Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:18392
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Message-ID: <6.2.3.4.2.20050824163046.05e01330@localhost>
Date: Wed, 24 Aug 2005 16:31:08 -0700
To: Rasmus Lerdorf <rasmus@lerdorf.com>,internals <internals@lists.php.net>
Cc: Stanislav Malyshev <stas@zend.com>
In-Reply-To: <430CEA87.7040805@lerdorf.com>
References: <430CEA87.7040805@lerdorf.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed
Subject: Re: [PHP-DEV] Schroedinger Objects
From: andi@zend.com (Andi Gutmans)

Yep I think that's a good point.
Checking for cast is the right thing IMO.

At 02:45 PM 8/24/2005, Rasmus Lerdorf wrote:
>As per bug #34199 and as Rob points out, if($obj) and if(!$obj) are
>handled by different opcodes and these two opcodes are inconsistent in
>whether they call an object's cast_object handler.
>
>if($obj) results in a ZEND_JMPZ_SPEC_CV_HANDLER which calls
>i_zend_is_true() which always return true for objects, no matter what
>(ignore compatibility mode here) because of this code in zend_execute.h:
>
>         case IS_OBJECT:
>             if(IS_ZEND_STD_OBJECT(*op)) {
>                 TSRMLS_FETCH();
>                 if(EG(ze1_compatibility_mode)) {
>                     result = (zend_hash_num_elements(Z_OBJPROP_P(op))?1:0);
>                 } else {
>                     result = 1;
>                 }
>             } else {
>                 result = 1;
>             }
>             break;
>
>if(!$obj) results in a which calls convert_to_boolean() which in turn
>calls convert_object_to_type() which has:
>
>if (Z_OBJ_HT_P(op)->cast_object) {
>
>     if (Z_OBJ_HT_P(op)->cast_object(op, op, ctype, 1 TSRMLS_CC) ==
>SUCCESS) {
>          op->type = ctype;
>
>     }
>
>This means that any object which actually implements a cast_object
>handler that returns false under some condition will be broken.  The
>simple example is:
>
>   $a = simplexml_load_string('<a></a>');
>   if($a && !$a) echo "BUG!";
>
>I think we need to fix i_zend_is_true's IS_OBJECT case to check to see
>if the object has a cast_object handler and call it or just call
>convert_to_boolean() there.  Or we need to clean this up and not have
>such different codepaths for these two cases.
>
>-Rasmus
>
>--
>PHP Internals - PHP Runtime Development Mailing List
>To unsubscribe, visit: http://www.php.net/unsub.php