Date: Mon, 5 Jun 2017 12:00:26 -0500 From: Pedro Giffuni <pfg@FreeBSD.org> To: Eric van Gyzen <vangyzen@FreeBSD.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Function attribute for optimization level Message-ID: <0e9c89aa-920f-26bb-abde-2f4901740933@FreeBSD.org> In-Reply-To: <ec177111-2dae-f1c3-034f-df9f65c30da2@FreeBSD.org> References: <ec177111-2dae-f1c3-034f-df9f65c30da2@FreeBSD.org>
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On 04/06/2017 23:08, Pedro Giffuni wrote:
>
> Hi Eric;
>
> It is a good idea : the nonopt attribute is useful in parts of the
> boot loader and probably in security-related functions.
>
>
>> diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
>> index 9cdc03c861cb..e370f6d6459e 100644
>> --- a/sys/sys/cdefs.h
>> +++ b/sys/sys/cdefs.h
>> @@ -396,6 +396,14 @@
>> #define __unreachable() ((void)0)
>> #endif
>>
>> +#if __has_attribute(optnone)
>> +#define __no_optimization __attribute__((optnone))
>> +#elif __has_attribute(optimize)
>> +#define __no_optimization __attribute__((optimize(0)))
>> +#else
>> +#define __no_optimization
>> +#endif
>
> I think the second one is wrong though: 'optimize' doesn't appear to
> be a valid clang attribute. GCC uses an optimize("O0") pragma, but it
> is not an attribute and __has_attribute doesn't work for GCC anyways.
>
Bah, I found it in the GCC 4.4 Release Notes.
Fopr GCC you have to check __GNUC_PREREQ__(4, 4) instead __has_attribute().
Cheers,
Pedro.
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