[PATCH] D16496: [cfi] Do not emit bit set entry for available_externally vtables.

[Evgeniy Stepanov via cfe-commits]

eugenis created this revision.
eugenis added reviewers: pcc, kcc.
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In the Itanium ABI, vtable may be emitted speculatively as an
available_externally global. Such vtable may not be present at the
link time and should not have a corresponding CFI bit set entry.

Repository:
  rL LLVM

http://reviews.llvm.org/D16496

Files:
  lib/CodeGen/ItaniumCXXABI.cpp
  test/CodeGenCXX/cfi-speculative-vtable.cpp

Index: test/CodeGenCXX/cfi-speculative-vtable.cpp
===================================================================
--- /dev/null
+++ test/CodeGenCXX/cfi-speculative-vtable.cpp
@@ -0,0 +1,14 @@
+// Test that we don't emit a bit set entry for a speculative (available_externally) vtable.
+// This does not happen in the Microsoft ABI.
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -O1 -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck  %s
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -O1 -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -fsanitize-cfi-cross-dso -emit-llvm -o - %s | FileCheck  %s
+
+class A {
+ public:
+  virtual ~A();
+};
+
+A a;
+
+// CHECK: @_ZTV1A ={{.*}} available_externally
+// CHECK-NOT: !{{.*}} = !{!{{.*}}, [4 x i8*]* @_ZTV1A, i64 16}
Index: lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- lib/CodeGen/ItaniumCXXABI.cpp
+++ lib/CodeGen/ItaniumCXXABI.cpp
@@ -1496,7 +1496,8 @@
       DC->getParent()->isTranslationUnit())
     EmitFundamentalRTTIDescriptors();
 
-  CGM.EmitVTableBitSetEntries(VTable, VTLayout);
+  if (!VTable->isDeclarationForLinker())
+    CGM.EmitVTableBitSetEntries(VTable, VTLayout);
 }
 
 bool ItaniumCXXABI::isVirtualOffsetNeededForVTableField(


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