Krumo side effect: Object vars become references [#1855468]

And.. here is my original motivation for
#1853112: Replacement for Krumo?

I had a strange case where a dpm($node) would change the way that Drupal works.
In one case, the node was rendered by an advanced_forum template. In another case it was rendered by a theme node.tpl.php.
Ouch!

After hours of pain, I can now present sth reproducible:

function testme() {
  $x = new stdClass;
  $x->foo = array('bar');
  $is_reference = _check_ref($x, 'foo');
  dpm($is_reference ? 'yes' : 'no');
  // Let's do it again, to show that the side effect is not caused by repeated _check_ref().
  $is_reference = _check_ref($x, 'foo');
  dpm($is_reference ? 'yes' : 'no');
  dpm($x);
  $is_reference = _check_ref($x, 'foo');
  dpm($is_reference ? 'yes' : 'no');
}

function _check_ref($obj, $key) {
  $orig = $obj->$key;
  $c = clone $obj;
  $c->$key = 'tmp';
  $is_reference = ($obj->$key === $c->$key);
  $c->$key = $orig;
  return $is_reference;
}

Result:
no
no
(krumo output)
yes

Pretty bad, isn't it?

Comments

Comment #1

donquixote CreditAttribution: donquixote commented 30 November 2012 at 21:34

That's on PHP 5.3.5

Comment #2

donquixote CreditAttribution: donquixote commented 30 November 2012 at 21:35

Title:

Crazy reference bug in Krumo

» Krumo side effect: Object vars become references

better title

Comment #3

donquixote CreditAttribution: donquixote commented 30 November 2012 at 21:37

And, just saying, krumong()->dpm() does not have this effect.

EDIT:
I only tested this for objects so far, not for arrays.

Comment #4

donquixote CreditAttribution: donquixote commented 30 November 2012 at 22:31

Update:
- krumo does have this side effect on objects, but not on arrays.
- krumong does not have this side effect, neither for arrays nor for objects.

I suppose there is some PHP 4.x logic in krumo causing this mess.

Comment #5

salvis

he/his

CreditAttribution: salvis commented 2 December 2012 at 16:27

We've seen unexplained odd behavior before, after calls to krumo, and this may well be the cause.

It's rare that it makes a difference, but when it does, it's really nasty!

Thank you for the analysis and for your work in #1853112: Replacement for Krumo?!

Comment #6

ttkaminski CreditAttribution: ttkaminski commented 11 January 2013 at 21:13

Wow, this is a major bug. I just started using dpm() recently and ran into this problem right away. I created a module that displays all forms so that I can easily alter and style them.

function MODULE_form_alter(&$form, &$form_state, $form_id) {
  dpm($form);
}

However, because of this bug, the node fields will become corrupted in the template_preprocess_node() resulting in a corrupt $node object for subsequent preprocess_node hooks.

View changes

If it doesn't already, this bug should probably have a higher profile. It seems somewhat serious when one of the primary methods of debugging could cause such unexpected results.