linux-kernel - Re: [PATCH v1 2/2] ACPICA: Silence 'unused-but-set variable' warning

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Message-ID: <CAJZ5v0jAy6YmGwZ3QBrgGf4O0xmkF=K=cS71gB0S_0GBC0kLfg@mail.gmail.com>
Date:   Fri, 30 Dec 2022 19:17:51 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Ammar Faizi <ammarfaizi2@...weeb.org>
Cc:     Robert Moore <robert.moore@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Linux ACPI Mailing List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPICA Mailing List <devel@...ica.org>,
        LLVM Mailing List <llvm@...ts.linux.dev>,
        "GNU/Weeb Mailing List" <gwml@...r.gnuweeb.org>
Subject: Re: [PATCH v1 2/2] ACPICA: Silence 'unused-but-set variable' warning

On Fri, Dec 23, 2022 at 3:24 PM Ammar Faizi <ammarfaizi2@...weeb.org> wrote:
>
> From: Ammar Faizi <ammarfaizi2@...weeb.org>
>
> @num_carats is used for debugging, passed to the 'ACPI_DEBUG_PRINT()'
> macro. But this macro will expand to nothing when debug is disabled,
> resulting in the following (clang-16):
>
>   drivers/acpi/acpica/nsaccess.c:295:6: error: variable 'num_carats' set \
>   but not used [-Werror,-Wunused-but-set-variable]
>         u32 num_carats;
>             ^
>   1 error generated.
>
> Move the variable declaration inside the else block to reduce the scope,
> then add '(void)num_carats' to silence the warning when debug is disabled.
>
> Cc: LLVM Mailing List <llvm@...ts.linux.dev>
> Signed-off-by: Ammar Faizi <ammarfaizi2@...weeb.org>

ACPICA changes require (at least) a pull request to be submitted to
the upstream ACPICA project on GitHub.

If such a pull request is created, please resend the Linux patch with
a Link tag pointing to that pull request.

Thanks!

> ---
>  drivers/acpi/acpica/nsaccess.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/acpica/nsaccess.c b/drivers/acpi/acpica/nsaccess.c
> index a0c1a665dfc1..d73d052c5b3b 100644
> --- a/drivers/acpi/acpica/nsaccess.c
> +++ b/drivers/acpi/acpica/nsaccess.c
> @@ -292,7 +292,6 @@ acpi_ns_lookup(union acpi_generic_state *scope_info,
>         struct acpi_namespace_node *current_node = NULL;
>         struct acpi_namespace_node *this_node = NULL;
>         u32 num_segments;
> -       u32 num_carats;
>         acpi_name simple_name;
>         acpi_object_type type_to_check_for;
>         acpi_object_type this_search_type;
> @@ -394,6 +393,7 @@ acpi_ns_lookup(union acpi_generic_state *scope_info,
>                                           "Path is absolute from root [%p]\n",
>                                           this_node));
>                 } else {
> +                       u32 num_carats = 0;
>                         /* Pathname is relative to current scope, start there */
>
>                         ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
> @@ -406,7 +406,6 @@ acpi_ns_lookup(union acpi_generic_state *scope_info,
>                          * the parent node for each prefix instance.
>                          */
>                         this_node = prefix_node;
> -                       num_carats = 0;
>                         while (*path == (u8) AML_PARENT_PREFIX) {
>
>                                 /* Name is fully qualified, no search rules apply */
> @@ -449,6 +448,7 @@ acpi_ns_lookup(union acpi_generic_state *scope_info,
>                                                   "Search scope is [%4.4s], path has %u carat(s)\n",
>                                                   acpi_ut_get_node_name
>                                                   (this_node), num_carats));
> +                               (void)num_carats;
>                         }
>                 }
>
> --
> Ammar Faizi
>