Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sun, 27 Jun 2021 16:23:26 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Greg KH <gregkh@linuxfoundation.org>
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
Message-ID: <YNiX7nyQIS/eg+VC@casper.infradead.org>
References: <20210625165614.2284243-1-roberto.sassu@huawei.com>
 <20210625165614.2284243-4-roberto.sassu@huawei.com>
 <YNhYu3BXh7f9GkVk@kroah.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YNhYu3BXh7f9GkVk@kroah.com>
Precedence: bulk

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.