function processListItems (listStr, trimTrailing) {
    // The $g_list_level global keeps track of when we're inside a list.
    // Each time we enter a list, we increment it; when we leave a list,
    // we decrement. If it's zero, we're not in a list anymore.
    //
    // We do this because when we're not inside a list, we want to treat
    // something like this:
    //
    //    I recommend upgrading to version
    //    8. Oops, now this line is treated
    //    as a sub-list.
    //
    // As a single paragraph, despite the fact that the second line starts
    // with a digit-period-space sequence.
    //
    // Whereas when we're inside a list (or sub-list), that line will be
    // treated as the start of a sub-list. What a kludge, huh? This is
    // an aspect of Markdown's syntax that's hard to parse perfectly
    // without resorting to mind-reading. Perhaps the solution is to
    // change the syntax rules such that sub-lists must start with a
    // starting cardinal number; e.g. "1." or "a.".
    globals.gListLevel++;

    // trim trailing blank lines:
    listStr = listStr.replace(/\n{2,}$/, '\n');

    // attacklab: add sentinel to emulate \z
    listStr += '~0';

    var rgx = /(\n)?(^[ \t]*)([*+-]|\d+[.])[ \t]+((\[(x|X| )?])?[ \t]*[^\r]+?(\n{1,2}))(?=\n*(~0|\2([*+-]|\d+[.])[ \t]+))/gm,
        isParagraphed = (/\n[ \t]*\n(?!~0)/.test(listStr));

    listStr = listStr.replace(rgx, function (wholeMatch, m1, m2, m3, m4, taskbtn, checked) {
      checked = (checked && checked.trim() !== '');
      var item = showdown.subParser('outdent')(m4, options, globals),
          bulletStyle = '';

      // Support for github tasklists
      if (taskbtn && options.tasklists) {
        bulletStyle = ' class="task-list-item" style="list-style-type: none;"';
        item = item.replace(/^[ \t]*\[(x|X| )?]/m, function () {
          var otp = '<input type="checkbox" disabled style="margin: 0px 0.35em 0.25em -1.6em; vertical-align: middle;"';
          if (checked) {
            otp += ' checked';
          }
          otp += '>';
          return otp;
        });
      }
      // m1 - Leading line or
      // Has a double return (multi paragraph) or
      // Has sublist
      if (m1 || (item.search(/\n{2,}/) > -1)) {
        item = showdown.subParser('githubCodeBlocks')(item, options, globals);
        item = showdown.subParser('blockGamut')(item, options, globals);
      } else {
        // Recursion for sub-lists:
        item = showdown.subParser('lists')(item, options, globals);
        item = item.replace(/\n$/, ''); // chomp(item)
        if (isParagraphed) {
          item = showdown.subParser('paragraphs')(item, options, globals);
        } else {
          item = showdown.subParser('spanGamut')(item, options, globals);
        }
      }
      item =  '\n<li' + bulletStyle + '>' + item + '</li>\n';
      return item;
    });

    // attacklab: strip sentinel
    listStr = listStr.replace(/~0/g, '');

    globals.gListLevel--;

    if (trimTrailing) {
      listStr = listStr.replace(/\s+$/, '');
    }

    return listStr;
  }
Process the contents of a single ordered or unordered list, splitting it
into individual list items.
@param {string} listStr
@param {boolean} trimTrailing
@returns {string}