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57528[bug] Vim-7.3a crashes with persistent undo and autocmd FileChangedRO

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  • Dominique PellĂ©
    Jul 1, 2010
      Hi

      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,

      -- Dominique

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