Don't propagate dllimport to base class template static data members

MSVC doesn't, so we shouldn't. Fixes PR37232.

llvm-svn: 332074

clang/include/clang/Basic/Attr.td

@@ -2566,6 +2566,16 @@ def DLLImport : InheritableAttr, TargetSpecificAttr<TargetWindows> {
   let Spellings = [Declspec<"dllimport">, GCC<"dllimport">];
   let Subjects = SubjectList<[Function, Var, CXXRecord, ObjCInterface]>;
   let Documentation = [DLLImportDocs];
+
+
+  let AdditionalMembers = [{
+private:
+  bool PropagatedToBaseTemplate = false;
+
+public:
+  void setPropagatedToBaseTemplate() { PropagatedToBaseTemplate = true; }
+  bool wasPropagatedToBaseTemplate() { return PropagatedToBaseTemplate; }
+  }];
 }
 
 def SelectAny : InheritableAttr {

clang/lib/Sema/SemaDeclCXX.cpp

@@ -5626,6 +5626,13 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
   // The class is either imported or exported.
   const bool ClassExported = ClassAttr->getKind() == attr::DLLExport;
 
+  // Check if this was a dllimport attribute propagated from a derived class to
+  // a base class template specialization. We don't apply these attributes to
+  // static data members.
+  const bool PropagatedImport =
+      !ClassExported &&
+      cast<DLLImportAttr>(ClassAttr)->wasPropagatedToBaseTemplate();
+
   TemplateSpecializationKind TSK = Class->getTemplateSpecializationKind();
 
   // Ignore explicit dllexport on explicit class template instantiation declarations.
@@ -5677,6 +5684,11 @@ void Sema::checkClassLevelDLLAttribute(CXXRecordDecl *Class) {
       }
     }
 
+    // Don't apply dllimport attributes to static data members of class template
+    // instantiations when the attribute is propagated from a derived class.
+    if (VD && PropagatedImport)
+      continue;
+
     if (!cast<NamedDecl>(Member)->isExternallyVisible())
       continue;
 
@@ -5729,6 +5741,11 @@ void Sema::propagateDLLAttrToBaseClassTemplate(
     NewAttr->setInherited(true);
     BaseTemplateSpec->addAttr(NewAttr);
 
+    // If this was an import, mark that we propagated it from a derived class to
+    // a base class template specialization.
+    if (auto *ImportAttr = dyn_cast<DLLImportAttr>(NewAttr))
+      ImportAttr->setPropagatedToBaseTemplate();
+
     // 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.

clang/test/CodeGenCXX/dllimport-template-sdm.cpp

@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++14 -fms-extensions -o - %s | FileCheck %s --check-prefix=IMPORT
+// RUN: %clang_cc1 -triple x86_64-windows-msvc -emit-llvm -std=c++14 -fms-extensions -o - %s -DTEST_EXPORT | FileCheck %s --check-prefix=EXPORT
+
+#ifndef TEST_EXPORT
+#define DLLATTR __declspec(dllimport)
+#else
+#define DLLATTR __declspec(dllexport)
+#endif
+
+// PR37232: When a dllimport attribute is propagated from a derived class to a
+// base class that happens to be a template specialization, it is only applied
+// to template *methods*, and not static data members. If a dllexport attribute
+// is propagated, it still applies to static data members.
+
+// IMPORT-DAG: @"?sdm@Exporter@@2HB" = available_externally dllimport constant i32 2, align 4
+// IMPORT-DAG: @"?csdm@?$A@H@@2HB" = linkonce_odr dso_local constant i32 2, comdat, align 4
+// IMPORT-DAG: @"?sdm@?$A@H@@2HA" = linkonce_odr dso_local global i32 1, comdat, align 4
+// IMPORT-DAG: @"?sdm@?$B@H@@2HB" = available_externally dllimport constant i32 2, align 4
+// IMPORT-DAG: @"?sdm@?$C@H@@2HB" = available_externally dllimport constant i32 2, align 4
+
+// EXPORT-DAG: @"?sdm@Exporter@@2HB" = weak_odr dso_local dllexport constant i32 2, comdat, align 4
+// EXPORT-DAG: @"?csdm@?$A@H@@2HB" = weak_odr dso_local dllexport constant i32 2, comdat, align 4
+// EXPORT-DAG: @"?sdm@?$A@H@@2HA" = weak_odr dso_local dllexport global i32 1, comdat, align 4
+// EXPORT-DAG: @"?sdm@?$B@H@@2HB" = weak_odr dso_local dllexport constant i32 2, comdat, align 4
+// EXPORT-DAG: @"?sdm@?$C@H@@2HB" = weak_odr dso_local dllexport constant i32 2, comdat, align 4
+
+
+template <typename T> struct A {
+  static constexpr int csdm = 2;
+  static int sdm;
+};
+template <typename T> int A<T>::sdm = 1;
+
+struct DLLATTR Exporter : A<int> {
+  static constexpr int sdm = 2;
+};
+
+template <typename T> struct DLLATTR B { static constexpr int sdm = 2; };
+
+template <typename T> struct DLLATTR C;
+template <typename T> struct C { static constexpr int sdm = 2; };
+
+void takeRef(const int &_Args) {}
+
+int main() {
+  takeRef(Exporter::sdm);
+  takeRef(A<int>::csdm);
+  takeRef(A<int>::sdm);
+  takeRef(B<int>::sdm);
+  takeRef(C<int>::sdm);
+
+  return 1;
+}