Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   David Laight <David.Laight@ACULAB.COM>
To:     'Zhangjin Wu' <falcon@tinylab.org>, "w@1wt.eu" <w@1wt.eu>
CC:     "arnd@arndb.de" <arnd@arndb.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>,
        "thomas@t-8ch.de" <thomas@t-8ch.de>
Subject: RE: [PATCH v6 06/15] tools/nolibc: __sysret: support syscalls who
 return a pointer
Thread-Topic: [PATCH v6 06/15] tools/nolibc: __sysret: support syscalls who
 return a pointer
Thread-Index: AQHZyGJM8MfmHZ1C3ES1BFx0kL6bna/eeWXw
Date:   Mon, 7 Aug 2023 08:16:02 +0000
Message-ID: <a1732bbffd1542d3b9dd34c92f45076c@AcuMS.aculab.com>
References: <20230806095846.GB10627@1wt.eu>
 <20230806123351.35202-1-falcon@tinylab.org>
In-Reply-To: <20230806123351.35202-1-falcon@tinylab.org>
Accept-Language: en-GB, en-US
MIME-Version: 1.0
Content-Language: en-US
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8BIT
Precedence: bulk

From: Zhangjin Wu
> Sent: 06 August 2023 13:34
...
> Based on your macro version, I tried to use the is_signed_type() from kernel,
> it seems works.

You'll find that (void *)0 isn't 'constant enough' for
is_constexpr() - so is_constexpr((type)0) can be used
to detect pointer types.
Probably requires an 'is_pointer_type()' define.
This also rather means that is_signed_type() needs to be
wrapped in is_constexpr() - probably generating header
file inclusion hell.

I'm going to add a comment on v3 of the patch...

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)