From b1c57f9f5427da09f7e1088b44c05cd26ab8a660 Mon Sep 17 00:00:00 2001
From: Matthew Barr <matthew.barr@intel.com>
Date: Thu, 6 Apr 2017 10:53:28 +1000
Subject: [PATCH] cmake: check for libc++ directly

Rather than trying to infer libc++ use from platform and compiler, just
look for a defined symbol.
---
 CMakeLists.txt    | 4 ++++
 cmake/boost.cmake | 6 ++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index fbcb5399..34405097 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@ set (HS_VERSION ${HS_MAJOR_VERSION}.${HS_MINOR_VERSION}.${HS_PATCH_VERSION})
 set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
+include(CheckCXXSymbolExists)
 INCLUDE (CheckFunctionExists)
 INCLUDE (CheckIncludeFiles)
 INCLUDE (CheckIncludeFileCXX)
@@ -264,6 +265,9 @@ CHECK_FUNCTION_EXISTS(_aligned_malloc HAVE__ALIGNED_MALLOC)
 CHECK_C_COMPILER_FLAG(-fvisibility=hidden HAS_C_HIDDEN)
 CHECK_CXX_COMPILER_FLAG(-fvisibility=hidden HAS_CXX_HIDDEN)
 
+# are we using libc++
+CHECK_CXX_SYMBOL_EXISTS(_LIBCPP_VERSION ciso646 HAVE_LIBCPP)
+
 if (RELEASE_BUILD)
     if (HAS_C_HIDDEN)
         set(EXTRA_C_FLAGS "${EXTRA_C_FLAGS} -fvisibility=hidden")
diff --git a/cmake/boost.cmake b/cmake/boost.cmake
index ff4e2f94..44b4e8ba 100644
--- a/cmake/boost.cmake
+++ b/cmake/boost.cmake
@@ -3,10 +3,8 @@
 set(BOOST_USE_STATIC_LIBS OFF)
 set(BOOST_USE_MULTITHREADED OFF)
 set(BOOST_USE_STATIC_RUNTIME OFF)
-if (CMAKE_SYSTEM_NAME MATCHES "Darwin"
-    OR (CMAKE_SYSTEM_NAME MATCHES "FreeBSD"
-        AND CMAKE_C_COMPILER_ID MATCHES "Clang"))
-    # we need a more recent boost for libc++ used by clang on OSX and FreeBSD
+if (HAVE_LIBCPP)
+    # we need a more recent boost for libc++
     set(BOOST_MINVERSION 1.61.0)
 else ()
     set(BOOST_MINVERSION 1.57.0)