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Date: Sun, 9 Nov 2025 18:18:01 +0100
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Subject: Re: [PHP-DEV] [RFC][Discussion] use construct (Block Scoping)
To: Claude Pache <claude.pache@gmail.com>, Edmond Dantes <edmond.ht@gmail.com>
Cc: Seifeddine Gmati <azjezz@carthage.software>, internals@lists.php.net
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

On 11/7/25 20:36, Claude Pache wrote:
> Indeed, and here is a proof (variation on the “Example showing reliable resource management” of the RFC):
> 
> https://3v4l.org/KJaL1
> 
> Something like a `Disposable` interface as suggested in the Future scope section, is probably the only way to make it reliable, and it ought to be part of the RFC.

It is correct that Exceptions will capture parameters, but I don't agree 
with the conclusion that this means that the “future scope” Disposable 
interface is a *necessity*.

Exceptions will only capture the resource if it is passed to an external 
function. In that case, the external function is already capable of 
storing the resource somewhere else for future use. This means that the 
code passing the resource elsewhere must already be prepared that it 
might not close immediately.

In fact the callee might rely on being able to hold onto the resource 
and it remaining valid. It would therefore be invalid for the caller to 
forcibly close it - as I had also mentioned in my (first) reply to Arnaud.

The callee is also able to prevent the capturing of the lock in your 
example, by moving it into a non-parameter local variable. Like this 
(https://3v4l.org/tL5Yt):

     $local_lock = $lock; unset($lock);

I'm not trying to say that this is obvious - I agree that Exceptions 
capturing parameters is something that folks need to learn about - , but 
it is a possible solution to this problem.

Given that I don't agree that Disposable is the solution to the 
“Exception” issue, it's my responsibility to offer an alternative and I 
would like to do this:

The addition of either an attribute or a marker interface for resource 
objects that the backtrace capturing will observe - similarly to the 
#[\SensitiveParameter] attribute. When an object is marked as a resource 
object, then it will be wrapped into a WeakReference when the backtrace 
is captured. As a result, the object will remain accessible for 
backtrace processing / logging as long as it would still be alive if 
there wasn't an Exception. But it will prevent the Exception from 
unexpectedly extending the lifetime in other cases.

In addition I could imagine a WeakReference storing the class name of 
the originally stored object as a “poor man's generic”, allowing folks 
to learn which type of object was originally stored in the weak 
reference, even when the original object is already gone.

Best regards
Tim Düsterhus