Re: transpose-regions

[Chong Yidong]

I've narrowed down the location where the interval plist becomes
invalid.  I patched Ftranspose_regions in editfns.c as follows:

*** emacs/src/editfns.c.~1.436.~        2007-03-17 15:00:52.000000000 -0400
--- emacs/src/editfns.c 2007-03-23 11:31:06.000000000 -0400
***************
*** 4031,4036 ****
--- 4031,4038 ----
  
     It's the caller's job to ensure that START1 <= END1 <= START2 <= END2.  */
  
+ extern Lisp_Object Vdead;
+ 
  static void
  transpose_markers (start1, end1, start2, end2,
                   start1_byte, end1_byte, start2_byte, end2_byte)
***************
*** 4224,4232 ****
--- 4226,4245 ----
  
        tmp_interval1 = copy_intervals (cur_intv, start1, len1);
        tmp_interval2 = copy_intervals (cur_intv, start2, len2);
+ 
+       if (! NULL_INTERVAL_P (tmp_interval1)
+         && CONSP (tmp_interval1->plist)
+         && EQ (XCAR (tmp_interval1->plist), Vdead))
+       abort();
+ 
        Fset_text_properties (make_number (start1), make_number (end2),
                            Qnil, Qnil);
  
+       if (! NULL_INTERVAL_P (tmp_interval1)
+         && CONSP (tmp_interval1->plist)
+         && EQ (XCAR (tmp_interval1->plist), Vdead))
+       abort();
+ 
        /* First region smaller than second.  */
        if (len1_byte < len2_byte)
          {

Using Martin's recipe, I obtained the following backtrace:

#0  abort () at emacs.c:431
#1  0x081af617 in Ftranspose_regions (startr1=104688, endr1=105304, 
    startr2=105304, endr2=105648, leave_markers=137955529) at editfns.c:4241
...

Line 4241 corresponds to the second abort() statement, which means the
plist in tmp_interval1 got garbage collected during the call to
Fset_text_properties.  It looks like Fset_text_properties makes
changes to intervals in the buffer; probably this invalidates the
plist in tmp_interval1 in some way.