Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:89153
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain zend.com designates 209.85.213.181 as permitted sender)
MIME-Version: 1.0
In-Reply-To: <CA+9eiLsgDUUXgrtTbTF3XKreZCeC9knch=AjSxSedB5EKjaf=g@mail.gmail.com>
References: <CA+9eiLvDmAMeYuiEvD=huG7Pt_2k59804oz3Wez0FyB7BJYYVQ@mail.gmail.com>
	<CAF+90c9bJMq3B=j=rcoLNmFD4L7JhwuP-FQ+0HihcG0PhwHYBA@mail.gmail.com>
	<CA+9eiLsgDUUXgrtTbTF3XKreZCeC9knch=AjSxSedB5EKjaf=g@mail.gmail.com>
Date: Tue, 10 Nov 2015 22:28:30 +0300
Message-ID: <CA+9eiLviHP=jB+bUHvQemgHnaNdZeqP=Pg_QoLbtgtoX0D9q0g@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Xinchen Hui <xinchen.h@zend.com>, Bob Weinand <bobwei9@hotmail.com>, 
	PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=047d7b3a9c76f83517052434b6c3
Subject: Re: Safe Temporary Cleanup on Exception (Variable Liveness)
From: dmitry@zend.com (Dmitry Stogov)

--047d7b3a9c76f83517052434b6c3
Content-Type: text/plain; charset=UTF-8

I've committed unrelated and obvious parts (without semantic changes).
The updated and extended patch now is much more clean
https://gist.github.com/dstogov/43eaa3f3b68583877322
Anyway, it's still incomplete.

Thanks. Dmitry.

On Tue, Nov 10, 2015 at 2:29 PM, Dmitry Stogov <dmitry@zend.com> wrote:

>
>
> On Tue, Nov 10, 2015 at 1:42 PM, Nikita Popov <nikita.ppv@gmail.com>
> wrote:
>
>> On Tue, Nov 10, 2015 at 10:53 AM, Dmitry Stogov <dmitry@zend.com> wrote:
>>
>>> Hi,
>>>
>>> Please take a look into
>>> https://gist.github.com/dstogov/43eaa3f3b68583877322
>>>
>>> This is variation on Bob's idea about variable liveness.
>>> The patch is incomplete. Liveness construction is still naive. However,
>>> all tests are passed.
>>>
>>> Ranges are represented by start/end/variable cartages. (I suppose this
>>> representation is more compact, than in the original proposal).
>>> In general, it's possible to use few ranges for the same variable, if
>>> its whole live range is not linear. (this is not implemented yet).
>>>
>>> Related ideas and tests are welcome.
>>>
>>> Thanks. Dmitry.
>>>
>>
>> One leak this does not cover yet is a discarded delayed return value:
>>
>> function test() {
>>     try {
>>         $a = [1, 2, 3];
>>         return $a + [];
>>     } finally {
>>         throw new Exception;
>>     }
>> }
>>
>> try {
>>     test();
>> } catch (Exception $e) {}
>>
>> This case is a bit tricky because it violates the usual invariant that
>> all temporaries have well-defined liveness ranges (either alive or not, no
>> maybe). We'd have to change that first.
>>
>
> I see the problem. We can't statically define live-ranges for finally
> code, because we don't know where it's going to be called from.
> May be we may reconstruct this at run-time.
>
> Thanks. Dmitry,
>
>
>
>>
>> Nikita
>>
>>
>

--047d7b3a9c76f83517052434b6c3--