Add link-time detection of LLVM_ABI_BREAKING_CHECKS mismatch

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

The llvm-config.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.

Reviewers: rnk, jroelofs

Subscribers: llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D26841

llvm-svn: 287352

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Support/Error.cpp b/llvm/lib/Support/Error.cpp
index 7436a1fd38e..f818868b641 100644
--- a/llvm/lib/Support/Error.cpp
+++ b/llvm/lib/Support/Error.cpp
@@ -112,3 +112,19 @@ void report_fatal_error(Error Err, bool GenCrashDiag) {
 }
 
 }
+
+
+#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