[php-src] Issue #22516: zend_alloc bin 0 may leak

[email protected] (ndossche) Mon, 29 Jun 2026 22:01:19 +0000

Newsgroups	php.bugs
Message-ID	<[email protected]>

Issue: https://github.com/php/php-src/issues/22516
Author: ndossche

### Description

Value set analysis shows that `ZEND_MM_SRUN_FREE_COUNTER` macro can return a value in the interval [0, 511].
However, bin 0 from `ZEND_MM_BINS_INFO` has 512 free elements.
So the following check cannot fire:

https://github.com/php/php-src/blob/c1a6258015eca9e3edb768114d13db954ce77a65/Zend/zend_alloc.c#L2196

Found using SAST.

### PHP Version

```plain
master
```

### Operating System

_No response_