Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:126241
Precedence: bulk
MIME-Version: 1.0
Date: Thu, 30 Jan 2025 16:50:59 +0100
To: php internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] RFC: Marking return values as important (#[\NoDiscard])
In-Reply-To: <B698F6D0-7EB8-49B8-9638-072B8BE40AC1@cschneid.com>
References: <a995ac24905030e168e7f6006b996cd5@bastelstu.be>
 <a3d14e31-53eb-4a04-8fb2-01f58809fec1@app.fastmail.com>
 <3f170549-cfd6-441e-b892-cf51d726dbe8@bastelstu.be>
 <3b4d9be8-9255-44ab-95c5-ea3045212cf4@app.fastmail.com>
 <B698F6D0-7EB8-49B8-9638-072B8BE40AC1@cschneid.com>
Message-ID: <55641ab50d80b8b375ef9aab296e76b8@bastelstu.be>
Content-Type: text/plain; charset=UTF-8;
 format=flowed
Content-Transfer-Encoding: 8bit
From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

Am 2025-01-29 23:48, schrieb Christian Schneider:
> I guess another option would be to define a
> 	function nop($_) {}
> and then use
> 	nop(outer());
> but my question is whether $_ = outer() and nop(outer()) will be 
> guaranteed to not being optimized in a way which causes the warning to 
> reappear. I don't know much about the optimizations being done but this 
> could be an issue in the future, no?

For `$_` see my reply to Rob. For the function: OPcache will attempt to 
inline functions that only return a (implicit) return statement. However 
this only works if the function is defined in the same file, as OPcache 
currently cannot perform cross-file optimizations. I'd say that defining 
the `nop()` function in a dedicated file is currently the most reliable 
solution to prevent OPcache from optimizing away the usage in a 
backwards-compatible way.

Of course the best solution is actually doing something useful with the 
return value, as the attribute is intended to point out when not using 
the return value is very likely to be wrong. We would expect it to be 
rarely necessary to just suppress the warning.

Best regards
Tim Düsterhus