Re: [PATCH] LoongArch: Fix use of logical '&&' with constant operand

[Huacai Chen]

On Tue, Mar 4, 2025 at 6:53 PM WangYuli <wangyuli@xxxxxxxxxxxxx> wrote:
>
> Fix follow error with clang-19:
>
> arch/loongarch/kernel/setup.c:335:40: error: use of logical '&&' with constant operand [-Werror,-Wconstant-logical-operand]
>   335 |         if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
>       |                                               ^  ~~~~~~~~~~~~~~~~~
> arch/loongarch/kernel/setup.c:335:40: note: use '&' for a bitwise operation
>   335 |         if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
>       |                                               ^~
>       |                                               &
> arch/loongarch/kernel/setup.c:335:40: note: remove constant to silence this warning
>   335 |         if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
>       |                                               ^~~~~~~~~~~~~~~~~~~~
> 1 error generated.
Are you kidding me? CONFIG_CMDLINE[0] is a constant for a specific
config but the config is variable across buildings. So the "constant"
for compilers is not as "constant" for people. Compiler warnings
should be double-checked by people, right?

Huacai

>
> Fixes: 83da30d73b86 ("LoongArch: Fix CMDLINE_EXTEND and CMDLINE_BOOTLOADER handling")
> Co-developed-by: Wentao Guan <guanwentao@xxxxxxxxxxxxx>
> Signed-off-by: Wentao Guan <guanwentao@xxxxxxxxxxxxx>
> Signed-off-by: Yuli Wang <wangyuli@xxxxxxxxxxxxx>
> ---
>  arch/loongarch/kernel/setup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/kernel/setup.c b/arch/loongarch/kernel/setup.c
> index edcfdfcad7d2..834bea7f42da 100644
> --- a/arch/loongarch/kernel/setup.c
> +++ b/arch/loongarch/kernel/setup.c
> @@ -332,7 +332,7 @@ static void __init bootcmdline_init(char **cmdline_p)
>          * Append built-in command line to the bootloader command line if
>          * CONFIG_CMDLINE_EXTEND is enabled.
>          */
> -       if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && CONFIG_CMDLINE[0]) {
> +       if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) && !!CONFIG_CMDLINE[0]) {
>                 strlcat(boot_command_line, " ", COMMAND_LINE_SIZE);
>                 strlcat(boot_command_line, CONFIG_CMDLINE, COMMAND_LINE_SIZE);
>         }
> --
> 2.47.2
>