Index: compiler-rt/trunk/cmake/config-ix.cmake
===================================================================
--- compiler-rt/trunk/cmake/config-ix.cmake
+++ compiler-rt/trunk/cmake/config-ix.cmake
@@ -476,7 +476,7 @@
 endif()
 
 if (COMPILER_RT_HAS_SANITIZER_COMMON AND LSAN_SUPPORTED_ARCH AND
-    OS_NAME MATCHES "Linux|FreeBSD")
+    OS_NAME MATCHES "Darwin|Linux|FreeBSD")
   set(COMPILER_RT_HAS_LSAN TRUE)
 else()
   set(COMPILER_RT_HAS_LSAN FALSE)
Index: compiler-rt/trunk/test/asan/lit.cfg
===================================================================
--- compiler-rt/trunk/test/asan/lit.cfg
+++ compiler-rt/trunk/test/asan/lit.cfg
@@ -38,6 +38,11 @@
   # Also, make sure we do not overwhelm the syslog while testing.
   default_asan_opts = 'abort_on_error=0'
   default_asan_opts += ':log_to_syslog=0'
+
+  # On Darwin, leak checking is not enabled by default. Enable for x86_64
+  # tests to prevent regressions
+  if config.target_arch == 'x86_64':
+    default_asan_opts += ':detect_leaks=1'
 elif config.android:
   # The same as on Darwin, we default to "abort_on_error=1" which slows down
   # testing. Also, all existing tests are using "not" instead of "not --crash"
@@ -215,7 +220,9 @@
   config.available_features.add('fast-unwinder-works')
 
 # Turn on leak detection on 64-bit Linux.
-if config.host_os == 'Linux' and (config.target_arch == 'x86_64' or config.target_arch == 'i386'):
+leak_detection_linux = (config.host_os == 'Linux') and (config.target_arch == 'x86_64' or config.target_arch == 'i386')
+leak_detection_mac = (config.host_os == 'Darwin') and (config.target_arch == 'x86_64')
+if leak_detection_linux or leak_detection_mac:
   config.available_features.add('leak-detection')
 
 # Set LD_LIBRARY_PATH to pick dynamic runtime up properly.
Index: compiler-rt/trunk/test/lsan/lit.common.cfg
===================================================================
--- compiler-rt/trunk/test/lsan/lit.common.cfg
+++ compiler-rt/trunk/test/lsan/lit.common.cfg
@@ -67,9 +67,10 @@
 config.substitutions.append( ("%clang_lsan ", build_invocation(clang_lsan_cflags)) )
 config.substitutions.append( ("%clangxx_lsan ", build_invocation(clang_lsan_cxxflags)) )
 
-# LeakSanitizer tests are currently supported on x86-64 Linux, PowerPC64 Linux, arm Linux, and mips64 Linux only.
+# LeakSanitizer tests are currently supported on x86-64 Linux, PowerPC64 Linux, arm Linux, mips64 Linux, and x86_64 Darwin.
 supported_linux = config.host_os is 'Linux' and config.host_arch in ['x86_64', 'ppc64', 'mips64', 'arm', 'armhf', 'armv7l']
-if not (supported_linux):
+supported_darwin = config.host_os is 'Darwin' and config.target_arch is 'x86_64'
+if not (supported_linux or supported_darwin):
   config.unsupported = True
 
 # Don't support Thumb due to broken fast unwinder