Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:92057
Return-Path: <yohgaki@gmail.com>
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Delivered-To: mailing list internals@lists.php.net
Received: (qmail 30412 invoked from network); 1 Apr 2016 01:37:17 -0000
Received: from unknown (HELO lists.php.net) (127.0.0.1)
  by localhost with SMTP; 1 Apr 2016 01:37:17 -0000
Authentication-Results: pb1.pair.com smtp.mail=yohgaki@gmail.com; spf=pass; sender-id=pass
Authentication-Results: pb1.pair.com header.from=yohgaki@gmail.com; sender-id=pass
Received-SPF: pass (pb1.pair.com: domain gmail.com designates 209.85.161.175 as permitted sender)
X-PHP-List-Original-Sender: yohgaki@gmail.com
X-Host-Fingerprint: 209.85.161.175 mail-yw0-f175.google.com  
Received: from [209.85.161.175] ([209.85.161.175:33945] helo=mail-yw0-f175.google.com)
	by pb1.pair.com (ecelerity 2.1.1.9-wez r(12769M)) with ESMTP
	id 04/E7-15473-BC0DDF65 for <internals@lists.php.net>; Thu, 31 Mar 2016 20:37:15 -0500
Received: by mail-yw0-f175.google.com with SMTP id h129so126225671ywb.1
        for <internals@lists.php.net>; Thu, 31 Mar 2016 18:37:15 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=20120113;
        h=mime-version:sender:in-reply-to:references:from:date:message-id
         :subject:to:cc;
        bh=UTr1J7hIwFEmhNY1VW2G2mxzgQg0/PCV5WWik0VzAWo=;
        b=jWUA1jGhSNIYSqKl1btyf0M/ckSeOSf7jSR4beRabYqkVkqvAZYIunfkrzlLxlTHMH
         zXDXebV/sd28A/CUeEYe+pZf3zKdLJwQU0lMIbOtPw7qf1ksDMAFjPoH4tQfvxvDOXu0
         FFuypKl7mdxiMXw7SbatMDaQWNAdkApg3XVlnXtANcyPTR8B8RZIuospOckRC5ZLpqKM
         73b0ZOTuX27a5IBGxDecmfidzMiOIrNsy7dYd3FW/yD3P5NEIXEoulcGMjpqFPDAR5Q1
         1nxM8cYIzPQ22rQX/UOkPubx95eUmsS8GLKf+qNEi5wnvBthpVFGGqhhe5np0vyBy+Hx
         +iww==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=1e100.net; s=20130820;
        h=x-gm-message-state:mime-version:sender:in-reply-to:references:from
         :date:message-id:subject:to:cc;
        bh=UTr1J7hIwFEmhNY1VW2G2mxzgQg0/PCV5WWik0VzAWo=;
        b=Ah0mQEGQiLbNNVnGGolO6sPWDpSKVL2HbxyF3dSlURpZRYVUGMaHXKyYqJOAcojQdt
         eKXdrnHrdTqQC6XTCrnA6WwQRsd3p3K4MR8MJ0h3S7PhBupszw51HmHIYrYdLalzx/Jl
         fyIA3gFJLV9fQ3aEOxRadhP8S5TJKkizm1a5sYQa4IzkL2QgBPy5XUNekg2pIpinuDu5
         LvbyTkbiG1i+XGTVmhpVcZamvMbY1j2uzSgWATzDo4deu9IpaQaPf6O7x9h1v+viehPs
         2szHSDLlWfIqiOa0AEo1QHJgFicETuM0OLyfcs0JLVcHaHbdO0dL54zdOSz5rA7BvYnH
         rmUg==
X-Gm-Message-State: AD7BkJKtg3TqlQEKvM0bIh2g2Jm0j0k780bJ/+mEwFmrMG2ppeULVSjmbDC+udCjvhx7cn0xsV+KSaDJGe8itQ==
X-Received: by 10.31.21.4 with SMTP id 4mr1026105vkv.151.1459474632350; Thu,
 31 Mar 2016 18:37:12 -0700 (PDT)
MIME-Version: 1.0
Sender: yohgaki@gmail.com
Received: by 10.159.40.7 with HTTP; Thu, 31 Mar 2016 18:36:32 -0700 (PDT)
In-Reply-To: <CAGN=FiSPHpnBv2SHLWTQfrZUcOyqkDORn+rpuhDNSr+D+JGpCw@mail.gmail.com>
References: <CAGN=FiSPHpnBv2SHLWTQfrZUcOyqkDORn+rpuhDNSr+D+JGpCw@mail.gmail.com>
Date: Fri, 1 Apr 2016 10:36:32 +0900
X-Google-Sender-Auth: c4G10wMvaw-ZfQMExeQeefHBhYc
Message-ID: <CAGa2bXYgxto2Zt3NkgKq_ZPDUanryj7daCjBknqABVHL+_0eRg@mail.gmail.com>
To: Huqiu Liao <liaohuqiu@gmail.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Copy On Write and Assign By Reference perform different
 on PHP5 and PHP7
From: yohgaki@ohgaki.net (Yasuo Ohgaki)

Hi Huqui,

On Fri, Apr 1, 2016 at 1:47 AM, Huqiu Liao <liaohuqiu@gmail.com> wrote:
> 4    echo (++$i) + (++$i);

I brought up this topic before and the conclusion is
This kind of operation result is undefined and user shouldn't write
such expression.

There are undefined behaviors for ++ and --.

C/C++ has undefined behavior for ++/--
https://en.wikipedia.org/wiki/Undefined_behavior#Examples_in_C_and_C.2B.2B

Some languages do not have these operators for this reason.

PHP may define behavior for these, but it is undefined for future
improvements. (And behavior is changed in PHP 7.0)

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net