Re: [PATCH] Makefile: Globally enable fall-through warning

["Gustavo A. R. Silva" <gustavo@embeddedor.com>]

Are you intentionally spamming us?

-Gustavo

On 1/10/26 10:34, MIshraMohit21-LE wrote:
> From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
> 
> Now that all the fall-through warnings have been addressed in the
> kernel, enable the fall-through warning globally.
> 
> Also, update the deprecated.rst file to include implicit fall-through
> as 'deprecated' so people can be pointed to a single location for
> justification.
> 
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: linux-kbuild@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> ---
>   Documentation/process/deprecated.rst | 14 ++++++++++++++
>   Makefile                             |  3 +++
>   2 files changed, 17 insertions(+)
> 
> diff --git a/Documentation/process/deprecated.rst b/Documentation/process/deprecated.rst
> index 49e0f64a3427..053b24a6dd38 100644
> --- a/Documentation/process/deprecated.rst
> +++ b/Documentation/process/deprecated.rst
> @@ -119,3 +119,17 @@ array may exceed the remaining memory in the stack segment. This could
>   lead to a crash, possible overwriting sensitive contents at the end of the
>   stack (when built without `CONFIG_THREAD_INFO_IN_TASK=y`), or overwriting
>   memory adjacent to the stack (when built without `CONFIG_VMAP_STACK=y`)
> +
> +Implicit switch case fall-through
> +---------------------------------
> +The C language allows switch cases to "fall through" when
> +a "break" statement is missing at the end of a case. This,
> +however, introduces ambiguity in the code, as it's not always
> +clear if the missing break is intentional or a bug. As there
> +have been a long list of flaws `due to missing "break" statements
> +<https://cwe.mitre.org/data/definitions/484.html>`_, we no longer allow
> +"implicit fall-through". In order to identify an intentional fall-through
> +case, we have adopted the marking used by static analyzers: a comment
> +saying `/* Fall through */`. Once the C++17 `__attribute__((fallthrough))`
> +is more widely handled by C compilers, static analyzers, and IDEs, we can
> +switch to using that instead.
> diff --git a/Makefile b/Makefile
> index 9be5834073f8..bdf8eac51b07 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -843,6 +843,9 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
>   # warn about C99 declaration after statement
>   KBUILD_CFLAGS += -Wdeclaration-after-statement
>   
> +# Warn about unmarked fall-throughs in switch statement.
> +KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough=3,)
> +
>   # Variable Length Arrays (VLAs) should not be used anywhere in the kernel
>   KBUILD_CFLAGS += -Wvla
>