linux-kernel - Re: [PATCH] of: declare string literals const

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Message-ID: <90998e63-056e-52e6-03d2-775fc65d901d@gmail.com>
Date:   Fri, 14 Oct 2022 13:42:48 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Christian Göttsche <cgzones@...glemail.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH] of: declare string literals const

On 10/12/22 12:46, Christian Göttsche wrote:
> of_overlay_action_name() returns a string literal from a function local
> array.  Modifying string literals is undefined behavior which usage of
> const pointer can avoid.  of_overlay_action_name() is currently only
> used once in overlay_notify() to print the returned value.
> 
> While on it declare the data array const as well.
> 
> Reported by Clang:
> 
>     In file included from arch/x86/kernel/asm-offsets.c:22:
>     In file included from arch/x86/kernel/../kvm/vmx/vmx.h:5:
>     In file included from ./include/linux/kvm_host.h:19:
>     In file included from ./include/linux/msi.h:23:
>     In file included from ./arch/x86/include/asm/msi.h:5:
>     In file included from ./arch/x86/include/asm/irqdomain.h:5:
>     In file included from ./include/linux/irqdomain.h:35:
>     ./include/linux/of.h:1555:3: error: initializing 'char *' with an expression of type 'const char[5]' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>                     "init",
>                     ^~~~~~
>     ./include/linux/of.h:1556:3: error: initializing 'char *' with an expression of type 'const char[10]' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>                     "pre-apply",
>                     ^~~~~~~~~~~
>     ./include/linux/of.h:1557:3: error: initializing 'char *' with an expression of type 'const char[11]' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>                     "post-apply",
>                     ^~~~~~~~~~~~
>     ./include/linux/of.h:1558:3: error: initializing 'char *' with an expression of type 'const char[11]' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>                     "pre-remove",
>                     ^~~~~~~~~~~~
>     ./include/linux/of.h:1559:3: error: initializing 'char *' with an expression of type 'const char[12]' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
>                     "post-remove",
>                     ^~~~~~~~~~~~~
> 
> Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> ---
>  include/linux/of.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 6b79ef9a6541..8b9f94386dc3 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -1549,9 +1549,9 @@ enum of_overlay_notify_action {
>  	OF_OVERLAY_POST_REMOVE,
>  };
>  
> -static inline char *of_overlay_action_name(enum of_overlay_notify_action action)
> +static inline const char *of_overlay_action_name(enum of_overlay_notify_action action)
>  {
> -	static char *of_overlay_action_name[] = {
> +	static const char *const of_overlay_action_name[] = {
>  		"init",
>  		"pre-apply",
>  		"post-apply",

Reviewed-by: Frank Rowand <frowand.list@...il.com>