rsmith created this revision.
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Herald added a project: clang.
Herald added a subscriber: cfe-commits.
Without this patch, type_info objects for pointers to incomplete classes
compare unequal with libc++ when formed in multiple translation units,
because each translation unit has its own copy of the _ZTS symbol, in
violation of the Itanium ABI's uniqueness rule.
Repository:
rC Clang
https://reviews.llvm.org/D62429
Files:
lib/CodeGen/ItaniumCXXABI.cpp
test/CodeGenCXX/rtti-linkage.cpp
Index: test/CodeGenCXX/rtti-linkage.cpp
===================================================================
--- test/CodeGenCXX/rtti-linkage.cpp
+++ test/CodeGenCXX/rtti-linkage.cpp
@@ -3,27 +3,36 @@
#include <typeinfo>
-// CHECK-BOTH: _ZTSP1C = internal constant
-// CHECK-BOTH: _ZTS1C = internal constant
+// CHECK: _ZTSP1C = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSP1C = linkonce_odr hidden constant
+// CHECK: _ZTS1C = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTS1C = linkonce_odr hidden constant
// CHECK-BOTH: _ZTI1C = internal constant
// CHECK-BOTH: _ZTIP1C = internal constant
-// CHECK-BOTH: _ZTSPP1C = internal constant
+// CHECK: _ZTSPP1C = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSPP1C = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIPP1C = internal constant
-// CHECK-BOTH: _ZTSM1Ci = internal constant
+// CHECK: _ZTSM1Ci = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSM1Ci = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIM1Ci = internal constant
-// CHECK-BOTH: _ZTSPM1Ci = internal constant
+// CHECK: _ZTSPM1Ci = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSPM1Ci = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIPM1Ci = internal constant
-// CHECK-BOTH: _ZTSM1CS_ = internal constant
+// CHECK: _ZTSM1CS_ = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSM1CS_ = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIM1CS_ = internal constant
-// CHECK-BOTH: _ZTSM1CPS_ = internal constant
+// CHECK: _ZTSM1CPS_ = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSM1CPS_ = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIM1CPS_ = internal constant
-// CHECK-BOTH: _ZTSM1A1C = internal constant
+// CHECK: _ZTSM1A1C = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSM1A1C = linkonce_odr hidden constant
// CHECK: _ZTS1A = linkonce_odr constant
// CHECK-WITH-HIDDEN: _ZTS1A = linkonce_odr hidden constant
// CHECK: _ZTI1A = linkonce_odr constant
// CHECK-WITH-HIDDEN: _ZTI1A = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIM1A1C = internal constant
-// CHECK-BOTH: _ZTSM1AP1C = internal constant
+// CHECK: _ZTSM1AP1C = linkonce_odr constant
+// CHECK-WITH-HIDDEN: _ZTSM1AP1C = linkonce_odr hidden constant
// CHECK-BOTH: _ZTIM1AP1C = internal constant
// CHECK-WITH-HIDDEN: _ZTSFN12_GLOBAL__N_11DEvE = internal constant
Index: lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- lib/CodeGen/ItaniumCXXABI.cpp
+++ lib/CodeGen/ItaniumCXXABI.cpp
@@ -3155,18 +3155,6 @@
/// should have for the given type.
static llvm::GlobalVariable::LinkageTypes getTypeInfoLinkage(CodeGenModule &CGM,
QualType Ty) {
- // Itanium C++ ABI 2.9.5p7:
- // In addition, it and all of the intermediate abi::__pointer_type_info
- // structs in the chain down to the abi::__class_type_info for the
- // incomplete class type must be prevented from resolving to the
- // corresponding type_info structs for the complete class type, possibly
- // by making them local static objects. Finally, a dummy class RTTI is
- // generated for the incomplete type that will not resolve to the final
- // complete class RTTI (because the latter need not exist), possibly by
- // making it a local static object.
- if (ContainsIncompleteClassType(Ty))
- return llvm::GlobalValue::InternalLinkage;
-
switch (Ty->getLinkage()) {
case NoLinkage:
case InternalLinkage:
@@ -3184,6 +3172,11 @@
if (const RecordType *Record = dyn_cast<RecordType>(Ty)) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(Record->getDecl());
+ // If the class is incomplete, we're forming the pointee of an incomplete
+ // pointer typeinfo. This linkage will only be used for the type name;
+ // give it linkonce_odr linkage.
+ if (!RD->isCompleteDefinition())
+ return llvm::GlobalValue::LinkOnceODRLinkage;
if (RD->hasAttr<WeakAttr>())
return llvm::GlobalValue::WeakODRLinkage;
if (CGM.getTriple().isWindowsItaniumEnvironment())
@@ -3255,20 +3248,20 @@
llvm::Constant *ItaniumRTTIBuilder::BuildTypeInfo(
QualType Ty,
- llvm::GlobalVariable::LinkageTypes Linkage,
- llvm::GlobalValue::VisibilityTypes Visibility,
+ llvm::GlobalVariable::LinkageTypes TypeNameLinkage,
+ llvm::GlobalValue::VisibilityTypes TypeNameVisibility,
llvm::GlobalValue::DLLStorageClassTypes DLLStorageClass) {
// Add the vtable pointer.
BuildVTablePointer(cast<Type>(Ty));
// And the name.
- llvm::GlobalVariable *TypeName = GetAddrOfTypeName(Ty, Linkage);
+ llvm::GlobalVariable *TypeName = GetAddrOfTypeName(Ty, TypeNameLinkage);
llvm::Constant *TypeNameField;
// If we're supposed to demote the visibility, be sure to set a flag
// to use a string comparison for type_info comparisons.
ItaniumCXXABI::RTTIUniquenessKind RTTIUniqueness =
- CXXABI.classifyRTTIUniqueness(Ty, Linkage);
+ CXXABI.classifyRTTIUniqueness(Ty, TypeNameLinkage);
if (RTTIUniqueness != ItaniumCXXABI::RUK_Unique) {
// The flag is the sign bit, which on ARM64 is defined to be clear
// for global pointers. This is very ARM64-specific.
@@ -3371,6 +3364,28 @@
llvm::Constant *Init = llvm::ConstantStruct::getAnon(Fields);
+ // Itanium C++ ABI 2.9.5p7:
+ // In addition, it and all of the intermediate abi::__pointer_type_info
+ // structs in the chain down to the abi::__class_type_info for the
+ // incomplete class type must be prevented from resolving to the
+ // corresponding type_info structs for the complete class type, possibly
+ // by making them local static objects. Finally, a dummy class RTTI is
+ // generated for the incomplete type that will not resolve to the final
+ // complete class RTTI (because the latter need not exist), possibly by
+ // making it a local static object.
+ //
+ // Two abi::__pbase_type_info objects can always be compared for equality
+ // (i.e. of the types represented) or ordering by comparison of their name
+ // NTBS addresses. In addition, unless either or both have either of the
+ // incomplete flags set, equality can be tested by comparing the type_info
+ // addresses.
+ llvm::GlobalVariable::LinkageTypes TypeInfoLinkage = TypeNameLinkage;
+ llvm::GlobalValue::VisibilityTypes TypeInfoVisibility = TypeNameVisibility;
+ if (ContainsIncompleteClassType(Ty)) {
+ TypeInfoLinkage = llvm::GlobalVariable::InternalLinkage;
+ TypeInfoVisibility = llvm::GlobalValue::DefaultVisibility;
+ }
+
SmallString<256> Name;
llvm::raw_svector_ostream Out(Name);
CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty, Out);
@@ -3378,7 +3393,7 @@
llvm::GlobalVariable *OldGV = M.getNamedGlobal(Name);
llvm::GlobalVariable *GV =
new llvm::GlobalVariable(M, Init->getType(),
- /*Constant=*/true, Linkage, Init, Name);
+ /*Constant=*/true, TypeInfoLinkage, Init, Name);
// If there's already an old global variable, replace it with the new one.
if (OldGV) {
@@ -3411,10 +3426,10 @@
// All of this is to say that it's important that both the type_info
// object and the type_info name be uniqued when weakly emitted.
- TypeName->setVisibility(Visibility);
+ TypeName->setVisibility(TypeNameVisibility);
CGM.setDSOLocal(TypeName);
- GV->setVisibility(Visibility);
+ GV->setVisibility(TypeInfoVisibility);
CGM.setDSOLocal(GV);
TypeName->setDLLStorageClass(DLLStorageClass);
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