Initial implementation of exclusive definition of compiler detection

with emulated definitions.

include/boost/predef/compiler/llvm.h

@@ -1,5 +1,5 @@
 /*
-Copyright Rene Rivera 2008-2013
+Copyright Rene Rivera 2008-2014
 Distributed under the Boost Software License, Version 1.0.
 (See accompanying file LICENSE_1_0.txt or copy at
 http://www.boost.org/LICENSE_1_0.txt)
@@ -8,6 +8,10 @@ http://www.boost.org/LICENSE_1_0.txt)
 #ifndef BOOST_PREDEF_COMPILER_LLVM_H
 #define BOOST_PREDEF_COMPILER_LLVM_H
 
+/* Other compilers that emulate this one need to be detected first. */
+
+#include <boost/predef/compiler/clang.h>
+
 #include <boost/predef/version_number.h>
 #include <boost/predef/make.h>
 
@@ -26,12 +30,18 @@ http://www.boost.org/LICENSE_1_0.txt)
 #define BOOST_COMP_LLVM BOOST_VERSION_NUMBER_NOT_AVAILABLE
 
 #if defined(__llvm__)
-#   undef BOOST_COMP_LLVM
-#   define BOOST_COMP_LLVM BOOST_VERSION_NUMBER_AVAILABLE
+#   define BOOST_COMP_LLVM_DETECTION BOOST_VERSION_NUMBER_AVAILABLE
 #endif
 
-#if BOOST_COMP_LLVM
+#ifdef BOOST_COMP_LLVM_DETECTION
+#   if defined(BOOST_PREDEF_DETAIL_COMP_DETECTED)
+#       define BOOST_COMP_LLVM_EMULATED BOOST_COMP_LLVM_DETECTION
+#   else
+#       undef BOOST_COMP_LLVM
+#       define BOOST_COMP_LLVM BOOST_COMP_LLVM_DETECTION
+#   endif
 #   define BOOST_COMP_LLVM_AVAILABLE
+#   include <boost/predef/detail/comp_detected.h>
 #endif
 
 #define BOOST_COMP_LLVM_NAME "LLVM"
@@ -39,5 +49,10 @@ http://www.boost.org/LICENSE_1_0.txt)
 #include <boost/predef/detail/test.h>
 BOOST_PREDEF_DECLARE_TEST(BOOST_COMP_LLVM,BOOST_COMP_LLVM_NAME)
 
+#ifdef BOOST_COMP_LLVM_EMULATED
+#include <boost/predef/detail/test.h>
+BOOST_PREDEF_DECLARE_TEST(BOOST_COMP_LLVM_EMULATED,BOOST_COMP_LLVM_NAME)
+#endif
+
 
 #endif