Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -164,7 +164,15 @@
 set(ALL_ASAN_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64}
     ${MIPS32} ${MIPS64} ${PPC64} ${S390X})
 set(ALL_DFSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64})
-set(ALL_LSAN_SUPPORTED_ARCH ${X86} ${X86_64} ${MIPS64} ${ARM64})
+
+# Darwin does not support 32-bit thread-local storage on ios versions
+# below 9.0. Until the min ios version is bumped to 9.0, lsan will
+# not build for 32-bit darwin targets.
+if(APPLE)
+  set(ALL_LSAN_SUPPORTED_ARCH ${X86_64} ${ARM64})
+else()
+  set(ALL_LSAN_SUPPORTED_ARCH ${X86} ${X86_64} ${MIPS64} ${ARM64})
+endif()
 set(ALL_MSAN_SUPPORTED_ARCH ${X86_64} ${MIPS64} ${ARM64} ${PPC64})
 set(ALL_PROFILE_SUPPORTED_ARCH ${X86} ${X86_64} ${ARM32} ${ARM64} ${PPC64}
     ${MIPS32} ${MIPS64} ${S390X})
@@ -477,6 +485,13 @@
   set(COMPILER_RT_HAS_LSAN FALSE)
 endif()
 
+if(APPLE)
+  option(COMPILER_RT_ENABLE_LSAN_OSX "Enable building LSan for OS X - Experimental" Off)
+  if(COMPILER_RT_ENABLE_LSAN_OSX)
+    set(COMPILER_RT_HAS_LSAN TRUE)
+  endif()
+endif()
+
 if (COMPILER_RT_HAS_SANITIZER_COMMON AND MSAN_SUPPORTED_ARCH AND
     OS_NAME MATCHES "Linux")
   set(COMPILER_RT_HAS_MSAN TRUE)
Index: compiler-rt/trunk/lib/asan/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/lib/asan/CMakeLists.txt
+++ compiler-rt/trunk/lib/asan/CMakeLists.txt
@@ -36,6 +36,11 @@
 include_directories(..)
 
 set(ASAN_CFLAGS ${SANITIZER_COMMON_CFLAGS})
+
+# FIXME(fjricci) - remove this once lsan for darwin is fully enabled
+if(APPLE AND COMPILER_RT_HAS_LSAN)
+  set(ASAN_CFLAGS ${ASAN_CFLAGS} -DCAN_SANITIZE_LEAKS_MAC=1)
+endif()
 append_rtti_flag(OFF ASAN_CFLAGS)
 
 set(ASAN_DYNAMIC_LINK_FLAGS)
@@ -107,6 +112,7 @@
 
 if(APPLE)
   add_weak_symbols("asan" WEAK_SYMBOL_LINK_FLAGS)
+  add_weak_symbols("lsan" WEAK_SYMBOL_LINK_FLAGS)
   add_weak_symbols("ubsan" WEAK_SYMBOL_LINK_FLAGS)
   add_weak_symbols("sanitizer_common" WEAK_SYMBOL_LINK_FLAGS)
 
Index: compiler-rt/trunk/lib/lsan/CMakeLists.txt
===================================================================
--- compiler-rt/trunk/lib/lsan/CMakeLists.txt
+++ compiler-rt/trunk/lib/lsan/CMakeLists.txt
@@ -17,6 +17,10 @@
 
 set(LSAN_SRC_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 
+# FIXME(fjricci) - remove this once lsan for darwin is fully enabled
+if(APPLE AND COMPILER_RT_HAS_LSAN)
+  set(LSAN_CFLAGS ${LSAN_CFLAGS} -DCAN_SANITIZE_LEAKS_MAC=1)
+endif()
 add_compiler_rt_object_libraries(RTLSanCommon
     OS ${SANITIZER_COMMON_SUPPORTED_OS}
     ARCHS ${LSAN_COMMON_SUPPORTED_ARCH}
@@ -25,16 +29,34 @@
 
 if(COMPILER_RT_HAS_LSAN)
   add_compiler_rt_component(lsan)
-  foreach(arch ${LSAN_SUPPORTED_ARCH})
+  if(APPLE)
+    add_weak_symbols("lsan" WEAK_SYMBOL_LINK_FLAGS)
+    add_weak_symbols("sanitizer_common" WEAK_SYMBOL_LINK_FLAGS)
+
     add_compiler_rt_runtime(clang_rt.lsan
-      STATIC
-      ARCHS ${arch}
+      SHARED
+      OS ${SANITIZER_COMMON_SUPPORTED_OS}
+      ARCHS ${LSAN_SUPPORTED_ARCH}
       SOURCES ${LSAN_SOURCES}
-              $<TARGET_OBJECTS:RTInterception.${arch}>
-              $<TARGET_OBJECTS:RTSanitizerCommon.${arch}>
-              $<TARGET_OBJECTS:RTSanitizerCommonLibc.${arch}>
-              $<TARGET_OBJECTS:RTLSanCommon.${arch}>
+      OBJECT_LIBS RTLSanCommon
+                  RTInterception
+                  RTSanitizerCommon
+                  RTSanitizerCommonLibc
       CFLAGS ${LSAN_CFLAGS}
+      LINK_FLAGS ${WEAK_SYMBOL_LINK_FLAGS}
       PARENT_TARGET lsan)
-  endforeach()
+  else()
+    foreach(arch ${LSAN_SUPPORTED_ARCH})
+      add_compiler_rt_runtime(clang_rt.lsan
+        STATIC
+        ARCHS ${arch}
+        SOURCES ${LSAN_SOURCES}
+                $<TARGET_OBJECTS:RTInterception.${arch}>
+                $<TARGET_OBJECTS:RTSanitizerCommon.${arch}>
+                $<TARGET_OBJECTS:RTSanitizerCommonLibc.${arch}>
+                $<TARGET_OBJECTS:RTLSanCommon.${arch}>
+        CFLAGS ${LSAN_CFLAGS}
+        PARENT_TARGET lsan)
+    endforeach()
+  endif()
 endif()
Index: compiler-rt/trunk/lib/lsan/lsan_common.h
===================================================================
--- compiler-rt/trunk/lib/lsan/lsan_common.h
+++ compiler-rt/trunk/lib/lsan/lsan_common.h
@@ -30,8 +30,9 @@
 // To enable LeakSanitizer on new architecture, one need to implement
 // internal_clone function as well as (probably) adjust TLS machinery for
 // new architecture inside sanitizer library.
-#if (SANITIZER_LINUX && !SANITIZER_ANDROID) && (SANITIZER_WORDSIZE == 64) \
-     && (defined(__x86_64__) ||  defined(__mips64) ||  defined(__aarch64__))
+#if (SANITIZER_LINUX && !SANITIZER_ANDROID || CAN_SANITIZE_LEAKS_MAC) \
+     && (SANITIZER_WORDSIZE == 64) && (defined(__x86_64__) \
+     ||  defined(__mips64) ||  defined(__aarch64__))
 #define CAN_SANITIZE_LEAKS 1
 #elif SANITIZER_LINUX && !SANITIZER_ANDROID && defined(__i386__)
 #define CAN_SANITIZE_LEAKS 1
Index: compiler-rt/trunk/lib/lsan/weak_symbols.txt
===================================================================
--- compiler-rt/trunk/lib/lsan/weak_symbols.txt
+++ compiler-rt/trunk/lib/lsan/weak_symbols.txt
@@ -0,0 +1,2 @@
+___lsan_default_suppressions
+___lsan_is_turned_off