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From: Greg KH <gregkh@linuxfoundation.org>
To: Matthew Wilcox <willy@infradead.org>, Arnd Bergmann <arnd@arndb.de>
Cc: Roberto Sassu <roberto.sassu@huawei.com>,
	zohar@linux.ibm.com, linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 03/12] digest_lists: Basic definitions
Date: Sun, 27 Jun 2021 17:35:55 +0200	[thread overview]
Message-ID: <YNia23bDCGRZ74OG@kroah.com> (raw)
In-Reply-To: <YNiX7nyQIS/eg+VC@casper.infradead.org>

On Sun, Jun 27, 2021 at 04:23:26PM +0100, Matthew Wilcox wrote:
> On Sun, Jun 27, 2021 at 12:53:47PM +0200, Greg KH wrote:
> > > +enum ops { DIGEST_LIST_ADD, DIGEST_LIST_DEL, DIGEST_LIST_OP__LAST };
> > > +
> > 
> > For enums you export to userspace, you need to specify the values so
> > that all compilers get them right.
> 
> I've never heard that rule before.  Where does it come from?
> https://en.cppreference.com/w/c/language/enum
> says:
> 
>   If enumeration-constant is not followed by = constant-expression,
>   its value is the value one greater than the value of the previous
>   enumerator in the same enumeration. The value of the first enumerator
>   (if it does not use = constant-expression) is zero.
> 

I thought it was in the Documentation/driver-api/ioctl.rst file, but I
can't find it right now.  Maybe it was something that Arnd said?

Arnd, is this still an issue?  For some reason I thought it was always
good to have uapi .h enums be explicit as to the value in them,
otherwise some C compilers might produce other values if they were not
specified?

thanks,

greg k-h

  reply	other threads:[~2021-06-27 15:36 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-25 16:56 [RFC][PATCH 00/12] Huawei Digest Lists Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 01/12] ima: Add digest, algo, measured parameters to ima_measure_critical_data() Roberto Sassu
2021-06-25 18:26   ` Mimi Zohar
2021-06-25 16:56 ` [RFC][PATCH 02/12] digest_lists: Overview Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 03/12] digest_lists: Basic definitions Roberto Sassu
2021-06-27 10:53   ` Greg KH
2021-06-27 15:23     ` Matthew Wilcox
2021-06-27 15:35       ` Greg KH [this message]
2021-06-28  8:30     ` Roberto Sassu
2021-06-28  8:46       ` Greg KH
2021-06-28  9:27         ` Roberto Sassu
2021-06-28  9:32           ` Greg KH
2021-06-28  9:51             ` Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 04/12] digest_lists: Objects Roberto Sassu
2021-06-27 10:56   ` Greg KH
2021-06-28  8:14     ` Roberto Sassu
2021-06-28  8:47       ` Greg KH
2021-06-25 16:56 ` [RFC][PATCH 05/12] digest_lists: Methods Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 06/12] digest_lists: Parser Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 07/12] digest_lists: Interfaces - digest_list_add, digest_list_del Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 08/12] digest_lists: Interfaces - digest_lists_loaded Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 09/12] digest_lists: Interfaces - digest_label Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 10/12] digest_lists: Interfaces - digest_query Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 11/12] digest_lists: Interfaces - digests_count Roberto Sassu
2021-06-25 16:56 ` [RFC][PATCH 12/12] digest_lists: Tests Roberto Sassu

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