linux-kernel - [PATCH 4/9] CodingStyle: mention "typedef struct S {} S;" if typedef is used

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Message-ID: <20250509203430.3448-4-adobriyan@gmail.com>
Date: Fri,  9 May 2025 23:34:25 +0300
From: Alexey Dobriyan <adobriyan@...il.com>
To: corbet@....net
Cc: workflows@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: [PATCH 4/9] CodingStyle: mention "typedef struct S {} S;" if typedef is used

Signed-off-by: Alexey Dobriyan <adobriyan@...il.com>
---
 Documentation/process/coding-style.rst | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index ac9c1dbe00b7..5c5902a0f897 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -443,6 +443,20 @@ EVER use a typedef unless you can clearly match one of those rules.
 In general, a pointer, or a struct that has elements that can reasonably
 be directly accessed should **never** be a typedef.
 
+If you must use ``typedef`` consider using identical names for both the type
+and its alias so that the type can be forward declared if necessary:
+
+.. code-block:: c
+
+	typedef struct S { ... } S;
+	typedef union U { ... } U;
+
+	struct S;
+	union U;
+	int f(struct S *s, union U *u);
+
+
+Forward declaring by typedef'ed name doesn't work.
 
 Functions
 ---------
-- 
2.49.0