Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:71252
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.220.176 as permitted sender)
MIME-Version: 1.0
Sender: julienpauli@gmail.com
In-Reply-To: <CAKSD0w7hf-XFaHC+wZpR0yxLp7_rox+dagSukE=SGc1gLFVBVw@mail.gmail.com>
References: <CAH8MpnmBNWC1Kk2cadHyDkNJs_Vq6JXHHiSmG10HRKvAMaR-SA@mail.gmail.com>
 <CAKSD0w725avbxUvPmLbszK5Ynx+QTYbp+UgeoxG0Xwig8mZWpQ@mail.gmail.com> <CAKSD0w7hf-XFaHC+wZpR0yxLp7_rox+dagSukE=SGc1gLFVBVw@mail.gmail.com>
Date: Sat, 18 Jan 2014 21:12:11 +0100
Message-ID: <CAMUwpuRFMH+5LyXjc7oe_qyA11VBErCnxSfC=3OVVjkH50_JOw@mail.gmail.com>
To: Lin Yo-An <cornelius.howl@gmail.com>
Cc: Daniel Lowrey <rdlowrey@php.net>, "internals@lists.php.net" <internals@lists.php.net>
Content-Type: text/plain; charset=Big5
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] Re: How to create Persistent zval?
From: jpauli@php.net (Julien Pauli)

On Sat, Jan 18, 2014 at 9:01 PM, Lin Yo-An <cornelius.howl@gmail.com> wrote=
:
> By the way, Is this the reason of date ext always check the global
> HashTable and re-initialize the tzdata in every request?
>
> Lin Yo-An <cornelius.howl@gmail.com> =A9=F3 2014=A6~1=A4=EB19=A4=E9=ACP=
=B4=C1=A4=E9=BCg=B9D=A1G
>
>>
>>
>> Daniel Lowrey <rdlowrey@php.net <javascript:_e({}, 'cvml',
>> 'rdlowrey@php.net');>> =A9=F3 2014=A6~1=A4=EB19=A4=E9=ACP=B4=C1=A4=E9=BC=
g=B9D=A1G
>>
>>> >> Hello,
>>> >>
>>> >> I am trying to store a zval object into the persistent list in zend =
VM.
>>> >> (Using EG(persistent_list) and zend_rscd_list_entry)
>>> >>
>>> >> Which works fine if I store/fetch the zval in the same request conte=
xt.
>>> >>
>>> >> But it seems that zend engine cleans up the zval object after the
>>> request,
>>> >> when the next request comes, the fetched list entry points to a free=
d
>>> zval
>>> >> address and it makes php segmentationfault. I guess zval is allocate=
d
>>> by
>>> >> emalloc, so I cant keep it cross requests?
>>>
>>> > For persistent alloc, you should use pemalloc() , which is just a
>>> > wrapper leading to libc's malloc.
>>> > If you use emalloc() , the Zend Memory Manager will free the storage
>>> > at the end of the request, thus leading to use-after-free crash if yo=
u
>>> > reuse your pointer on a next request.
>>>
>>> --- Disclaimer ---
>>> I'm passing this along; Joe is having technical difficulties and asked =
for
>>> help sending this to the list. I provide no warranties or refunds ;)
>>> ---
>>>
>>> All zvals passed into the engine must be allocated by the mm, you canno=
t
>>> pemalloc anything and pass it into the engine safely.
>>>
>>> You don't want to store a persistent zval, you want to store a persiste=
nt
>>> resource entry, which should be allocated with pemalloc(size, 1)
>>>
>>> The reason for this is when cleaning up, the engine has no means by whi=
ch
>>> to tell if a zval has been pemalloc or emalloc'd, zval_ptr_dtor works t=
he
>>> same for everything.
>>
>>
>>
>> Thank you so much! That is what i was guessing..  - ref cnt and pemalloc
>> does not work for persistent zval.
>>
>> And zend engine cleans up zvals at the end of request no matter the ref
>> cnt is?
>>
>> so zval is not persistent, then is HashTable persistent?
>>
>> It's because I need to store a zval object which has several properties.
>>  Is there a way to do make the object persistent? Or do i need to serial=
ize
>> it just like apc?

Read the shutdown sequence, and you will figure it out by yourself.
Non-persistent pointers are freed at request shutdown.

http://lxr.php.net/xref/PHP_5_5/Zend/zend_alloc.c#1601

Julien