commit bb1983cf3a1b7ff57d6cfdc05a04128bfa3721d1
author Hans Wennborg <hans@hanshq.net> Tue Jun 09 00:39:03 2015 +0000
committer Hans Wennborg <hans@hanshq.net> Tue Jun 09 00:39:03 2015 +0000
tree 1959f912066e95ccb39cb246bf9976678c3f6030
parent 29b7a939350ed4fb577545c56d54e23b06bce6d9

Enable propagation of dll attributes to previously instantiated base class templates in some cases

It is safe to add a dll attribute if the base class template previously only had
an explicit instantiation declaration, or was implicitly instantiated.

I both those cases, the members would not have been codegenned yet. In the case
of explicit instantiation declaration this is natural, and for implicit
instantiations, codegen is deferred (see r225570).

This is work towards fixing PR23770.

llvm-svn: 239373

clang/lib/Sema/SemaDeclCXX.cpp

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index b67dfb8..8859cc1 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -1356,11 +1356,23 @@
     return;
   }
 
-  if (BaseTemplateSpec->getSpecializationKind() == TSK_Undeclared) {
-    // If the base class is not already specialized, we can do the propagation.
+  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;
   }
 
@@ -4783,8 +4795,9 @@
 
   TemplateSpecializationKind TSK = Class->getTemplateSpecializationKind();
 
-  // Don't dllexport explicit class template instantiation declarations.
-  if (ClassExported && TSK == TSK_ExplicitInstantiationDeclaration) {
+  // Ignore explicit dllexport on explicit class template instantiation declarations.
+  if (ClassExported && !ClassAttr->isInherited() &&
+      TSK == TSK_ExplicitInstantiationDeclaration) {
     Class->dropAttr<DLLExportAttr>();
     return;
   }
@@ -4832,12 +4845,15 @@
     }
 
     if (MD && ClassExported) {
+      if (TSK == TSK_ExplicitInstantiationDeclaration)
+        // Don't go any further if this is just an explicit instantiation
+        // declaration.
+        continue;
+
       if (MD->isUserProvided()) {
         // Instantiate non-default class member functions ...
 
         // .. except for certain kinds of template specializations.
-        if (TSK == TSK_ExplicitInstantiationDeclaration)
-          continue;
         if (TSK == TSK_ImplicitInstantiation && !ClassAttr->isInherited())
           continue;