Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:102625
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmx.de designates 212.227.15.19 as permitted sender)
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: PHP internals <internals@lists.php.net>
References: <e21e7c17-4a1a-fba8-5e84-5b9de60a9846@gmx.de>
 <CAF+90c8N8iymvHSLFDAFVyHG_NAr=s3Savxz9+VtKxzwT9SwNA@mail.gmail.com>
Message-ID: <f5d10ce9-deb8-19db-8a29-243d70f124f5@gmx.de>
Date: Fri, 6 Jul 2018 17:21:09 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.8.0
MIME-Version: 1.0
In-Reply-To: <CAF+90c8N8iymvHSLFDAFVyHG_NAr=s3Savxz9+VtKxzwT9SwNA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: de-DE
Content-Transfer-Encoding: 8bit
Subject: Re: [PHP-DEV] Z_CACHE_SLOT changed meaning in PHP 7.3?
From: cmbecker69@gmx.de ("Christoph M. Becker")

On 06.07.2018 at 15:55, Nikita Popov wrote:

> On Fri, Jul 6, 2018 at 3:38 PM, Christoph M. Becker <cmbecker69@gmx.de>
> wrote:
>
>> While trying to put together a patch to make PECL/uopz compatible with
>> PHP 7.3[1], I've stumbled upon commit ca035f2[2] and commit 1a63fa6[3].
>> The former removed Z_CACHE_SLOT and related stuff, but the latter
>> reintroduced it with an apparently somewhat different meaning.  If that
>> is correct, this change should be documented in UPGRADING.INTERNALS, and
>> perhaps it might even be better to rename the RECV_INIT cache and the
>> related macros, so any extension (probably few, if any) would already
>> fail at compile time.
>>
>> [1] <https://github.com/krakjoe/uopz/issues/79>
>> [2]
>> <http://git.php.net/?p=php-src.git;a=commit;h=
>> ca035f26aa296acf553f289e2d459fd052367db2>
>> [3]
>> <http://git.php.net/?p=php-src.git;a=commit;h=
>> 1a63fa6ec9b0bacbb726e60c3c212e7d97b518c6>
> 
> The meaning of Z_CACHE_SLOT is still the same (cache slot stored in u2 of
> literal). The thing that changed is that we now prefer storing the cache
> slot directly on the opline, if possible. RECV_INIT is one of the cases
> where two independent cache slots are needed, one is stored on the opline
> and the other in Z_CACHE_SLOT of the initializer expression literal.

Thanks!  However, the fact that the cache slot is now preferably stored
on the opline (extended_value) is an issue for PECL/uopz.  For instance,
running the following script with uopz enabled

  <?php
  function foo() {}
  foo();

makes valgrind report an “Use of uninitialised value of size 8”[1], and
obviously this code doesn't do anymore what it is supposed to do:

  CACHE_PTR(Z_CACHE_SLOT_P(function_name), NULL);

[1]
<https://gist.github.com/cmb69/3060a552fc825497d066262ab31f3998#file-0001-update-for-php-7-3-patch-L43>

-- 
Christoph M. Becker