For dllexport class templates, export specializations of member functions (PR34849) (take 2)

This is a re-commit of r315025, but making sure to only apply this to
specializations of class template member functions; i.e. not when the function
itself is a template.

llvm-svn: 315330

clang/lib/Sema/SemaDecl.cpp

@@ -6041,6 +6041,22 @@ static void checkDLLAttributeRedeclaration(Sema &S, NamedDecl *OldDecl,
            diag::warn_dllimport_dropped_from_inline_function)
         << NewDecl << OldImportAttr;
   }
+
+  // A specialization of a class template member function is processed here
+  // since it's a redeclaration. If the parent class is dllexport, the
+  // specialization inherits that attribute. This doesn't happen automatically
+  // since the parent class isn't instantiated until later.
+  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewDecl)) {
+    if (MD->getTemplatedKind() == FunctionDecl::TK_MemberSpecialization &&
+        !NewImportAttr && !NewExportAttr) {
+      if (const DLLExportAttr *ParentExportAttr =
+              MD->getParent()->getAttr<DLLExportAttr>()) {
+        DLLExportAttr *NewAttr = ParentExportAttr->clone(S.Context);
+        NewAttr->setInherited(true);
+        NewDecl->addAttr(NewAttr);
+      }
+    }
+  }
 }
 
 /// Given that we are within the definition of the given function,

clang/test/CodeGenCXX/dllexport.cpp

@@ -831,6 +831,21 @@ template <typename T> struct ExplicitInstantiationTwoAttributes { void f() {} };
 template struct __declspec(dllexport) __declspec(dllimport) ExplicitInstantiationTwoAttributes<int>;
 // M32-DAG: define weak_odr dllexport x86_thiscallcc void @"\01?f@?$ExplicitInstantiationTwoAttributes@H@@QAEXXZ"
 
+namespace pr34849 {
+// Specializations of exported class template member functions get exported.
+template <typename> struct __declspec(dllexport) ExportedClassTemplate { void foo(); };
+template<> void ExportedClassTemplate<int>::foo() {}
+template struct ExportedClassTemplate<int>;
+// M32-DAG: define dllexport x86_thiscallcc void @"\01?foo@?$ExportedClassTemplate@H@pr34849@@QAEXXZ"
+
+// Specializations of exported class member template functions do not get exported.
+struct __declspec(dllexport) ExportedClass { template <typename> void bar() ; };
+template<> void ExportedClass::bar<int>() {}
+// M32-DAG: define x86_thiscallcc void @"\01??$bar@H@ExportedClass@pr34849@@QAEXXZ"
+template <typename> struct __declspec(dllexport) ExportedClassTemplate2 { template <typename> void baz(); };
+template<> template<> void ExportedClassTemplate2<int>::baz<int>() {}
+// M32-DAG: define x86_thiscallcc void @"\01??$baz@H@?$ExportedClassTemplate2@H@pr34849@@QAEXXZ"
+}
 
 //===----------------------------------------------------------------------===//
 // Classes with template base classes