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Date: Thu, 25 Dec 2014 13:44:55 +0800
Message-ID: <CABBJUpd=+wUey1xLdC3+D-J9TspC+mARuWbTMDG4zALYA32KCA@mail.gmail.com>
To: Pierre Joye <pierre.php@gmail.com>
Cc: Andrea Faulds <ajf@ajf.me>, Levi Morrison <levim@php.net>, 
	=?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>, 
	PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] About SUCCESS/FAILURE
From: laruence@php.net (Xinchen Hui)

Hey:

On Thu, Dec 25, 2014 at 12:38 PM, Pierre Joye <pierre.php@gmail.com> wrote:
> On Thu, Dec 25, 2014 at 3:06 PM, Andrea Faulds <ajf@ajf.me> wrote:
>>
>>> On 24 Dec 2014, at 23:53, Levi Morrison <levim@php.net> wrote:
>>>
>>> On Wed, Dec 24, 2014 at 4:27 PM, Johannes Schl=C3=BCter
>>> <johannes@schlueters.de> wrote:
>>>> On Wed, 2014-12-24 at 11:13 -0700, Levi Morrison wrote:
>>>>
>>>>> I'm asking for specific things. The reason is that some API's do a
>>>>> non-zero error code; the fact that they are negative is a detail that
>>>>> we should not need to care about.
>>>>
>>>> My guess is that positive values more often might have a meaning ("5
>>>> items changed", "address 0x1234") whereas negative values less often
>>>> have a meaning. Also passing -1 as parameter is more often invalid. Th=
us
>>>> passing -1 is making debug output look more suspicious.
>>>>
>>>>        (while there are  cases where -1 is valid, see recent famous pi=
d
>>>>        =3D fork(); /* ... */ kill(pid, SIGKILL); issue)
>>>
>>> I don't think this is the same use case as SUCCESS and FAILURE. Many
>>> functions have an out parameter which is only valid when the returned
>>> value is SUCCESS. This is not the same thing as an API which returns
>>> an integer and just happen to embed error state in the negative range.
>>> Notably, it doesn't make sense to do `strpos() =3D=3D SUCCESS` to check
>>> success; these are different cases. My question is specifically
>>> directed at the ones that use SUCCESS and FAILURE: which ones require
>>> FAILURE to be negative instead of the normal UNIX-ism of non-zero?
>>>
>>> For the record I am in favor of an enum such as `zend_status` or some
>>> other name which indicates whether an operation succeeded or not for
>>> the reasons already cited in this thread. I just don't see why FAILURE
>>> needs to be negative and want to know why this is the case.
>>
>> Hi Levi,
>>
>> Again, I think the reason FAILURE is -1 is for consistency with other fu=
nctions which use negative return values on error. Some functions return ne=
gative error codes, others just -1. Some functions return useful positive v=
alues, others just 0. But the idea is that all functions return a negative =
number on error, so you can use if (foo() < 0) to check for errors. That=E2=
=80=99s the point of making FAILURE be -1, AIUI. It makes it consistent wit=
h other things, like fork() or strpos().
>
> doing if (foo() < 0  is exactly what should not be done, for any
> function returning a status. Only FAILURE and SUCCESS should be used.
>
> Which value FAILURE and SUCCESS have is not really relevant here but
> to actually be consistent.
>
> For example
>
> ZEND_API int zend_hash_del(HashTable *ht, zend_string *key)
>
> should actually be
>
> ZEND_API status zend_hash_del(HashTable *ht, zend_string *key)
>
> and its usage should be:
>
> if (zend_hash_del(ht, key) =3D=3D FAILURE) {
> ...
> }
>
> Same for zend_parse_parameters and the likes.
>
> However functions like  zval_update_class_constant
> (http://lxr.php.net/xref/PHP_TRUNK/Zend/zend_API.c#1132 ) and all the
> underlying functions, are confusing. Both the signature and the return
> values should rely on FAILURE/SUCCESS.
>
> I think this is what Xinchen means too. Or at least this is what I
> mean with unify the APIs.
yes. and as a soft solution.

we can change these functions which use success/failure return
zend_status instead of int first.

thanks

>
> Cheers,
> --
> Pierre
>
> @pierrejoye | http://www.libgd.org



--=20
Xinchen Hui
@Laruence
http://www.laruence.com/