Add support for building with the various sanitizers

When building with ASan, core is also built with ASan enabled (and thus
using a local build is required). The other two sanitizers aren't also
forwarded on to core's settings since they don't need to be.

CMake/RealmCore.cmake

@@ -4,6 +4,10 @@ if(${CMAKE_GENERATOR} STREQUAL "Unix Makefiles")
     set(MAKE_EQUAL_MAKE "MAKE=$(MAKE)")
 endif()
 
+if(SANITIZE_ADDRESS)
+  set(MAKEFLAGS "MAKEFLAGS=EXTRA_CFLAGS=-fsanitize=address EXTRA_LDFLAGS=-fsanitize=address")
+endif()
+
 if (${CMAKE_VERSION} VERSION_GREATER "3.4.0")
     set(USES_TERMINAL_BUILD USES_TERMINAL_BUILD 1)
 endif()
@@ -91,7 +95,7 @@ function(clone_and_build_realm_core branch)
         PREFIX ${core_prefix_directory}
         BUILD_IN_SOURCE 1
         CONFIGURE_COMMAND ""
-        BUILD_COMMAND ${MAKE_EQUAL_MAKE} sh build.sh build
+        BUILD_COMMAND export ${MAKEFLAGS} && ${MAKE_EQUAL_MAKE} sh build.sh build
         INSTALL_COMMAND ""
         ${USES_TERMINAL_BUILD}
         )
@@ -109,7 +113,7 @@ function(build_existing_realm_core core_directory)
         BUILD_IN_SOURCE 1
         BUILD_ALWAYS 1
         CONFIGURE_COMMAND ""
-        BUILD_COMMAND ${MAKE_EQUAL_MAKE} sh build.sh build
+        BUILD_COMMAND export ${MAKEFLAGS} && ${MAKE_EQUAL_MAKE} sh build.sh build
         INSTALL_COMMAND ""
         ${USES_TERMINAL_BUILD}
         )

CMake/Sanitizers.cmake

@@ -0,0 +1,20 @@
+option(SANITIZE_ADDRESS "build with ASan")
+option(SANITIZE_THREAD "build with TSan")
+option(SANITIZE_UNDEFINED "build with UBSan")
+
+if(SANITIZE_ADDRESS)
+    set(SANITIZER_FLAGS "${SANITIZER_FLAGS} -fsanitize=address")
+endif()
+
+if(SANITIZE_THREAD)
+    set(SANITIZER_FLAGS "${SANITIZER_FLAGS} -fsanitize=thread")
+endif()
+
+if(SANITIZE_UNDEFINED)
+    set(SANITIZER_FLAGS "${SANITIZER_FLAGS} -fsanitize=undefined")
+endif()
+
+if(SANITIZE_ADDRESS OR SANITIZE_THREAD OR SANITIZE_UNDEFINED)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${SANITIZER_FLAGS} -fno-omit-frame-pointer")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${SANITIZER_FLAGS}")
+endif()

CMakeLists.txt

@@ -5,6 +5,7 @@ cmake_minimum_required(VERSION 3.2.0)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/CMake")
 
 include(CompilerFlags)
+include(Sanitizers)
 
 include(RealmCore)
 set(REALM_CORE_VERSION "0.97.0" CACHE STRING "")

README.md

@@ -36,6 +36,14 @@ cmake -DREALM_CORE_VERSION=/path/to/realm-core
 
 The given core tree will be built as part of the object store build.
 
+### Building with Sanitizers
+
+The object store can be built using ASan, TSan and/or UBSan by specifying `-DSANITIZE_ADDRESS=1`, `-DSANITIZE_THREAD=1`, or `-DSANITIZE_UNDEFINED=1` when inoking CMake.
+Building with ASan requires specifying a path to core with `-DREAM_CORE_VERSION` as core needs to also be built with ASan enabled.
+
+On OS X, the Xcode-provided copy of Clang only comes with ASan, and using TSan or UBSan requires a custom build of Clang.
+If you have installed Clang as an external Xcode toolchain (using the `install-xcode-toolchain` when building LLVM), note that you'll have to specify `-DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++` when running `cmake` to stop cmake from being too clever.
+
 ## Testing
 
 ```