On 9/30/21 12:24 PM, Kees Cook wrote:
While discussing how to format the addition of various function
attributes, some "unwritten rules" of ordering surfaced[1]. Capture as
close as possible to Linus's preferences for future reference.
(Though I note the dissent voiced by Joe Perches, Alexey Dobriyan, and
others that would prefer all attributes live on a separate leading line.)
[1] https://lore.kernel.org/mm-commits/CAHk-=wiOCLRny5aifWNhr621kYrJwhfURsa0vFPeUEm8mF0ufg@xxxxxxxxxxxxxx/
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
Documentation/process/coding-style.rst | 30 ++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/Documentation/process/coding-style.rst b/Documentation/process/coding-style.rst
index 42969ab37b34..6b4feb1c71e7 100644
--- a/Documentation/process/coding-style.rst
+++ b/Documentation/process/coding-style.rst
@@ -487,6 +487,36 @@ because it is a simple way to add valuable information for the reader.
Do not use the ``extern`` keyword with function prototypes as this makes
lines longer and isn't strictly necessary.
+When writing a function declarations, please keep the `order of elements regular
+<https://lore.kernel.org/mm-commits/CAHk-=wiOCLRny5aifWNhr621kYrJwhfURsa0vFPeUEm8mF0ufg@xxxxxxxxxxxxxx/>`_.
+For example::
+
+ extern __init void * __must_check void action(enum magic value, size_t size,
Drop that second "void" ? or what does it mean?
Can __must_check and void be used together?
+ u8 count, char *fmt, ...) __printf(4, 5) __malloc;
+
+The preferred order of elements for a function prototype is:
+
+- storage class (here, ``extern``, and things like ``static __always_inline`` even though
+ ``__always_inline`` is technically an attribute, it is treated like ``inline``)
+- storage class attributes (here, ``__init`` -- i.e. section declarations, but also things like ``__cold``)
+- return type (here, ``void *``)
+- return type attributes (here, ``__must_check``)
I'm not trying to get you to change this, but I would prefer to see
extern __init __must_check void *action(...) <attributes>;
i.e., with the return type adjacent to the function name.
+- function name (here, ``action``)
+- function parameters (here, ``(enum magic value, size_t size, u8 count, char *fmt, ...)``, noting that parameter names should always be included)
+- function parameter attributes (here, ``__printf(4, 5)``)
+- function behavior attributes (here, ``__malloc``)
+
+Note that for a function definition (e.g. ``static inline``), the compiler does
+not allow function parameter attributes after the function parameters. In these
+cases, they should go after the storage class attributes (e.g. note the changed
+position of ``__printf(4, 5)``)::
+
+ static __always_inline __init __printf(4, 5) void * __must_check void action(
+ enum magic value, size_t size, u8 count, char *fmt, ...)
+ __malloc
+ {
+ ...
+ }
7) Centralized exiting of functions
-----------------------------------
thanks.
--
~Randy
