Description:
------------
The test script below does not leak, but if $a were to successfully load class "foo" (i.e. move the eval() in $b() into $a) it leaks memory in zend_execute.c on line 723, which is the portion called when the closure is assigned to $b.

This is caused by 2 separate bugs.

1) php_spl.c line 501 increases the refcount of the closure zval
2) php_spl.c line 511 checks to see if the function name has already been registered, but treats all closures as if they were "closure::__invoke" instead of using some unique aspect of each closure.  This then jumps to the end of spl_autoload_register without decreasing the refcount, and boom, we have a memory leak.

I don't know anything about the closures implementation, so someone who knows a better way to get a unique function name for a closure needs to fix this, both the refcount and the only-one-closure-allowed issues.

Also, the memory leak is triggered by an important feature of Pyrus, and yes, we are registering multiple closures as autoload callbacks to implement a dynamic plugin system.  It works great except for these two bugs.

Reproduce code:
---------------
<?php
$a = function ($class) {
    echo "a called\n";
};
$b = function ($class) {
    eval('class ' . $class . '{}');
    echo "b called\n";
};
spl_autoload_register($a);
spl_autoload_register($b);
$c = new foo;


Expected result:
----------------
a called
b called

Actual result:
--------------
a called

Fatal error: Class 'foo' not found in /home/user/workspace/php5/test.php on line 11

Call Stack:
    0.0005     345172   1. {main}() /home/user/workspace/php5/test.php:0