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In-Reply-To: <CANUQDCgMgvzUDkguVKVr561jPQiPStH1UYZGcO7ACZK4ikAL+A@mail.gmail.com>
Date: Sat, 10 Feb 2018 23:03:09 +0800
Cc: Aaron Piotrowski <aaron@trowski.com>,
 PHP Internals <internals@lists.php.net>,
 Dmitry Stogov <dmitry@zend.com>
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To: Niklas Keller <me@kelunik.com>
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Subject: Re: [PHP-DEV] [RFC] Fiber support (again)
From: i@lvht.net (=?utf-8?B?5ZCV5rW35rab?=)



> On Feb 10, 2018, at 22:49, Niklas Keller <me@kelunik.com> wrote:
>=20
>> Hi, all,
>>=20
>> I have updated the RFC https://wiki.php.net/rfc/fiber
>>=20
>> changes list:
>>=20
>> - introduce the `throw(Exception $exceptin)` API
>> - record issues discussed
>=20
> What about my suggestion of making PHP's main() automatically a Fiber,
> which avoids Fiber::yield() being used outside of a Fiber, because
> everything is a Fiber?
>=20
> This would require another continuation mechanism, as nothing has
> access to the automatically created main()-Fiber otherwise.
>=20
> There would also need to be something that stops the script execution
> as soon as there's no non-suspended Fiber anymore.

As you pointed out, the main process cannot be a Fiber because it need =
to
schedule other fibers.=20

>=20
> Regarding the internal calls: A core dump / segfault in case of
> Fiber::yield() inside an internal function is unacceptable. It doesn't
> give the user any clue what's wrong. Instead, an exception could be
> thrown from Fiber::yield(), which just bubbles up then. Full support
> for internal functions could be added at a later point then.

It is impossible to solve this issue before we get a pure stackless Zend =
VM.

If this feature can be merged into PHP 7.3, we could introduce a new =
counter
to record the zend vm nested level. Every time you enter an internal =
call,
let zend increment the counter, and decrement it when out.=20

When we create a fiber, we remember current vm nested level. When zend =
execute
Fiber::yield,it will throw an error if the current vm nested level is =
not
equal to the original one.

This feature cannot be implemented without changing the zend vm code =
base.

Maybe we could get a stackless zend vm in the feature. like the =
stackless python

https://github.com/stackless-dev/stackless

>=20
> Regards, Niklas