On 7/1/22 15:20, Martin Fernandez wrote:
> Add a description to the MACRO_ARG_REUSE check.
>
> I feel like this is also a good place to put a workaround although I'm
> not sure if there is a cannonical way to solve those kinds of issues.
canonical
The usual way in the kernel is to declare a local _x and local _y (for your
example below). See how it is done in include/linux/minmax.h for min_not_zero().
>
> Signed-off-by: Martin Fernandez <martin.fernandez@xxxxxxxxxxxxx>
> ---
> Documentation/dev-tools/checkpatch.rst | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/Documentation/dev-tools/checkpatch.rst b/Documentation/dev-tools/checkpatch.rst
> index b52452bc2963..43fa99f188f5 100644
> --- a/Documentation/dev-tools/checkpatch.rst
> +++ b/Documentation/dev-tools/checkpatch.rst
> @@ -759,6 +759,21 @@ Indentation and Line Breaks
> Macros, Attributes and Symbols
> ------------------------------
>
> + **ARG_REUSE**
> + Using the same argument multiple times in the macro definition
> + would lead to unwanted side-effects.
> +
> + For example, given a `min` macro defined like::
> +
> + #define min(x, y) ((x) < (y) ? (x) : (y))
> +
> + If you call it with `min(foo(x), 0)` would expand to::
> +
> + foo(x) < 0 ? foo(x) : 0
> +
> + If `foo` have side-effects or it's an expensive calculation the
> + results might not be what the user inteded.
intended.
> +
> **ARRAY_SIZE**
> The ARRAY_SIZE(foo) macro should be preferred over
> sizeof(foo)/sizeof(foo[0]) for finding number of elements in an
thanks.
--
~Randy
