Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -225,6 +225,17 @@
 # Warnings to turn off for all libraries, not just sanitizers.
 append_string_if(COMPILER_RT_HAS_WUNUSED_PARAMETER_FLAG -Wno-unused-parameter CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
 
+if (CMAKE_LINKER MATCHES "link.exe$")
+  # Silence MSVC linker warnings caused by empty object files. The
+  # sanitizer libraries intentionally use ifdefs that result in empty
+  # files, rather than skipping these files in the build system.
+  # Ideally, we would pass this flag only for the libraries that need
+  # it, but CMake doesn't seem to have a way to set linker flags for
+  # individual static libraries, so we enable the suppression flag for
+  # the whole compiler-rt project.
+  append("/IGNORE:4221" CMAKE_STATIC_LINKER_FLAGS)
+endif()
+
 add_subdirectory(include)
 
 set(COMPILER_RT_LIBCXX_PATH ${LLVM_MAIN_SRC_DIR}/projects/libcxx)
Index: cmake/Modules/AddCompilerRT.cmake
===================================================================
--- cmake/Modules/AddCompilerRT.cmake
+++ cmake/Modules/AddCompilerRT.cmake
@@ -136,10 +136,18 @@
       if(type STREQUAL "STATIC")
         set(libname "${name}-${arch}")
         set(output_name_${libname} ${libname}${COMPILER_RT_OS_SUFFIX})
+	# We add empty files to archives, which makes MSVC's linker complain
+	# about not defining any previously undefined public symbols. Since
+	# we're doing that on purpose (it simplifies the build configuration),
+	# those warnings would only clutter the build diagnostics, so we
+	# suppress them.
+	# if(CMAKE_LINKER MATCHES "link.exe$")
+	  set(extra_linkflags_${libname} "/IGNORE:4221")
+	# endif()
       else()
         set(libname "${name}-dynamic-${arch}")
         set(extra_cflags_${libname} ${TARGET_${arch}_CFLAGS} ${LIB_CFLAGS})
-        set(extra_linkflags_${libname} ${TARGET_${arch}_LINKFLAGS} ${LIB_LINKFLAGS})
+        set(extra_linkflags_${libname} ${TARGET_${arch}_LINKFLAGS} ${LIB_LINKFLAGS} "/IGNORE:4221")
         if(WIN32)
           set(output_name_${libname} ${name}_dynamic-${arch}${COMPILER_RT_OS_SUFFIX})
         else()
@@ -188,7 +196,7 @@
 
     add_library(${libname} ${type} ${sources_${libname}})
     set_target_compile_flags(${libname} ${extra_cflags_${libname}})
-    set_target_link_flags(${libname} ${extra_linkflags_${libname}})
+    set_target_link_flags(${libname} ${extra_linkflags_${libname}} "/IGNORE:4221")
     set_property(TARGET ${libname} APPEND PROPERTY
                 COMPILE_DEFINITIONS ${LIB_DEFS})
     set_target_output_directories(${libname} ${COMPILER_RT_LIBRARY_OUTPUT_DIR})
@@ -243,7 +251,7 @@
 # when cross compiling, COMPILER_RT_TEST_COMPILER_CFLAGS help
 # in compilation and linking of unittests.
 string(REPLACE " " ";" COMPILER_RT_UNITTEST_CFLAGS "${COMPILER_RT_TEST_COMPILER_CFLAGS}")
-set(COMPILER_RT_UNITTEST_LINKFLAGS ${COMPILER_RT_UNITTEST_CFLAGS})
+set(COMPILER_RT_UNITTEST_LINKFLAGS ${COMPILER_RT_UNITTEST_CFLAGS} "/IGNORE:4221")
 
 # Unittests support.
 set(COMPILER_RT_GTEST_PATH ${LLVM_MAIN_SRC_DIR}/utils/unittest/googletest)
@@ -310,7 +318,7 @@
   add_custom_target(${test_name}
     COMMAND ${COMPILER_RT_TEST_COMPILER} ${TEST_OBJECTS}
             -o "${output_bin}"
-            ${TEST_LINK_FLAGS}
+            ${TEST_LINK_FLAGS} "/IGNORE:4221"
     DEPENDS ${TEST_DEPS})
   set_target_properties(${test_name} PROPERTIES FOLDER "Compiler-RT Tests")
 
Index: lib/asan/CMakeLists.txt
===================================================================
--- lib/asan/CMakeLists.txt
+++ lib/asan/CMakeLists.txt
@@ -38,7 +38,7 @@
 set(ASAN_CFLAGS ${SANITIZER_COMMON_CFLAGS})
 append_rtti_flag(OFF ASAN_CFLAGS)
 
-set(ASAN_DYNAMIC_LINK_FLAGS)
+set(ASAN_DYNAMIC_LINK_FLAGS "/IGNORE:4221")
 
 if(ANDROID)
 # On Android, -z global does not do what it is documented to do.
@@ -184,6 +184,7 @@
               RTUbsan_cxx
       CFLAGS ${ASAN_DYNAMIC_CFLAGS}
       LINKFLAGS ${ASAN_DYNAMIC_LINK_FLAGS}
+                "/IGNORE:4221"
                 ${VERSION_SCRIPT_FLAG}
       LINK_LIBS ${ASAN_DYNAMIC_LIBS}
       DEFS ${ASAN_DYNAMIC_DEFINITIONS}
Index: lib/asan/tests/CMakeLists.txt
===================================================================
--- lib/asan/tests/CMakeLists.txt
+++ lib/asan/tests/CMakeLists.txt
@@ -66,6 +66,16 @@
   list(APPEND ASAN_UNITTEST_COMMON_CFLAGS -fno-exceptions -DGTEST_HAS_SEH=0)
 endif()
 
+# We add empty files to archives, which makes MSVC's linker complain
+# about not defining any previously undefined public symbols. Since
+# we're doing that on purpose (it simplifies the build configuration),
+# those warnings would only clutter the build diagnostics, so we
+# suppress them.
+# if(CMAKE_LINKER MATCHES "link.exe$")
+  set(SUPPRESS_NO_NEW_SYMBOLS_WARNING "/IGNORE:4221")
+  list(APPEND ASAN_UNITTEST_COMMON_LINKFLAGS ${SUPPRESS_NO_NEW_SYMBOLS_WARNING})
+# endif()
+
 set(ASAN_BLACKLIST_FILE "${CMAKE_CURRENT_SOURCE_DIR}/asan_test.ignore")
 set(ASAN_UNITTEST_INSTRUMENTED_CFLAGS
   ${ASAN_UNITTEST_COMMON_CFLAGS}
@@ -168,6 +178,7 @@
                        OBJECTS ${TEST_OBJECTS}
                        DEPS ${TEST_DEPS}
                        LINK_FLAGS ${TEST_LINKFLAGS}
+		                  /IGNORE:4221
                                   ${TARGET_LINK_FLAGS})
 endmacro()
 
@@ -265,7 +276,7 @@
     add_asan_test(AsanDynamicUnitTests "Asan-${arch}${kind}-Dynamic-Test"
                   ${arch} ${kind} SUBDIR "dynamic"
                   OBJECTS ${ASAN_INST_DYNAMIC_TEST_OBJECTS}
-                  LINKFLAGS ${ASAN_DYNAMIC_UNITTEST_INSTRUMENTED_LINKFLAGS})
+                  LINKFLAGS ${ASAN_DYNAMIC_UNITTEST_INSTRUMENTED_LINKFLAGS} "/IGNORE:4221")
   endif()
 
   # Add static ASan runtime that will be linked with uninstrumented tests.
@@ -290,9 +301,18 @@
       $<TARGET_OBJECTS:RTUbsan_cxx.${arch}>)
   endif()
   add_library(${ASAN_TEST_RUNTIME} STATIC ${ASAN_TEST_RUNTIME_OBJECTS})
+  # We add empty files to archives, which makes MSVC's linker complain
+  # about not defining any previously undefined public symbols. Since
+  # we're doing that on purpose (it simplifies the build configuration),
+  # those warnings would only clutter the build diagnostics, so we
+  # suppress them.
+  if(CMAKE_LINKER MATCHES "link.exe$")
+    set(SUPPRESS_NO_NEW_SYMBOLS_WARNING "/IGNORE:4221")
+  endif()
   set_target_properties(${ASAN_TEST_RUNTIME} PROPERTIES
     ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}
-    FOLDER "Compiler-RT Runtime tests")
+    FOLDER "Compiler-RT Runtime tests"
+    LINK_FLAGS "/IGNORE:4221")
   # Uninstrumented tests.
   set(ASAN_NOINST_TEST_OBJECTS)
   foreach(src ${ASAN_NOINST_TEST_SOURCES})
@@ -302,7 +322,7 @@
   add_asan_test(AsanUnitTests "Asan-${arch}${kind}-Noinst-Test"
                 ${arch} ${kind} SUBDIR "default"
                 OBJECTS ${ASAN_NOINST_TEST_OBJECTS}
-                LINKFLAGS ${ASAN_UNITTEST_NOINST_LINKFLAGS}
+                LINKFLAGS ${ASAN_UNITTEST_NOINST_LINKFLAGS} "/IGNORE:4221"
                 WITH_TEST_RUNTIME)
 
   # Benchmarks.
@@ -314,7 +334,7 @@
   add_asan_test(AsanBenchmarks "Asan-${arch}${kind}-Benchmark"
                 ${arch} ${kind} SUBDIR "default"
                 OBJECTS ${ASAN_BENCHMARKS_OBJECTS}
-                LINKFLAGS ${ASAN_UNITTEST_INSTRUMENTED_LINKFLAGS})
+                LINKFLAGS ${ASAN_UNITTEST_INSTRUMENTED_LINKFLAGS} "/IGNORE:4221")
 endmacro()
 
 if(COMPILER_RT_CAN_EXECUTE_TESTS AND NOT ANDROID)
@@ -342,7 +362,7 @@
       ${COMPILER_RT_GTEST_SOURCE}
       ${ASAN_NOINST_TEST_SOURCES})
     set_target_compile_flags(AsanNoinstTest ${ASAN_UNITTEST_COMMON_CFLAGS})
-    set_target_link_flags(AsanNoinstTest ${ASAN_UNITTEST_NOINST_LINKFLAGS})
+    set_target_link_flags(AsanNoinstTest ${ASAN_UNITTEST_NOINST_LINKFLAGS} "/IGNORE:4221")
     target_link_libraries(AsanNoinstTest ${ASAN_UNITTEST_NOINST_LIBS})
 
     # Test with ASan instrumentation. Link with ASan dynamic runtime.
@@ -350,7 +370,7 @@
       ${COMPILER_RT_GTEST_SOURCE}
       ${ASAN_INST_TEST_SOURCES})
     set_target_compile_flags(AsanTest ${ASAN_UNITTEST_INSTRUMENTED_CFLAGS})
-    set_target_link_flags(AsanTest ${ASAN_UNITTEST_INSTRUMENTED_LINKFLAGS})
+    set_target_link_flags(AsanTest ${ASAN_UNITTEST_INSTRUMENTED_LINKFLAGS} "/IGNORE:4221")
     target_link_libraries(AsanTest ${ASAN_UNITTEST_INSTRUMENTED_LIBS})
 
     # Setup correct output directory and link flags.
Index: lib/ubsan/CMakeLists.txt
===================================================================
--- lib/ubsan/CMakeLists.txt
+++ lib/ubsan/CMakeLists.txt
@@ -78,7 +78,9 @@
     set(UBSAN_CXX_SOURCES ${UBSAN_CXXABI_SOURCES})
   else()
     # Dummy target if we don't have C++ ABI library.
-    file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/cxx_dummy.cc "")
+    # It contains a dummy function so that linkers won't complain about the
+    # object file not adding any symbols.
+    file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/cxx_dummy.cc "int dummy_func() { return 0; }")
     set(UBSAN_CXX_SOURCES ${CMAKE_CURRENT_BINARY_DIR}/cxx_dummy.cc)
   endif()