Index: llvm/trunk/CMakeLists.txt
===================================================================
--- llvm/trunk/CMakeLists.txt
+++ llvm/trunk/CMakeLists.txt
@@ -715,6 +715,9 @@
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/llvm-config.h.cmake
   ${LLVM_INCLUDE_DIR}/llvm/Config/llvm-config.h)
 configure_file(
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/Config/abi-breaking.h.cmake
+  ${LLVM_INCLUDE_DIR}/llvm/Config/abi-breaking.h)
+configure_file(
   ${LLVM_MAIN_INCLUDE_DIR}/llvm/Support/DataTypes.h.cmake
   ${LLVM_INCLUDE_DIR}/llvm/Support/DataTypes.h)
 
Index: llvm/trunk/include/llvm/ADT/EpochTracker.h
===================================================================
--- llvm/trunk/include/llvm/ADT/EpochTracker.h
+++ llvm/trunk/include/llvm/ADT/EpochTracker.h
@@ -16,6 +16,7 @@
 #ifndef LLVM_ADT_EPOCH_TRACKER_H
 #define LLVM_ADT_EPOCH_TRACKER_H
 
+#include "llvm/Config/abi-breaking.h"
 #include "llvm/Config/llvm-config.h"
 
 #include <cstdint>
Index: llvm/trunk/include/llvm/ADT/ilist_node_options.h
===================================================================
--- llvm/trunk/include/llvm/ADT/ilist_node_options.h
+++ llvm/trunk/include/llvm/ADT/ilist_node_options.h
@@ -10,6 +10,7 @@
 #ifndef LLVM_ADT_ILIST_NODE_OPTIONS_H
 #define LLVM_ADT_ILIST_NODE_OPTIONS_H
 
+#include "llvm/Config/abi-breaking.h"
 #include "llvm/Config/llvm-config.h"
 
 #include <type_traits>
Index: llvm/trunk/include/llvm/Config/abi-breaking.h.cmake
===================================================================
--- llvm/trunk/include/llvm/Config/abi-breaking.h.cmake
+++ llvm/trunk/include/llvm/Config/abi-breaking.h.cmake
@@ -0,0 +1,39 @@
+/*===------- llvm/Config/abi-breaking.h - llvm configuration -------*- C -*-===*/
+/*                                                                            */
+/*                     The LLVM Compiler Infrastructure                       */
+/*                                                                            */
+/* This file is distributed under the University of Illinois Open Source      */
+/* License. See LICENSE.TXT for details.                                      */
+/*                                                                            */
+/*===----------------------------------------------------------------------===*/
+
+/* This file controls the C++ ABI break introduced in LLVM public header. */
+
+#ifndef LLVM_ABI_BREAKING_CHECKS_H
+#define LLVM_ABI_BREAKING_CHECKS_H
+
+/* Define to enable checks that alter the LLVM C++ ABI */
+#cmakedefine01 LLVM_ENABLE_ABI_BREAKING_CHECKS
+
+// ABI_BREAKING_CHECKS protection: provides link-time failure when clients build
+// mismatch with LLVM
+#if defined(_MSC_VER)
+// Use pragma with MSVC
+#define LLVM_XSTR(s) LLVM_STR(s)
+#define LLVM_STR(s) #s
+#pragma detect_mismatch("LLVM_ENABLE_ABI_BREAKING_CHECKS", LLVM_XSTR(LLVM_ENABLE_ABI_BREAKING_CHECKS))
+#undef LLVM_XSTR
+#undef LLVM_STR
+#elif defined(__cplusplus)
+namespace llvm {
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
+extern int EnableABIBreakingChecks;
+__attribute__((weak, visibility ("hidden"))) int *VerifyEnableABIBreakingChecks = &EnableABIBreakingChecks;
+#else
+extern int DisableABIBreakingChecks;
+__attribute__((weak, visibility ("hidden"))) int *VerifyDisableABIBreakingChecks = &DisableABIBreakingChecks;
+#endif
+}
+#endif // _MSC_VER
+
+#endif
Index: llvm/trunk/include/llvm/Config/config.h.cmake
===================================================================
--- llvm/trunk/include/llvm/Config/config.h.cmake
+++ llvm/trunk/include/llvm/Config/config.h.cmake
@@ -333,9 +333,6 @@
 /* Doesn't use `cmakedefine` because it is allowed to be empty. */
 #define LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}"
 
-/* Define to enable checks that alter the LLVM C++ ABI */
-#cmakedefine01 LLVM_ENABLE_ABI_BREAKING_CHECKS
-
 /* Define if threads enabled */
 #cmakedefine01 LLVM_ENABLE_THREADS
 
Index: llvm/trunk/include/llvm/Config/llvm-config.h.cmake
===================================================================
--- llvm/trunk/include/llvm/Config/llvm-config.h.cmake
+++ llvm/trunk/include/llvm/Config/llvm-config.h.cmake
@@ -20,9 +20,6 @@
 /* Target triple LLVM will generate code for by default */
 #cmakedefine LLVM_DEFAULT_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}"
 
-/* Define to enable checks that alter the LLVM C++ ABI */
-#cmakedefine01 LLVM_ENABLE_ABI_BREAKING_CHECKS
-
 /* Define if threads enabled */
 #cmakedefine01 LLVM_ENABLE_THREADS
 
Index: llvm/trunk/include/llvm/Support/Error.h
===================================================================
--- llvm/trunk/include/llvm/Support/Error.h
+++ llvm/trunk/include/llvm/Support/Error.h
@@ -18,6 +18,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Config/abi-breaking.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/raw_ostream.h"
Index: llvm/trunk/lib/Support/Error.cpp
===================================================================
--- llvm/trunk/lib/Support/Error.cpp
+++ llvm/trunk/lib/Support/Error.cpp
@@ -112,3 +112,18 @@
 }
 
 }
+
+#ifndef _MSC_VER
+namespace llvm {
+
+// One of these two variables will be referenced by a symbol defined in
+// llvm-config.h. We provide a link-time (or load time for DSO) failure when
+// there is a mismatch in the build configuration of the API client and LLVM.
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
+int EnableABIBreakingChecks;
+#else
+int DisableABIBreakingChecks;
+#endif
+
+} // end namespace llvm
+#endif
\ No newline at end of file