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From:   Max Kellermann <max.kellermann@ionos.com>
To:     linux@roeck-us.net, joe@perches.com,
        Jonathan Corbet <corbet@lwn.net>
Cc:     Max Kellermann <max.kellermann@ionos.com>,
        workflows@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] Documentation/process/coding-style.rst: space around const/volatile
Date:   Tue, 10 Oct 2023 12:12:40 +0200
Message-Id: <20231010101240.992984-1-max.kellermann@ionos.com>
MIME-Version: 1.0
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Precedence: bulk

There are currently no rules on the placement of "const" and
"volatile", but a recent code submission revealed that there is
clearly a preference for spaces around them.

checkpatch.pl has no check at all for this; though it does sometimes
complain, but only because it erroneously thinks that the "*" (on
local variables) is an unary dereference operator, not a pointer type.

Current coding style for const pointers-to-pointers:

 "*const*": 2 occurrences
 "* const*": 3
 "*const *": 182
 "* const *": 681

Just const pointers:

 "*const": 2833 occurrences
 "* const": 16615

Link: https://lore.kernel.org/r/264fa39d-aed6-4a54-a085-107997078f8d@roeck-us.net/
Link: https://lore.kernel.org/r/f511170fe61d7e7214a3a062661cf4103980dad6.camel@perches.com/
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
---
 Documentation/process/coding-style.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 6db37a46d305..b40830517938 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -271,6 +271,18 @@ adjacent to the type name.  Examples:
 	unsigned long long memparse(char *ptr, char **retptr);
 	char *match_strdup(substring_t *s);
 
+Use space around the keywords ``const`` and ``volatile`` (except when
+adjacent to parentheses).  Example:
+
+.. code-block:: c
+
+	const void *a;
+	void * const b;
+	void ** const c;
+	void * const * const d;
+	void * volatile e;
+	int strcmp(const char *a, const char *b);
+
 Use one space around (on each side of) most binary and ternary operators,
 such as any of these::
 
-- 
2.39.2