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Thread-Topic: PHP7 Zend Heap validation
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Date: Sat, 26 Dec 2015 05:01:21 +0000
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Subject: PHP7 Zend Heap validation
From: akin.ocal@thomsonreuters.com

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Hi everyone,

I am working on porting a pre-PHP7 database driver extension to PHP7 for Wi=
ndows platforms.
( I am using PHP 7.0.1 master branch code and targeting non-ZTS 32 bit PHP7=
 on Windows Server 2012 R2 )
And currently as I did mechanical bits of porting ( compilation issues, get=
ting functionality working
mostly followed https://wiki.php.net/phpng-upgrading ) , my extension is on=
ly crash-free if I run it with
USE_ZEND_ALLOC=3D0.

However with USE_ZEND_ALLOC=3D1 , I am getting crashes inside zend_mm_alloc=
_small. As checked with Windbg :
...
if (EXPECTED(heap->free_slot[bin_num] !=3D NULL) )
                {
                                zend_mm_free_slot *p =3D heap->free_slot[bi=
n_num];
                                if ( p->next_free_slot !=3D NULL )

Above , p->next_free_slot is not readable. I believe , currently I am getti=
ng the Zend heap corrupt.
I am running a test script and  I tried disabling many things ,and enabling=
 one by one to have an idea, from the looks of it , I am getting this issue
around a zend_register_resource call but to me that one looks legitimate so=
 I can`t easily pinpoint where the Zend heap gets corrupt.

Diffrently from pre-PHP7 where we had full_mem_check , now I can see ZEND_M=
M_CHECK is placed in memory manager functions.

I wanted to ask if there is any chance if we can have a heap integrity chec=
ker function , or what would you advise
regarding to track down the places in our code corrupting the Zend MM ?

Regards,
Akin Ocal

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