[ASan/Win] Add an extra thunk.lib to handle stack-use-after-return option

With this patch, "check-asan" passes all the tests with both MT and MD ASan RTL if you set COMPILER_RT_BUILD_SHARED_ASAN to ON
(PR20214)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@216447 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 36 insertions, 0 deletions

diff --git a/lib/asan/CMakeLists.txt b/lib/asan/CMakeLists.txt
index a304ff1ed..09407e866 100644
--- a/lib/asan/CMakeLists.txt
+++ b/lib/asan/CMakeLists.txt
@@ -187,6 +187,11 @@ else()
         CFLAGS ${ASAN_CFLAGS} -DASAN_DLL_THUNK
         DEFS ${ASAN_COMMON_DEFINITIONS})
       add_dependencies(asan clang_rt.asan_dll_thunk-${arch})
+      add_compiler_rt_runtime(clang_rt.asan_uar_thunk-${arch} ${arch} STATIC
+        SOURCES asan_win_uar_thunk.cc
+        CFLAGS ${ASAN_CFLAGS} -DASAN_UAR_THUNK
+        DEFS ${ASAN_COMMON_DEFINITIONS})
+      add_dependencies(asan clang_rt.asan_uar_thunk-${arch})
     endif()
   endforeach()
 endif()
diff --git a/lib/asan/asan_win_uar_thunk.cc b/lib/asan/asan_win_uar_thunk.cc
new file mode 100644
index 000000000..27c977ac4
--- /dev/null
+++ b/lib/asan/asan_win_uar_thunk.cc
@@ -0,0 +1,31 @@
+//===-- asan_win_uar_thunk.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 AddressSanitizer, an address sanity checker.
+//
+// This file defines a copy of __asan_option_detect_stack_use_after_return that
+// should be used when linking an MD runtime with a set of object files on
+// Windows.
+//
+// The ASan MD runtime dllexports this variable, so normally we would dllimport
+// it in each TU.  Unfortunately, in general we don't know
+// if a given TU is going to be used with a MT or MD runtime.
+//===----------------------------------------------------------------------===//
+
+// Only compile this code when buidling asan_uar_thunk.lib
+// Using #ifdef rather than relying on Makefiles etc.
+// simplifies the build procedure.
+#ifdef ASAN_UAR_THUNK
+extern "C" {
+__declspec(dllimport) int __asan_should_detect_stack_use_after_return();
+
+int __asan_option_detect_stack_use_after_return =
+    __asan_should_detect_stack_use_after_return();
+}
+#endif // ASAN_UAR_THUNK