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Bug #49194 var_dump() doesn't completely protect against infinite looping
Submitted: 2009-08-07 18:44 UTC Modified: 2009-08-10 15:19 UTC
From: gwynne@php.net Assigned: colder (profile)
Status: Closed Package: *General Issues
PHP Version: 5.3, 6 (2009-08-07) OS: *
Private report: No CVE-ID: None
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 [2009-08-07 18:44 UTC] gwynne@php.net 
Description:
------------
Calling var_dump() on a closure that references itself results in an infinite loop.

Reproduce code:
---------------
<?php
$f = function () use (&$f) {};
var_dump($f);
?>

Expected result:
----------------
object(Closure)#1 (1) {
  ["static"]=>
  array(1) {
    ["f"]=>
    &object(Closure)#1 (1) {
      ["static"]=>
      array(1) {
        ["f"]=>RECURSION
      }
    }
  }
}

Actual result:
--------------
object(Closure)#1 (1) {
  ["static"]=>
  array(1) {
    ["f"]=>
    &object(Closure)#1 (1) {
      ["static"]=>
      array(1) {
        ["f"]=>
        &object(Closure)#1 (1) {
          ["static"]=>
          array(1) {
            ["f"]=>
<repeats forever>

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 [2009-08-07 20:33 UTC] colder@php.net 
This is an inherent problem of the get_debug_info handler.

For closures which should (I guess) remain constant across multiple var_dump calls, there is an easy solution of caching the HT.

http://patches.colder.ch/php-src/zend_closures_recursion-5.3.patch?markup

However, multiple mutable classes uses a custom debug_info handler with full control over the items, such as SPLDoublyLinkedList. The problem here seems to be impossible to fix without adapting the get_debug_info handler.

Changing it from 

HashTable *(*zend_object_get_debug_info_t)(zval *object, int *is_temp TSRMLS_DC);

to 

HashTable **(*zend_object_get_debug_info_t)(zval *object, int *is_temp TSRMLS_DC);

should be sufficient.
 [2009-08-10 15:19 UTC] colder@php.net 
This bug has been fixed in SVN.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

Found another solution which do not imply an API break.
 
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