odd assertion in gtktextiter.c

[Skip Montanaro <skip pobox com>]

I'm getting an assertion error in forward_line_leaving_caches_unmodified in
gtktextiter.c (this is from the vanilla 1.3.5 distribution).  There is a
test of new_line:

  if (new_line != NULL)
    {
    ... do some stuff ...
    }
  else
    {
      /* There is no way to move forward; we were already
         at the "end" index. (the end index is the last
         line pointer, segment_byte_offset of 0) */

      g_assert (real->line_char_offset == 0 ||
                real->line_byte_offset == 0);
    ... do some other stuff ...
    }

I'm landing in the else clause.  The assertion is failing because
real_line_char_offset is -1 and real->line_byte_offset is 25.  I looked at
new_line and discovered its value to be 0xffffffff.  So my confusion is
two-fold.  One, new_line's value looks mighty suspicious to me.  (Looks like
-1 instead of a valid pointer.)  Two, how in the heck could new_line have
compared equal to NULL?  I don't believe I did anything unusual when
compiling Gtk, so the gcc compilation flags where probably just "-g -O2".
I'll try rebuilding without any optimization and see if that helps.  Any
other debugging suggestions would be appreciated.

Thanks,

-- 
Skip Montanaro (skip pobox com)
(847)971-7098