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

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Message-ID: <20170622223113.GD52338@google.com>
Date:   Thu, 22 Jun 2017 15:31:13 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Michael Davidson <md@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.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

(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;