linux-kernel - Re: [PATCH] kconfig: Warn if choice default is not in choice

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Message-ID: <CAFkk2KSJh6OK+s7oQFVu-QEZn0K_wfXjUNFJqxuCy2H6VXi0wQ@mail.gmail.com>
Date:   Thu, 5 Oct 2017 05:12:15 +0200
From:   Ulf Magnusson <ulfalizer@...il.com>
To:     yann.morin.1998@...e.fr, linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Ulf Magnusson <ulfalizer@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Arnaud Lacombe <lacombar@...il.com>
Subject: Re: [PATCH] kconfig: Warn if choice default is not in choice

On Wed, Oct 4, 2017 at 2:10 AM, Ulf Magnusson <ulfalizer@...il.com> wrote:
> On Wed, Oct 4, 2017 at 1:25 AM, Ulf Magnusson <ulfalizer@...il.com> wrote:
>> This will catch mistakes like in the following real-world example, where
>> a "CONFIG_" prefix snuck in, making an undefined symbol the default:
>>
>>         choice
>>                 prompt "Compiler optimization level"
>>                 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
>>
>>         config CC_OPTIMIZE_FOR_PERFORMANCE
>>                 ...
>>
>>         config CC_OPTIMIZE_FOR_SIZE
>>                 ...
>>
>>         endchoice
>>
>> This now prints the following warning:
>>
>>         init/Kconfig:1036:warning: choice default symbol 'CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE' is not contained in the choice
>>
>> Cases where the default symbol belongs to the wrong choice are also
>> detected.
>>
>> (The mistake is harmless here: Since the default symbol is not visible,
>> the choice falls back on using the first visible symbol as the default,
>> which is CC_OPTIMIZE_FOR_PERFORMANCE, as intended.)
>>
>> Discovered while playing around with Kconfiglib
>> (https://github.com/ulfalizer/Kconfiglib).
>>
>> Signed-off-by: Ulf Magnusson <ulfalizer@...il.com>
>> ---
>>  scripts/kconfig/menu.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
>> index e935793..ce88de8 100644
>> --- a/scripts/kconfig/menu.c
>> +++ b/scripts/kconfig/menu.c
>> @@ -252,6 +252,16 @@ static void sym_check_prop(struct symbol *sym)
>>                                             "'%s': number is invalid",
>>                                             sym->name);
>>                         }
>> +                       if (sym_is_choice(sym)) {
>> +                               struct property *choice_prop =
>> +                                       sym_get_choice_prop(sym2);
>> +
>> +                               if (!choice_prop ||
>> +                                   prop_get_symbol(choice_prop) != sym)
>> +                                       prop_warn(prop,
>> +                                                 "choice default symbol '%s' is not contained in the choice",
>> +                                                 sym2->name);
>> +                       }
>>                         break;
>>                 case P_SELECT:
>>                 case P_IMPLY:
>> --
>> 2.7.4
>>
>
> A patch to fix the compiler optimization level choice has been
> submitted as well:
> https://lkml.org/lkml/2017/10/3/991
>
> Cheers,
> Ulf

Adding some CCs just because I forgot. No panic.

Cheers,
Ulf