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Date: Thu, 21 Jun 2012 11:51:47 +0800
Message-ID: <CABBJUpd3YcZ7kmP1DhMRTc6jvSBLg-NR_5magP-mEzJq4aBYdw@mail.gmail.com>
To: Yader Hernandez <yader.hernandez@gmail.com>
Cc: PHP Developers Mailing List <internals@lists.php.net>
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Subject: Re: [PHP-DEV] destroying an array and using a new one
From: laruence@php.net (Laruence)

On Thu, Jun 21, 2012 at 11:39 AM, Yader Hernandez
<yader.hernandez@gmail.com> wrote:
> I'm trying to reverse an array but I keep getting bizarre results, such a=
s
> seg faults
>
> 0x00000000006d0940 in gc_remove_from_buffer (zv=3D0x7fffffffb550) at
> /home/yaderbh/php-5.4.3/Zend/zend_gc.h:189
> 189 root->next->prev =3D root->prev;
>
> or I'll get "PHP Fatal error: =C2=A0Allowed memory size of" errors when t=
rying
> to manipulate the array in a script.
>
> Basically what I'm doing is creating a pointer to zval, allocating and
> creating the zval into an array, traversing the existing array and
> calling add_index_zval. The position of the index is the current size and
> work my way down.
>
>
> =C2=A0 =C2=A0hash_table =3D Z_ARRVAL_P(intern->elements);
>
>
>
> =C2=A0 =C2=A0ALLOC_INIT_ZVAL(new_elements);
>
> =C2=A0 =C2=A0array_init(new_elements);
>
>
>
> =C2=A0 =C2=A0zend_hash_internal_pointer_reset_ex(hash_table, &pos);
>
>
>
> =C2=A0 =C2=A0i =3D intern->size;
>
>
>
> =C2=A0 =C2=A0while (zend_hash_get_current_data_ex(hash_table, (void **)&c=
urrent,
> &pos) =3D=3D SUCCESS) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0tmp =3D **current;

Hi:
tmp is a stack allocted variable.  when this scope is dead,  *(&tmp)
is undefined value.

you should use a heap allocated variable, or just add_ref the current zval

thanks
>
>
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0zval_copy_ctor(&tmp);
>
>
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0add_index_zval(new_elements, i, &tmp);
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0i--;
>
>
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0zend_hash_move_forward_ex(hash_table, &pos);
>
> =C2=A0 =C2=A0}
>
>
>
> =C2=A0 =C2=A0zval_ptr_dtor(&intern->elements);
>
>
>
> =C2=A0 =C2=A0intern->elements =3D new_elements;
>
>
> Can anyone spot the problem?



--=20
Laruence =C2=A0Xinchen Hui
http://www.laruence.com/