`eval` is leaking memory

Description

The following code:

<?php

$m = memory_get_usage();
for ($i = 0; $i < 1000; $i++) {
    $fn = eval('return function ($foo) {};');
    //$fn = function ($foo) {};
    var_dump(memory_get_usage() - $m);
}

https://3v4l.org/LF4Ri
https://3v4l.org/1DeC6 - /wo eval, not leaking
https://3v4l.org/NtIrU - eval /wo anonymous function is not leaking

Resulted in this output:

int(640)
int(672)
int(672)
int(672)
...
int(197280)

But I expected this output instead:

int(640)
int(672)
int(672)
int(672)
...
int(672)

PHP Version

8.1.x

Operating System

any

首先运行提供的 PHP 8.1 重现代码，并将其内存使用情况与 issue 中链接的 direct-closure 和 eval-without-anonymous-function 示例进行比较。跟踪负责创建匿名函数的 eval 路径；当重复求值不再显示内存使用量持续增加时，即表示完成。