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zend_call_method with arguments passed by reference

php.internals

Unnamed Person

6 years ago

Hello,

I hope this is the appropriate mailing list, please redirect me to better
please if required.

I am currently rewriting our PHP extension from PHP5 to PHP7.

To call PHP methods from our C/C++ code we use slightly modified
zend_call_method from Zend/zend_interfaces.c (to use more arguments than 2).

Now I found out that it does not work with arguments passed by reference,
such as:

public function FuncWithRef(array &$changeThis)

if values are changed in the PHP code then zval values back in C part after
zend_call_function call are not influenced.

With PHP5 the value was overwritten and could be used later in C code.

Previously the zend_fcall_info struct for function call was filled with
params simply by

params[0] = &arg1;

In PHP7 this is changed to

ZVAL_COPY_VALUE(&params[0], arg1);

After function is executed (zend_call_function) both fci.params and arg1
contain still the original zval values,

changes made in PHP code are not available. Is there any way how to solve
this?

I am mainly searching for and comparing code snippets in PHP/ext folder to
see how things were rewritten from PHP5 to PHP7.

Sorry if I missed something obvious and thank you for your help.

Nikita Popov

6 years ago

On Wed, Jan 8, 2020 at 3:59 PM mdolezal.noctuint.cz via internals <
internals@lists.php.net> wrote:

> Hello,
>
> I hope this is the appropriate mailing list, please redirect me to better
> please if required.
>
>
>
> I am currently rewriting our PHP extension from PHP5 to PHP7.
>
> To call PHP methods from our C/C++ code we use slightly modified
> zend_call_method from Zend/zend_interfaces.c (to use more arguments than
> 2).
>
>
> Now I found out that it does not work with arguments passed by reference,
> such as:
>
> public function FuncWithRef(array &$changeThis)
>
>
>
> if values are changed in the PHP code then zval values back in C part after
> zend_call_function call are not influenced.
>
> With PHP5 the value was overwritten and could be used later in C code.
>
> Previously the zend_fcall_info struct for function call was filled with
> params simply by
>
>
>
> params[0] = &arg1;
>
>
>
> In PHP7 this is changed to
>
>
>
> ZVAL_COPY_VALUE(&params[0], arg1);
>
>
>
> After function is executed (zend_call_function) both fci.params and arg1
> contain still the original zval values,
>
> changes made in PHP code are not available. Is there any way how to solve
> this?
>
> I am mainly searching for and comparing code snippets in PHP/ext folder to
> see how things were rewritten from PHP5 to PHP7.
>
> Sorry if I missed something obvious and thank you for your help.
>

It looks like the implementation of zend_call_method() does not support
this, as it does not copy parameters back after the call. I'd suggest to
use the lower level zend_call_function() for the cases where you need this
for now.

Nikita

Unnamed Person

6 years ago

Thank you for your answer Nikita.
Can you please give me more details what you mean? I can try that approach.
zend_call_method copies the args to params array which is assigned to zend_fcall_info fci.
I can pass there for example "test" zval string.
Then the mentioned lower level zend_call_function() is called with fci as parameter, that's what I do.
In PHP code "test" is changed to "changed".
But after the call the fci.params are not changed, still "test", so I have nothing to copy back manually.


-----Original Message-----
From: Nikita Popov <nikita.ppv@gmail.com>
Sent: Wednesday, January 8, 2020 4:06 PM
To: mdolezal@noctuint.cz
Cc: PHP internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] zend_call_method with arguments passed by reference

On Wed, Jan 8, 2020 at 3:59 PM mdolezal.noctuint.cz via internals < internals@lists.php.net> wrote:

> Hello,
>
> I hope this is the appropriate mailing list, please redirect me to
> better please if required.
>
>
>
> I am currently rewriting our PHP extension from PHP5 to PHP7.
>
> To call PHP methods from our C/C++ code we use slightly modified
> zend_call_method from Zend/zend_interfaces.c (to use more arguments
> than 2).
>
>
> Now I found out that it does not work with arguments passed by
> reference, such as:
>
> public function FuncWithRef(array &$changeThis)
>
>
>
> if values are changed in the PHP code then zval values back in C part
> after zend_call_function call are not influenced.
>
> With PHP5 the value was overwritten and could be used later in C code.
>
> Previously the zend_fcall_info struct for function call was filled
> with params simply by
>
>
>
> params[0] = &arg1;
>
>
>
> In PHP7 this is changed to
>
>
>
> ZVAL_COPY_VALUE(&params[0], arg1);
>
>
>
> After function is executed (zend_call_function) both fci.params and
> arg1 contain still the original zval values,
>
> changes made in PHP code are not available. Is there any way how to
> solve this?
>
> I am mainly searching for and comparing code snippets in PHP/ext
> folder to see how things were rewritten from PHP5 to PHP7.
>
> Sorry if I missed something obvious and thank you for your help.
>

It looks like the implementation of zend_call_method() does not support this, as it does not copy parameters back after the call. I'd suggest to use the lower level zend_call_function() for the cases where you need this for now.

Nikita

Nikita Popov

6 years ago

On Wed, Jan 8, 2020 at 4:18 PM <mdolezal@noctuint.cz> wrote:

> Thank you for your answer Nikita.
> Can you please give me more details what you mean? I can try that approach.
> zend_call_method copies the args to params array which is assigned to
> zend_fcall_info fci.
> I can pass there for example "test" zval string.
> Then the mentioned lower level zend_call_function() is called with fci as
> parameter, that's what I do.
> In PHP code "test" is changed to "changed".
> But after the call the fci.params are not changed, still "test", so I have
> nothing to copy back manually.
>

fci.params *should* contain the changed parameters after the call, at least
assuming no_separation=0. It's not clear to me under what circumstances
that wouldn't work.

Nikita

Unnamed Person

6 years ago

Thanks a lot Nikita,
that’s it. I was not aware of no_separation influence, it was set to 1 in zend_call_method both in PHP5 and PHP7 so I didn't touch it during migration. I need to copy the arguments properly back now but basically it's working. Thanks again,
Martin

-----Original Message-----
From: Nikita Popov <nikita.ppv@gmail.com>
Sent: Thursday, January 9, 2020 1:17 PM
To: mdolezal@noctuint.cz
Cc: PHP internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] zend_call_method with arguments passed by reference

On Wed, Jan 8, 2020 at 4:18 PM <mdolezal@noctuint.cz> wrote:

> Thank you for your answer Nikita.
> Can you please give me more details what you mean? I can try that approach.
> zend_call_method copies the args to params array which is assigned to
> zend_fcall_info fci.
> I can pass there for example "test" zval string.
> Then the mentioned lower level zend_call_function() is called with fci
> as parameter, that's what I do.
> In PHP code "test" is changed to "changed".
> But after the call the fci.params are not changed, still "test", so I
> have nothing to copy back manually.
>

fci.params *should* contain the changed parameters after the call, at least assuming no_separation=0. It's not clear to me under what circumstances that wouldn't work.

Nikita