linux-kernel - Re: [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c

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Message-ID: <76723246-ebb4-9bc3-ecc6-e649deb3280f@zytor.com>
Date:   Thu, 22 Jun 2017 15:37:23 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Matthias Kaehlcke <mka@...omium.org>,
        Michael Davidson <md@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c

On 06/22/17 15:31, Matthias Kaehlcke wrote:
> (removed some non-x86 lists and folks from recipients)
> 
> El Thu, Mar 16, 2017 at 05:15:17PM -0700 Michael Davidson ha dit:
> 
>> undef memcpy and friends in boot/string.c so that the functions
>> defined here will have the correct names, otherwise we end up
>> up trying to redefine __builtin_memcpy etc.
>> Surprisingly, gcc allows this (and, helpfully, discards the
>> __builtin_ prefix from the function name when compiling it),
>> but clang does not.
>>
>> Adding these #undef's appears to preserve what I assume was
>> the original intent of the code.
> 
> Any comments on this patch?
> 
>> Signed-off-by: Michael Davidson <md@...gle.com>
>> ---
>>  arch/x86/boot/string.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>>
>> diff --git a/arch/x86/boot/string.c b/arch/x86/boot/string.c
>> index 5457b02fc050..b40266850869 100644
>> --- a/arch/x86/boot/string.c
>> +++ b/arch/x86/boot/string.c
>> @@ -16,6 +16,15 @@
>>  #include "ctype.h"
>>  #include "string.h"
>>  
>> +/*
>> + * Undef these macros so that the functions that we provide
>> + * here will have the correct names regardless of how string.h
>> + * may have chosen to #define them.
>> + */
>> +#undef memcpy
>> +#undef memset
>> +#undef memcmp
>> +
>>  int memcmp(const void *s1, const void *s2, size_t len)
>>  {
>>  	bool diff;

Acked-by: H. Peter Anvin <hpa@...or.com>

	-hpa