Index: lib/asan/CMakeLists.txt
===================================================================
--- lib/asan/CMakeLists.txt
+++ lib/asan/CMakeLists.txt
@@ -77,7 +77,7 @@
 add_compiler_rt_object_libraries(RTAsan_dynamic
   OS ${SANITIZER_COMMON_SUPPORTED_OS}
   ARCHS ${ASAN_SUPPORTED_ARCH}
-  SOURCES ${ASAN_SOURCES} ${ASAN_CXX_SOURCES}
+  SOURCES ${ASAN_SOURCES} ${ASAN_CXX_SOURCES} asan_win_coverage_interception.cc
   CFLAGS ${ASAN_DYNAMIC_CFLAGS}
   DEFS ${ASAN_DYNAMIC_DEFINITIONS})
 
Index: lib/asan/asan_win_coverage_interception.cc
===================================================================
--- /dev/null
+++ lib/asan/asan_win_coverage_interception.cc
@@ -0,0 +1,84 @@
+//===-- asan_win_coverage_interception.cc ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of Sanitizer Coverage for Windows.
+//
+// This module should be statically linked to the Asan dll library in order to
+// delegate the calls of weak functions to the implementation in the main
+// executable when possible. (Based on: asan_win_dll_thunk.cc)
+//===----------------------------------------------------------------------===//
+
+#ifdef _WIN32
+#include "interception/interception.h"
+#include "sanitizer_common/sanitizer_platform_interceptors.h"
+#include "sanitizer_common/sanitizer_interface_internal.h"
+
+#ifdef _M_IX86
+#define WINAPI __stdcall
+#else
+#define WINAPI
+#endif
+
+// Interception helper functions and macros.
+extern "C" {
+void *WINAPI GetModuleHandleA(const char *module_name);
+void *WINAPI GetProcAddress(void *module, const char *proc_name);
+void abort();
+}
+
+using __sanitizer::uptr;
+using __sanitizer::u32;
+
+// Try to get a pointer to real_function in the main module and override
+// dll_function with that pointer. If the function isn't found, nothing changes.
+static void interceptWhenPossible(uptr dll_function, const char *real_function){
+  uptr real = __interception::InternalGetProcAddress(
+    (void *)GetModuleHandleA(0), real_function);
+  if (real && !__interception::OverrideFunction((uptr)dll_function, real, 0))
+    abort();
+}
+
+// Override default functions with implementation provided by users.
+#define INTERCEPT_WEAK(Name)                                                   \
+  interceptWhenPossible((uptr) WEAK_DEF_NAME(Name), #Name);
+
+static int coverage_init() {
+  // We need to intercept weak functions from Sanitizer Coverage in order to
+  // delegate the calls to the implementation in the main executable when
+  // non-defult implementations are provided.
+  INTERCEPT_WEAK(__sanitizer_cov_trace_cmp)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_cmp1)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_cmp2)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_cmp4)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_cmp8)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_switch)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_div4)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_div8)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_gep)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_pc_indir)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_pc_guard)
+  INTERCEPT_WEAK(__sanitizer_cov_trace_pc_guard_init)
+  // In DLLs, the callbacks are expected to return 0,
+  // otherwise CRT initialization fails.
+  return 0;
+}
+
+#pragma section(".CRT$XIB", long, read)  // NOLINT
+__declspec(allocate(".CRT$XIB")) int (*__coverage_preinit)() = coverage_init;
+
+static void WINAPI coverage_thread_init(void *mod, unsigned long reason,
+                                        void *reserved) {
+  if (reason == /*DLL_PROCESS_ATTACH=*/1) coverage_init();
+}
+
+#pragma section(".CRT$XLAB", long, read)  // NOLINT
+__declspec(allocate(".CRT$XLAB")) void (WINAPI *__coverage_tls_init)(void *,
+    unsigned long, void *) = coverage_thread_init;
+
+#endif // _WIN32