Don't assert on different DLL attributes in template and explicit instantiation (PR20137)

We would previously assert (a decl cannot have two DLL attributes) on this code:

  template <typename T> struct __declspec(dllimport) S { T f() { return T(); } };
  template struct __declspec(dllexport) S<int>;

The problem was that when instantiating, we would take the attribute from the
template even if the instantiation itself already had an attribute.

Also, don't inherit DLL attributes from the template to its members before
instantiation, as the attribute may change.

I couldn't figure out what MinGW does here, so I'm leaving that open. At least
we're not asserting anymore.

llvm-svn: 216340

1 files changed, 23 insertions, 11 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 5e789fe20ed..6a48162502c 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -4437,6 +4437,28 @@ static void checkDLLAttribute(Sema &S, CXXRecordDecl *Class) {
   if (!ClassAttr)
     return;
 
+  if (S.Context.getTargetInfo().getCXXABI().isMicrosoft() &&
+      !ClassAttr->isInherited()) {
+    // Diagnose dll attributes on members of class with dll attribute.
+    for (Decl *Member : Class->decls()) {
+      if (!isa<VarDecl>(Member) && !isa<CXXMethodDecl>(Member))
+        continue;
+      InheritableAttr *MemberAttr = getDLLAttr(Member);
+      if (!MemberAttr || MemberAttr->isInherited() || Member->isInvalidDecl())
+        continue;
+
+      S.Diag(MemberAttr->getLocation(),
+             diag::err_attribute_dll_member_of_dll_class)
+          << MemberAttr << ClassAttr;
+      S.Diag(ClassAttr->getLocation(), diag::note_previous_attribute);
+      Member->setInvalidDecl();
+    }
+  }
+
+  if (Class->getDescribedClassTemplate())
+    // Don't inherit dll attribute until the template is instantiated.
+    return;
+
   bool ClassExported = ClassAttr->getKind() == attr::DLLExport;
 
   // Force declaration of implicit members so they can inherit the attribute.
@@ -4467,17 +4489,7 @@ static void checkDLLAttribute(Sema &S, CXXRecordDecl *Class) {
       continue;
     }
 
-    if (InheritableAttr *MemberAttr = getDLLAttr(Member)) {
-      if (S.Context.getTargetInfo().getCXXABI().isMicrosoft() &&
-          !MemberAttr->isInherited() && !ClassAttr->isInherited()) {
-        S.Diag(MemberAttr->getLocation(),
-               diag::err_attribute_dll_member_of_dll_class)
-            << MemberAttr << ClassAttr;
-        S.Diag(ClassAttr->getLocation(), diag::note_previous_attribute);
-        Member->setInvalidDecl();
-        continue;
-      }
-    } else {
+    if (!getDLLAttr(Member)) {
       auto *NewAttr =
           cast<InheritableAttr>(ClassAttr->clone(S.getASTContext()));
       NewAttr->setInherited(true);