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

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Date:   Thu, 16 Mar 2017 17:15:17 -0700
From:   Michael Davidson <md@...gle.com>
To:     Michal Marek <mmarek@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Shaohua Li <shli@...nel.org>
Cc:     Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>, x86@...nel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-raid@...r.kernel.org,
        Michael Davidson <md@...gle.com>
Subject: [PATCH 4/7] x86, boot, LLVM: #undef memcpy etc in string.c

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.

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;
-- 
2.12.0.367.g23dc2f6d3c-goog