linux-kernel - Re: [PATCH v4 2/2] ARM: ftrace: Add MODULE

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Date:   Tue, 13 Mar 2018 19:24:59 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v4 2/2] ARM: ftrace: Add MODULE_PLTS support

Hi!

On 13/03/18 18:51, Ard Biesheuvel wrote:
>>> if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS))
>>>     module_plt_alloc_fixed();
>> Do you consider this a legal C code if without module-plts.o the function would not exist at all?
>> That's too much relying on optimizer I think...
>>
> Yes, we rely on that in many different places in the kernel.

https://www.kernel.org/doc/Documentation/process/coding-style.rst:
"However, this approach still allows the C compiler to see the code
inside the block, and check it for correctness (syntax, types, symbol
references, etc).  Thus, you still have to use an #ifdef if the code inside the
block references symbols that will not exist if the condition is not met."

But we can of course ignore it.

-- 
Best regards,
Alexander Sverdlin.