Function print_objects_tree

deps/v8/tools/windbg.js:492–535

(root, depth_limit)

// This function assumes the pointer fields to be ptr-size aligned.
function print_objects_tree(root, depth_limit) {
  if(!is_likely_object(root)) {
    print(`${hex(root)} doesn't look like an object`);
    return;
  }

  let path = [];

  function impl(obj, depth, depth_limit) {
    const ptr_size = tagged_size();
    // print the current object and its map pointer
    const this_obj =
      `${" ".repeat(2 * depth)}${hex(obj)} : ${hex(poim(obj - 1))}`;
    const cutoff = depth_limit && depth == depth_limit - 1;
    print(`${this_obj}${cutoff ? " (...)" : ""}`);
    if (cutoff) return;

    path[depth] = obj;
    path.length = depth + 1;
    let cur = obj - 1 + ptr_size;

    // Scan downwards until an address that is likely to be at the start of
    // another object, in which case it's time to pop out from the recursion.
    let iter = 0; // an arbitrary guard to avoid hanging the debugger
    let seen = new Set(path);
    while (!is_likely_object(cur + 1) && iter < 100) {
      iter++;
      let field = poim(cur);
      if (is_likely_object(field)) {
        if (seen.has(field)) {
          print(
            `${" ".repeat(2 * depth + 2)}cycle: ${hex(cur)}->${hex(field)}`);
        }
        else {
          impl(field, depth + 1, depth_limit);
        }
      }
      cur += ptr_size;
    }
  }
  print(`===============================================`);
  impl(root, 0, depth_limit);
  print(`===============================================`);
}

/*-----------------------------------------------------------------------------
    Memory spaces