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Date: Fri, 11 Oct 2019 13:43:09 +0200
Message-ID: <CAH0Uv3F_mP=JPN9RR-bNCu39sMP+UzhCmzYW6p=cqfqiDkvABA@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] exit() via exception
From: andreas@dqxtech.net (Andreas Hennings)

I would think that whichever code currently calls exit() is already
expecting and accepting all the consequences, and assumes that this
won't ever be caught.

So, would it be an option to keep exit() as it is, and introduce a new
syntax construction?

Places where I have seen exit() were not really about exceptional
emergency situations, but rather a "finished" or "done".
E.g. "send headers, print ajax response, exit".
This may or may not be good practice, but it is something being done.

What other use cases exist for exit()?

> introducing *yet another* super-class/interface above Throwable, which is something I'd rather avoid.

I don't see a way to avoid it ..
But if we are going to do this, we should think about whether we
really covered all cases, or if we need another layer in the future.

interface Throwable extends Catchable {}


On Fri, 11 Oct 2019 at 13:05, Nikita Popov <nikita.ppv@gmail.com> wrote:
>
> Hi,
>
> Currently exit() is implemented using bailout and unclean shutdown, which
> means that we're going to perform a longjmp back to the top-level scope and
> let the memory manager clean up all the memory it knows about. Anything not
> allocated using ZMM is going to leak persistently.
>
> For me, one of the most annoying things about this is that we can't perform
> proper leak checks on code using PhpUnit, because it will always exit() at
> the end, which will result in "expected" memory leaks.
>
> I think it would be good to switch exit() to work by throwing a magic
> exception, similar to what Python does. This would allow us to properly
> unwind the stack, executing finally blocks (which are currently skipped)
> and perform a clean engine shutdown.
>
> Depending on the implementation, we could also allow code to actually catch
> this exception, which may be useful for testing scenarios, as well as
> long-running daemons.
>
> I'm mainly wondering how exactly we'd go about integrating this in the
> existing exception hierarchy. Assuming that it is desirable to allow people
> to actually catch this exception, my first thought would be along these
> lines:
>
> Throwable (convert to abstract class)
> \-> Exception
> \-> Error
> \-> ExitThrowable
>
> This does mean though that existing code using catch(Throwable) is going to
> catch exit()s as well. This can be avoided by introducing *yet another*
> super-class/interface above Throwable, which is something I'd rather avoid.
>
> Anyone have thoughts on this matter?
>
> Nikita