Add link-time detection of LLVM_ABI_BREAKING_CHECKS mismatch (#5380)

The macro LLVM_ENABLE_ABI_BREAKING_CHECKS is moved to a new header
abi-breaking.h, from llvm-config.h. Only headers that are using the
macro are including this new header.

LLVM will define a symbol, either EnableABIBreakingChecks or
DisableABIBreakingChecks depending on the configuration setting for
LLVM_ABI_BREAKING_CHECKS.

The abi-breaking.h header will add weak references to these symbols in
every clients that includes this header. This should ensure that a
mismatch triggers a link failure (or a load time failure for DSO).

On MSVC, the pragma "detect_mismatch" is used instead.

Differential Revision: https://reviews.llvm.org/D26876

llvm-svn: 288082

Co-authored-by: Mehdi Amini <mehdi.amini@apple.com>

CMakeLists.txt

@@ -564,6 +564,9 @@ configure_file(
 configure_file(
   ${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)

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>

include/llvm/ADT/ilist_node.h

@@ -15,6 +15,8 @@
 #ifndef LLVM_ADT_ILIST_NODE_H
 #define LLVM_ADT_ILIST_NODE_H
 
+#include "llvm/Config/abi-breaking.h"
+
 namespace llvm {
 
 template<typename NodeTy>

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

include/llvm/Config/config.h.cmake

@@ -432,10 +432,6 @@
 /* Installation directory for documentation */
 #cmakedefine LLVM_DOCSDIR "${LLVM_DOCSDIR}"
 
-/* Define if LLVM is built with asserts and checks that change the layout of
-   client-visible data structures.  */
-#cmakedefine LLVM_ENABLE_ABI_BREAKING_CHECKS
-
 /* Define if threads enabled */
 #cmakedefine01 LLVM_ENABLE_THREADS
 

include/llvm/Config/llvm-config.h.cmake

@@ -29,10 +29,6 @@
 /* Installation directory for documentation */
 #cmakedefine LLVM_DOCSDIR "${LLVM_DOCSDIR}"
 
-/* Define if LLVM is built with asserts and checks that change the layout of
-   client-visible data structures.  */
-#cmakedefine LLVM_ENABLE_ABI_BREAKING_CHECKS
-
 /* Define if threads enabled */
 #cmakedefine01 LLVM_ENABLE_THREADS
 

include/llvm/Support/ErrorHandling.h

@@ -17,6 +17,7 @@
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Config/abi-breaking.h"
 #include <string>
 
 namespace llvm {

lib/Support/ErrorHandling.cpp

@@ -226,3 +226,18 @@ std::error_code llvm::mapWindowsError(unsigned EV) {
 }
 
 #endif
+
+#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