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Date: Sun, 19 Feb 2023 09:45:09 +0100
To: "Max Kellermann" <max+php@blarg.de>
Cc: "Levi Morrison" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] What's the purpose of zend_result?
From: nikita.ppv@gmail.com ("Nikita Popov")

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On Sun, Feb 19, 2023, at 09:21, Max Kellermann wrote:
> On 2023/02/19 08:56, Nikita Popov <nikita.ppv@gmail.com> wrote:
> > If you have a function like zend_stream_open_function(), SUCCESS and FAILURE are directly meaningful values.
> 
> Agree, but that doesn't explain why FAILURE needs to be negative.

I expect that there are two main reasons for that:
 - There are probably some places that return a (non-negative) value or FAILURE.
 - There are probably some places that check for success/failure using >= 0 and < 0. Another POSIX-ism.

I don't think we endorse such usage, but it likely exists.

Let me turn the question around: Is there some reason to change the value of FAILURE at this point?

> > The current guideline for use of bool and zend_result in php-src is that bool is an appropriate return value for "is" or "has" style functions, which return a yes/no answer. zend_result is an appropriate return value for functions that perform some operation that may succeed or fail.
> 
> What does the return value of these functions mean?
> 
> - zend_make_printable_zval()
> - zend_make_callable()
> - zend_parse_arg_bool()
> - zend_fiber_init_context()
> - zend_observer_remove_begin_handler()
> - php_execute_script()1
> 
> If I understand the guideline correctly, then those examples (and
> countless others) are defective and should be fixed, correct?

At least in principle, yes. Of course, actually doing a change may not always be worthwhile, especially as this might result in a silent behavior change for extensions (as putting the return value into an "if" would invert behavior now).

I believe Girgias has done extensive work on making the int vs bool vs zend_result situation more consistent, so you might want to coordinate with him.

Regards,
Nikita
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