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Re: [bug] Vim-7.3a crashes with persistent undo and autocmd FileChangedRO

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  • Dominique Pellé
    ... You re right. I now see that it also happens with Vim-7.2.444. The way to reproduce it has to be different though. Following command crashes with both
    Message 1 of 3 , Jul 1, 2010
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      Bram Moolenaar wrote:

      > Dominique Pelle wrote:
      >
      >> Vim-7.3a (2278:e41433ea71df) crashed while I was using undo.
      >> It happened when doing undo on a file which was read-only
      >> in perforce (not checked-out).  The Vim perforce plugin has
      >> a FileChangedRO autocommand to automatically check-out
      >> a file when attempting to change it. It causes a crash when
      >> using persistent undo.
      >>
      >> I found a simpler way to reproduce it without using the perforce
      >> Plugin. The following script is enough to cause Vim to crash:
      >>
      >> =========================================================
      >>  #!/bin/sh
      >>
      >> cd /tmp
      >> rm -f foobar foobar.undo
      >> vim -u NONE -N foobar \
      >>   -c ':call feedkeys("aFOO\<Esc>:wundo! foobar.undo\<CR>:wq\<CR>")'
      >> chmod a-w foobar
      >>
      >> # Vim-7.3a (2278:e41433ea71df) will crash here.
      >> vim -u NONE -N foobar \
      >>   -c 'au FileChangedRO * :e!' \
      >>   -c 'rundo foobar.undo' \
      >>   -c 'undo'
      >> =========================================================
      >>
      >> Valgrind gives the following error (in the 2nd invocation of Vim):
      >>
      >> ==2892== Invalid read of size 4
      >> ==2892==    at 0x81C2FC1: u_freeentry (undo.c:3063)
      >> ==2892==    by 0x81C2F78: u_freeentries (undo.c:3044)
      >> ==2892==    by 0x81C2E55: u_freeheader (undo.c:2985)
      >> ==2892==    by 0x81C32E9: u_blockfree (undo.c:3173)
      >> ==2892==    by 0x8053C98: buf_freeall (buffer.c:579)
      >> ==2892==    by 0x8098C37: do_ecmd (ex_cmds.c:3573)
      >> ==2892==    by 0x80AF21E: do_exedit (ex_docmd.c:7626)
      >> ==2892==    by 0x80AEEDB: ex_edit (ex_docmd.c:7522)
      >> ==2892==    by 0x80A7AB8: do_one_cmd (ex_docmd.c:2640)
      >> ==2892==    by 0x80A5391: do_cmdline (ex_docmd.c:1109)
      >> ==2892==    by 0x80CE2CC: apply_autocmds_group (fileio.c:9334)
      >> ==2892==    by 0x80CDCDE: apply_autocmds (fileio.c:8943)
      >> ==2892==    by 0x810C467: change_warning (misc1.c:2995)
      >> ==2892==    by 0x810B78C: changed (misc1.c:2493)
      >> ==2892==    by 0x810BC8D: changed_common (misc1.c:2747)
      >> ==2892==    by 0x810BBA1: changed_lines (misc1.c:2692)
      >> ==2892==    by 0x81C2082: u_undoredo (undo.c:2487)
      >> ==2892==    by 0x81C127B: u_doit (undo.c:1962)
      >> ==2892==    by 0x81C112F: u_undo (undo.c:1907)
      >> ==2892==    by 0x80B0594: ex_undo (ex_docmd.c:8466)
      >> ==2892==    by 0x80A7AB8: do_one_cmd (ex_docmd.c:2640)
      >> ==2892==    by 0x80A5391: do_cmdline (ex_docmd.c:1109)
      >> ==2892==    by 0x80A4A4B: do_cmdline_cmd (ex_docmd.c:715)
      >> ==2892==    by 0x80EA19E: exe_commands (main.c:2755)
      >> ==2892==    by 0x80E7955: main (main.c:880)
      >> ==2892==  Address 0x4fc017c is 4 bytes inside a block of size 8 free'd
      >> ==2892==    at 0x4024B8A: free (vg_replace_malloc.c:366)
      >> ==2892==    by 0x8116ED6: vim_free (misc2.c:1702)
      >> ==2892==    by 0x81C1F9F: u_undoredo (undo.c:2473)
      >> ==2892==    by 0x81C127B: u_doit (undo.c:1962)
      >> ==2892==    by 0x81C112F: u_undo (undo.c:1907)
      >> ==2892==    by 0x80B0594: ex_undo (ex_docmd.c:8466)
      >> ==2892==    by 0x80A7AB8: do_one_cmd (ex_docmd.c:2640)
      >> ==2892==    by 0x80A5391: do_cmdline (ex_docmd.c:1109)
      >> ==2892==    by 0x80A4A4B: do_cmdline_cmd (ex_docmd.c:715)
      >> ==2892==    by 0x80EA19E: exe_commands (main.c:2755)
      >> ==2892==    by 0x80E7955: main (main.c:880)
      >> (several more errors after that)
      >>
      >> Source of src/undo.c:
      >>
      >> 2458   /* insert the lines in u_array between top and bot */
      >> 2459   if (newsize)
      >> 2460   {
      >> 2461       for (lnum = top, i = 0; i < newsize; ++i, ++lnum)
      >> 2462       {
      >> 2463           /*
      >> 2464            * If the file is empty, there is an empty line 1 that we
      >> 2465            * should get rid of, by replacing it with the new line
      >> 2466            */
      >> 2467           if (empty_buffer && lnum == 0)
      >> 2468               ml_replace((linenr_T)1, uep->ue_array[i], TRUE);
      >> 2469           else
      >> 2470               ml_append(lnum, uep->ue_array[i], (colnr_T)0, FALSE);
      >> 2471           vim_free(uep->ue_array[i]);
      >> 2472       }
      >> 2473       vim_free((char_u *)uep->ue_array);  <--- MEMORY IS FREED
      >> 2474   }
      >> 2475
      >> 2476   /* adjust marks */
      >> 2477   if (oldsize != newsize)
      >> 2478   {
      >> 2479       mark_adjust(top + 1, top + oldsize, (long)MAXLNUM,
      >> 2480                                          (long)newsize - (long)oldsize);
      >> 2481       if (curbuf->b_op_start.lnum > top + oldsize)
      >> 2482           curbuf->b_op_start.lnum += newsize - oldsize;
      >> 2483       if (curbuf->b_op_end.lnum > top + oldsize)
      >> 2484           curbuf->b_op_end.lnum += newsize - oldsize;
      >> 2485   }
      >> 2486
      >> 2487   changed_lines(top + 1, 0, bot, newsize - oldsize); <--- USE FREE MEM
      >>
      >> Not sure how to fix it yet,
      >
      > Was this actually changed during the recent undo feature changes?
      > No, Vim 7.2 has the same code.  Thus it's actually an old problem.


      You're right. I now see that it also happens with Vim-7.2.444.
      The way to reproduce it has to be different though.
      Following command crashes with both Vim-7.2.444 and
      Vim-7.3a (2278:e41433ea71df):

      $ rm foobar .foobar* ; ./vim -u NONE -N foobar \
      -c 'au FileChangedRO * e!' \
      -c 'norm iFOO' \
      -c 'set ro' \
      -c 'undo|redo'
      Segmentation fault (core dumped)

      -- Dominique

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