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Date: Mon, 5 Aug 2024 10:42:38 -0600
Message-ID: <CAAKU0ukr=hYb6=M8KE-uPJaNvGOLB8HRj=GegUW9m_EV668rNw@mail.gmail.com>
Subject: Re: [PHP-DEV] Require C11 in PHP 8.4
To: "Gina P. Banyard" <internals@gpb.moe>
Cc: Giovanni Giacobbi <giovanni@giacobbi.net>, Ilija Tovilo <tovilo.ilija@gmail.com>, 
	PHP internals <internals@lists.php.net>
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From: levi.morrison@datadoghq.com (Levi Morrison)

On Sun, Aug 4, 2024 at 10:05=E2=80=AFAM Gina P. Banyard <internals@gpb.moe>=
 wrote:
>
>
> On Friday, 2 August 2024 at 14:33, Giovanni Giacobbi <giovanni@giacobbi.n=
et> wrote:
>
> On Thu, 1 Aug 2024 at 23:57, Ilija Tovilo <tovilo.ilija@gmail.com> wrote:
>>
>> [...]
>> I started fixing these in a PR [1] which required more changes than
>> expected. After a short discourse, we were wondering whether it might
>> be better to switch to a newer C standard instead. Our coding
>> standards [2] currently specify that compiling php-src requires C99.
>> The Unix installation page on php.net [3] claims it is ANSI C, which
>> is certainly outdated. There have been suggestions to require C11 for
>> a while, which should be well supported by all compilers shipped with
>> maintained distributions.
>
>
> It feels wrong to raise such an important requirement that might affect a=
 lot of people, including maintainers of extensions, for just one specific =
problem, and 99% of the codebase would still be C99 compliant.
>
> I quickly put together an alternative PR (#15202) with a slightly differe=
nt approach, just as a proof of concept. The idea is to move all the global=
 typedefs in a new include header "zend_types_defs.h" (but also zend_portab=
ility.h can be reused for this purpose, as all the relevant files already i=
nclude it).
>
> While putting together that PR, I had the feeling that this typedef redef=
inition problem is in reality hiding some smelly design of header files. So=
 maybe, rather than requiring a compiler more tolerant to poor code, we sho=
uld rather focus on getting the design right.
>
>
> I would like to see actual factual data rather than "vibes" as to how thi=
s would cause issues with third-party extensions.
> php-src is not C99 pedeantic compliant and we do use GCC extenstions.
>
> I do agree that maybe we should go back to fixing headers, but considerin=
g the drama this caused 18 months ago I do not know who here has the motiva=
tion to do this.
>
> Ideally I feel we should target C17 as it is a "bug fix" release of C11, =
but this might be impossible due to old compilers still being the default o=
n LTS Distributions.
> The main benefit of C11/17 in the long run are atomics, that we kinda use=
 already anyway.

As a person who wrote some of those atomics, I would definitely prefer
to move to standard C11/C17 atomics at some point in the future and
remove all other fallbacks. The blocker right now is Microsoft Visual
Studio. Although they added C11/C17 support a few versions back, they
did not add atomics at that time. It's available now, but it is still
experimental as far as I can tell.

Maybe for PHP 9.0 we can address header issues and also by then VS
will have a general release we can move to for atomics.

One thing I feel strongly about is that we should not add flags like
`-std=3Dc11`. If we check, we ought to just ensure that whatever flags
the user provided, we have certain C11/C17 features. This allows for
extensions to use a newer version, or a relaxed version like
`-std=3Dgnu11`.