>      Perhaps we could compare patches.
>      
>      J'
>      
>      On Sat, May 05, 2012 at 10:14:57PM -0700, Ben Pfaff wrote:
>           John Darrington <address@hidden> writes:
>           
>           > Looking at the bug recently reported on bug-gnu-pspp I notice the 
> following.
>           >
>           > Valgrind reports:
>           
>           I sent out a 2-patch series that fixes the problem that I see,
>           with and without valgrind.  Does it fix the problem you see too?
>           
>           Thanks,
>           
>           Ben.
>      
>      -- 
>      PGP Public key ID: 1024D/2DE827B3 
>      fingerprint = 8797 A26D 0854 2EAB 0285  A290 8A67 719C 2DE8 27B3
>      See http://keys.gnupg.net or any PGP keyserver for public key.
>      
>
>      diff --git a/src/language/lexer/lexer.c b/src/language/lexer/lexer.c
>      index e72a3e4..7048d8a 100644
>      --- a/src/language/lexer/lexer.c
>      +++ b/src/language/lexer/lexer.c
>      @@ -1217,6 +1217,9 @@ lex_source_read__ (struct lex_source *src)
>             n = src->reader->class->read (src->reader, &src->buffer[head_ofs],
>                                           src->allocated - head_ofs,
>                                           segmenter_get_prompt 
> (&src->segmenter));
>      +
>      +      assert (n <= src->allocated - head_ofs);
>      +
>             if (n == 0)
>               {
>                 /* End of input.
>      diff --git a/src/ui/gui/psppire-lex-reader.c 
> b/src/ui/gui/psppire-lex-reader.c
>      index ae043b0..6351094 100644
>      --- a/src/ui/gui/psppire-lex-reader.c
>      +++ b/src/ui/gui/psppire-lex-reader.c
>      @@ -66,26 +66,47 @@ lex_gtk_text_buffer_read (struct lex_reader *r_, 
> char *buf, size_t n,
>                        enum prompt_style prompt_style UNUSED)
>       {
>         struct lex_gtk_text_buffer_reader *r = 
> lex_gtk_text_buffer_reader_cast (r_);
>      -  int n_chars = n;
>         char *s;
>       
>         GtkTextIter iter = r->start ;
>         
>      -  int offset = gtk_text_iter_get_offset (&iter);
>      -  int end_offset = gtk_text_iter_get_offset (&r->stop);
>      -
>      -  if ( end_offset - offset < n)
>      -    n_chars = end_offset - offset;
>      -  
>      -  gtk_text_iter_set_offset (&iter, offset + n_chars);
>      -
>      -  s = gtk_text_iter_get_text (&r->start, &iter);
>      -
>      -  strncpy (buf, s, n_chars);
>      +  const gint offset = gtk_text_iter_get_offset (&iter);
>      +  const gint end_offset = gtk_text_iter_get_offset (&r->stop);
>      +  const gint n_bytes = (end_offset - offset < n) ? end_offset - offset 
> : n;
>      +
>      +  /* We want to get no more than n_bytes from the buffer.
>      +     However, since gtk_text_iter deals in chars, not bytes, we cannot 
> possibly
>      +     set an iter which we know will not fetch too many bytes.  Thus, we 
> start
>      +     by assuming that n_chars == n_bytes and step backwards if we end 
> up fetching
>      +     too many.
>      +   */
>      +  gint n_chars = n_bytes;
>      +  gint backstep = 4;
>      +  gint bytes_read = 0;
>      +  do
>      +    {
>      +      gtk_text_iter_set_offset (&iter, offset + n_chars);
>      +
>      +      s = gtk_text_iter_get_text (&r->start, &iter);
>      +      bytes_read = strlen (s);
>      +      if ( n_chars == 1 && bytes_read > n_bytes)
>      +        {
>      +          g_critical ("Reading a single character returned %d bytes, 
> but only %d bytes"
>      +                      " were requested", bytes_read, n_bytes);
>      +          return 0;
>      +        }
>      +      n_chars -= backstep;
>      +      if ( n_chars < 1)
>      +        n_chars = 1;
>      +      backstep *= 2;
>      +    }
>      +  while (bytes_read > n_bytes);
>      +
>      +  strncpy (buf, s, bytes_read);
>       
>         r->start = iter;
>       
>      -  return strlen (s);
>      +  return bytes_read;
>       }