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Date: Thu, 25 Dec 2014 15:38:05 +1100
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To: Andrea Faulds <ajf@ajf.me>
Cc: Levi Morrison <levim@php.net>, =?UTF-8?Q?Johannes_Schl=C3=BCter?= <johannes@schlueters.de>, 
	PHP internals <internals@lists.php.net>, Laruence <laruence@php.net>
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Subject: Re: [PHP-DEV] About SUCCESS/FAILURE
From: pierre.php@gmail.com (Pierre Joye)

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. Thu=
s
>>> passing -1 is making debug output look more suspicious.
>>>
>>>        (while there are  cases where -1 is valid, see recent famous pid
>>>        =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 fun=
ctions which use negative return values on error. Some functions return neg=
ative error codes, others just -1. Some functions return useful positive va=
lues, others just 0. But the idea is that all functions return a negative n=
umber 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.

Cheers,
--=20
Pierre

@pierrejoye | http://www.libgd.org