Enable DLL attribute propagation on explicit instantiation definitions (PR23770)

This is a follow-up to r225570 which enabled adding DLL attributes when a
class template goes from explicit instantiation declaration to explicit
instantiation definition.

llvm-svn: 239375

clang/include/clang/Sema/Sema.h

@@ -5110,6 +5110,10 @@ public:
                             bool AnyErrors);
 
   void checkClassLevelDLLAttribute(CXXRecordDecl *Class);
+  void propagateDLLAttrToBaseClassTemplate(
+      CXXRecordDecl *Class, Attr *ClassAttr,
+      ClassTemplateSpecializationDecl *BaseTemplateSpec,
+      SourceLocation BaseLoc);
   void CheckCompletedCXXClass(CXXRecordDecl *Record);
   void ActOnFinishCXXMemberSpecification(Scope* S, SourceLocation RLoc,
                                          Decl *TagDecl,

clang/lib/Sema/SemaDeclCXX.cpp

@@ -1345,61 +1345,6 @@ static bool findCircularInheritance(const CXXRecordDecl *Class,
   return false;
 }
 
-/// \brief Perform propagation of DLL attributes from a derived class to a
-/// templated base class for MS compatibility.
-static void propagateDLLAttrToBaseClassTemplate(
-    Sema &S, CXXRecordDecl *Class, Attr *ClassAttr,
-    ClassTemplateSpecializationDecl *BaseTemplateSpec, SourceLocation BaseLoc) {
-  if (getDLLAttr(
-          BaseTemplateSpec->getSpecializedTemplate()->getTemplatedDecl())) {
-    // If the base class template has a DLL attribute, don't try to change it.
-    return;
-  }
-
-  auto TSK = BaseTemplateSpec->getSpecializationKind();
-  if (!getDLLAttr(BaseTemplateSpec) &&
-      (TSK == TSK_Undeclared || TSK == TSK_ExplicitInstantiationDeclaration ||
-       TSK == TSK_ImplicitInstantiation)) {
-    // The template hasn't been instantiated yet (or it has, but only as an
-    // explicit instantiation declaration or implicit instantiation, which means
-    // we haven't codegenned any members yet), so propagate the attribute.
-    auto *NewAttr = cast<InheritableAttr>(ClassAttr->clone(S.getASTContext()));
-    NewAttr->setInherited(true);
-    BaseTemplateSpec->addAttr(NewAttr);
-
-    // If the template is already instantiated, checkDLLAttributeRedeclaration()
-    // needs to be run again to work see the new attribute. Otherwise this will
-    // get run whenever the template is instantiated.
-    if (TSK != TSK_Undeclared)
-      S.checkClassLevelDLLAttribute(BaseTemplateSpec);
-
-    return;
-  }
-
-  if (getDLLAttr(BaseTemplateSpec)) {
-    // The template has already been specialized or instantiated with an
-    // attribute, explicitly or through propagation. We should not try to change
-    // it.
-    return;
-  }
-
-  // The template was previously instantiated or explicitly specialized without
-  // a dll attribute, It's too late for us to add an attribute, so warn that
-  // this is unsupported.
-  S.Diag(BaseLoc, diag::warn_attribute_dll_instantiated_base_class)
-      << BaseTemplateSpec->isExplicitSpecialization();
-  S.Diag(ClassAttr->getLocation(), diag::note_attribute);
-  if (BaseTemplateSpec->isExplicitSpecialization()) {
-    S.Diag(BaseTemplateSpec->getLocation(),
-           diag::note_template_class_explicit_specialization_was_here)
-        << BaseTemplateSpec;
-  } else {
-    S.Diag(BaseTemplateSpec->getPointOfInstantiation(),
-           diag::note_template_class_instantiation_was_here)
-        << BaseTemplateSpec;
-  }
-}
-
 /// \brief Check the validity of a C++ base class specifier.
 ///
 /// \returns a new CXXBaseSpecifier if well-formed, emits diagnostics
@@ -1471,8 +1416,8 @@ Sema::CheckBaseSpecifier(CXXRecordDecl *Class,
     if (Attr *ClassAttr = getDLLAttr(Class)) {
       if (auto *BaseTemplate = dyn_cast_or_null<ClassTemplateSpecializationDecl>(
               BaseType->getAsCXXRecordDecl())) {
-        propagateDLLAttrToBaseClassTemplate(*this, Class, ClassAttr,
-                                            BaseTemplate, BaseLoc);
+        propagateDLLAttrToBaseClassTemplate(Class, ClassAttr, BaseTemplate,
+                                            BaseLoc);
       }
     }
   }
@@ -4884,6 +4829,61 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
   }
 }
 
+/// \brief Perform propagation of DLL attributes from a derived class to a
+/// templated base class for MS compatibility.
+void Sema::propagateDLLAttrToBaseClassTemplate(
+    CXXRecordDecl *Class, Attr *ClassAttr,
+    ClassTemplateSpecializationDecl *BaseTemplateSpec, SourceLocation BaseLoc) {
+  if (getDLLAttr(
+          BaseTemplateSpec->getSpecializedTemplate()->getTemplatedDecl())) {
+    // If the base class template has a DLL attribute, don't try to change it.
+    return;
+  }
+
+  auto TSK = BaseTemplateSpec->getSpecializationKind();
+  if (!getDLLAttr(BaseTemplateSpec) &&
+      (TSK == TSK_Undeclared || TSK == TSK_ExplicitInstantiationDeclaration ||
+       TSK == TSK_ImplicitInstantiation)) {
+    // The template hasn't been instantiated yet (or it has, but only as an
+    // explicit instantiation declaration or implicit instantiation, which means
+    // we haven't codegenned any members yet), so propagate the attribute.
+    auto *NewAttr = cast<InheritableAttr>(ClassAttr->clone(getASTContext()));
+    NewAttr->setInherited(true);
+    BaseTemplateSpec->addAttr(NewAttr);
+
+    // If the template is already instantiated, checkDLLAttributeRedeclaration()
+    // needs to be run again to work see the new attribute. Otherwise this will
+    // get run whenever the template is instantiated.
+    if (TSK != TSK_Undeclared)
+      checkClassLevelDLLAttribute(BaseTemplateSpec);
+
+    return;
+  }
+
+  if (getDLLAttr(BaseTemplateSpec)) {
+    // The template has already been specialized or instantiated with an
+    // attribute, explicitly or through propagation. We should not try to change
+    // it.
+    return;
+  }
+
+  // The template was previously instantiated or explicitly specialized without
+  // a dll attribute, It's too late for us to add an attribute, so warn that
+  // this is unsupported.
+  Diag(BaseLoc, diag::warn_attribute_dll_instantiated_base_class)
+      << BaseTemplateSpec->isExplicitSpecialization();
+  Diag(ClassAttr->getLocation(), diag::note_attribute);
+  if (BaseTemplateSpec->isExplicitSpecialization()) {
+    Diag(BaseTemplateSpec->getLocation(),
+           diag::note_template_class_explicit_specialization_was_here)
+        << BaseTemplateSpec;
+  } else {
+    Diag(BaseTemplateSpec->getPointOfInstantiation(),
+           diag::note_template_class_instantiation_was_here)
+        << BaseTemplateSpec;
+  }
+}
+
 /// \brief Perform semantic checks on a class definition that has been
 /// completing, introducing implicitly-declared members, checking for
 /// abstract types, etc.

clang/lib/Sema/SemaTemplate.cpp

@@ -7379,6 +7379,13 @@ Sema::ActOnExplicitInstantiation(Scope *S,
         A->setInherited(true);
         Def->addAttr(A);
         checkClassLevelDLLAttribute(Def);
+
+        // Propagate attribute to base class templates.
+        for (auto &B : Def->bases()) {
+          if (auto *BT = dyn_cast_or_null<ClassTemplateSpecializationDecl>(
+                  B.getType()->getAsCXXRecordDecl()))
+            propagateDLLAttrToBaseClassTemplate(Def, A, BT, B.getLocStart());
+        }
       }
     }
 

clang/test/CodeGenCXX/dllexport.cpp

@@ -707,6 +707,11 @@ void PR23308::f(InternalLinkageType*) {}
 long use(PR23308* p) { p->f(nullptr); }
 // M32-DAG: define internal x86_thiscallcc void @"\01?f@PR23308@@QAEXPAUInternalLinkageType@?A@@@Z"
 
+template <typename T> struct PR23770BaseTemplate { void f() {} };
+template <typename T> struct PR23770DerivedTemplate : PR23770BaseTemplate<int> {};
+extern template struct PR23770DerivedTemplate<int>;
+template struct __declspec(dllexport) PR23770DerivedTemplate<int>;
+// M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$PR23770BaseTemplate@H@@QAEXXZ"
 
 
 //===----------------------------------------------------------------------===//

clang/test/CodeGenCXX/dllimport.cpp

@@ -741,6 +741,12 @@ USEMEMFUNC(ExplicitInstantiationDeclExportedDefImportedTemplate<int>, f);
 // M32-DAG: {{declare|define available_externally}} dllimport x86_thiscallcc void @"\01?f@?$ExplicitInstantiationDeclExportedDefImportedTemplate@H@@QAEXXZ"
 // M32-DAG: {{declare|define available_externally}} dllimport x86_thiscallcc %struct.ExplicitInstantiationDeclExportedDefImportedTemplate* @"\01??0?$ExplicitInstantiationDeclExportedDefImportedTemplate@H@@QAE@XZ"
 
+template <typename T> struct PR23770BaseTemplate { void f() {} };
+template <typename T> struct PR23770DerivedTemplate : PR23770BaseTemplate<int> {};
+extern template struct PR23770DerivedTemplate<int>;
+template struct __declspec(dllimport) PR23770DerivedTemplate<int>;
+USEMEMFUNC(PR23770BaseTemplate<int>, f);
+// M32-DAG: declare dllimport x86_thiscallcc void @"\01?f@?$PR23770BaseTemplate@H@@QAEXXZ"
 
 //===----------------------------------------------------------------------===//
 // Classes with template base classes