[PATCH] Documentation/process/coding-style.rst: space around const/volatile

[PATCH] Documentation/process/coding-style.rst: space around const/volatile

[Max Kellermann]

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

Re: [PATCH] Documentation/process/coding-style.rst: space around const/volatile

[Greg KH]

On Tue, Oct 10, 2023 at 12:12:40PM +0200, Max Kellermann wrote:
> 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);

Don't encourage the use of volatile please, it shouldn't be needed in
kernel code (hint, almost all uses of it in the tree is wrong except for
asm statements and some .h files that know they need it for some
hardware operations.)

thanks,

greg k-h

Re: [PATCH] Documentation/process/coding-style.rst: space around const/volatile

[Max Kellermann]

On Tue, Oct 10, 2023 at 1:37 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> Don't encourage the use of volatile please

I don't mean to - but I figured IF "volatile" is used (for whatever
reason, whether correct or not), it should follow the same coding
style as "const".

Do you want me to remove mentions of "volatile" (leaving the coding
style unspecified), or do you want me to add some warning about using
volatile?

Re: [PATCH] Documentation/process/coding-style.rst: space around const/volatile

[Greg KH]

On Tue, Oct 10, 2023 at 02:03:25PM +0200, Max Kellermann wrote:
> On Tue, Oct 10, 2023 at 1:37 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > Don't encourage the use of volatile please
> 
> I don't mean to - but I figured IF "volatile" is used (for whatever
> reason, whether correct or not), it should follow the same coding
> style as "const".
> 
> Do you want me to remove mentions of "volatile" (leaving the coding
> style unspecified), or do you want me to add some warning about using
> volatile?

I would recommend just removing the mentions of it here.

thanks,

greg k-h