From 8e27c6b3fa864147fe5ebdaccf434192405f4357 Mon Sep 17 00:00:00 2001
From: Jeffrey Walton <noloader@gmail.com>
Date: Fri, 31 May 2019 23:33:17 -0400
Subject: [PATCH] Fix OS X compile with Clang later than 6.0 It looks like
 Apple Clang 6.0 does not provide _blsr_u32 and friends. Later versions of
 Clang defines _blsr_u32 and it causes a stream of warnings.

---
 misc.h | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/misc.h b/misc.h
index 87760617..6bcd554e 100644
--- a/misc.h
+++ b/misc.h
@@ -80,12 +80,21 @@
 # include <immintrin.h>
 #endif  // GCC and BMI
 
-// More LLVM bullshit
+// More LLVM bullshit. Apple Clang 6.0 does not define them.
+// Later version of Clang defines them and results in warnings.
 #if defined(__clang__)
-# define _blsr_u32 __blsr_u32
-# define _blsr_u64 __blsr_u64
-# define _tzcnt_u32 __tzcnt_u32
-# define _tzcnt_u64 __tzcnt_u64
+# ifndef _blsr_u32
+#  define _blsr_u32 __blsr_u32
+# endif
+# ifndef _blsr_u64
+#  define _blsr_u64 __blsr_u64
+# endif
+# ifndef _tzcnt_u32
+#  define _tzcnt_u32 __tzcnt_u32
+# endif
+# ifndef _tzcnt_u64
+#  define _tzcnt_u64 __tzcnt_u64
+# endif
 #endif
 
 #endif  // CRYPTOPP_DOXYGEN_PROCESSING