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From:   Ard Biesheuvel <ard.biesheuvel@linaro.org>
Date:   Fri, 9 Mar 2018 08:19:50 +0000
Message-ID: <CAKv+Gu-AuY=qPddZeKpidMY6thnP4z4R=bN7M63kDL32NQUMBA@mail.gmail.com>
Subject: Re: [PATCH 12/12] efi: make const array 'apple' static
To:     Ingo Molnar <mingo@kernel.org>
Cc:     linux-efi@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Colin Ian King <colin.king@canonical.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On 9 March 2018 at 08:07, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> On 9 March 2018 at 08:04, Ingo Molnar <mingo@kernel.org> wrote:
>>
>> * Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
>>
>>> > Also, would it make sense to rename it to something more descriptive like
>>> > "apple_unicode_str[]" or so?
>>> >
>>> > Plus an unicode string literal initializer would be pretty descriptive as well,
>>> > instead of the weird looking character array, i.e. something like:
>>> >
>>> >   static efi_char16_t const apple_unicode_str[] = u"Apple";
>>> >
>>> > ... or so?
>>> >
>>>
>>> is u"xxx" the same as L"xxx"?
>>
>> So "L" literals map to wchar_t, which wide character type is implementation
>> specific IIRC, could be 16-bit or 32-bit wide.
>>
>> u"" literals OTOH are specified by the C11 spec to be char16_t, i.e. 16-bit wide
>> characters - which I assume is the EFI type as well?
>>
>>> In any case, this is for historical reasons: at some point (and I
>>> don't remember the exact details) we had a conflict at link time with
>>> objects using 4 byte wchar_t, so we started using this notation to be
>>> independent of the size of wchar_t. That issue no longer exists so we
>>> should be able to get rid of this.
>>
>> Yes, my guess is that those problems were due to L"xyz" mapping to wchar_t and
>> having a different type in the kernel build and the host build side - but u"xyz"
>> should solve that.
>>
>
> Excellent!
>
> Do you mind taking this patch as is? I will follow up with a patch
> that updates all occurrences of this pattern (we have a few of them),
> i.e., use u"" notation and move them to file scope.

OK, I misremembered: the other occurrences have already been moved to
file scope a while ago.

I will follow up with a patch that switches to u"" notation, please
let me know if I should respin this or not