Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:124408
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Precedence: bulk
Mime-Version: 1.0 (1.0)
Subject: Re: [PHP-DEV] Breaking change of rounding behavior in PHP 8.4
In-Reply-To: <ba136bd7-7a84-4b88-95cf-2ee336eb1c94@gmx.de>
Cc: PHP Internals <internals@lists.php.net>
Date: Fri, 12 Jul 2024 20:49:06 +0900
Message-ID: <AD9BAD5B-262D-4D78-B903-A2267B722A5A@sakiot.com>
References: <ba136bd7-7a84-4b88-95cf-2ee336eb1c94@gmx.de>
To: "Christoph M. Becker" <cmbecker69@gmx.de>
From: saki@sakiot.com (Saki Takamachi)

Hi Christoph,

> =EF=BB=BFHi all,
>=20
> there has been a "small" change in the rounding logic of
> _php_math_round()[1] a couple of months ago.  A respective ticket,
> claiming the new behavior would be a bug[2] had been filed a while ago
> without proper triage so far.  I'm bringing this to your attention,
> because I'm afraid that there will be (many) more bug reports about this
> in the future (note that the change only affects master, and only PHP
> 8.4.0alpha1 has been released yet, so it is probably not widespreadly
> tested yet).  At the very least we should be sure that we want to keep
> this change, and document it well, to avoid discussions in every filed
> ticket.
>=20
> My personal stance on this is simple: floating point arithmetic is not
> exact per se, and changes to how PHP handles the details should only be
> introduced, if they clearly improve things.  This change apparently
> improves some cases, but worsens others.  Thus, I think the change
> should better be reverted, and if at all, postponed to PHP 9, since I
> neither regard this change as bug fix nor as a feature.
>=20
> What do you think?
>=20
> [1] <https://github.com/php/php-src/pull/12222>
> [2] <https://github.com/php/php-src/issues/14332>
>=20
> Cheers,
> Christoph

As you know, I am the implementer of that change.

At the time, I thought "just add another digit," but this may have been a mo=
re disruptive change than I realized.

I'm not opposed to reverting this, but I don't have any strong opinions on w=
hether it should be reverted.

I'd like to hear other people's opinions as well.

Regards,

Saki=