commit b792e0694b678e08832d5cfcb52d800c6f1a01aa
author Reid Kleckner <rnk@google.com> Tue Dec 06 21:44:41 2016 +0000
committer Reid Kleckner <rnk@google.com> Tue Dec 06 21:44:41 2016 +0000
tree 1eb0ef046e6b1006d07a41e632201628ab208322
parent 00cfa747156c8a7bb25be3e6a85272a61b0b15ca

Disable -Wweak-vtables when there are no key functions

Our -Wweak-vtables diagnostic is powered by our key function
calculation, which checks if key functions are enabled. We won't find
any key functions in C++ ABIs that lack key functions, so -Wweak-vtables
was warning on every dynamic class before this change. So, turn off this
warning in ABIs without key functions.

Addresses PR31220

llvm-svn: 288850

clang/lib/Sema/SemaDeclCXX.cpp

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 6ccb3c5..ed77a42 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -14281,6 +14281,8 @@
     CXXRecordDecl *Class = VTableUses[I].first->getDefinition();
     if (!Class)
       continue;
+    TemplateSpecializationKind ClassTSK =
+        Class->getTemplateSpecializationKind();
 
     SourceLocation Loc = VTableUses[I].second;
 
@@ -14304,9 +14306,8 @@
       // of an explicit instantiation declaration, suppress the
       // vtable; it will live with the explicit instantiation
       // definition.
-      bool IsExplicitInstantiationDeclaration
-        = Class->getTemplateSpecializationKind()
-                                      == TSK_ExplicitInstantiationDeclaration;
+      bool IsExplicitInstantiationDeclaration =
+          ClassTSK == TSK_ExplicitInstantiationDeclaration;
       for (auto R : Class->redecls()) {
         TemplateSpecializationKind TSK
           = cast<CXXRecordDecl>(R)->getTemplateSpecializationKind();
@@ -14339,17 +14340,20 @@
     if (VTablesUsed[Canonical])
       Consumer.HandleVTable(Class);
 
-    // Optionally warn if we're emitting a weak vtable.
-    if (Class->isExternallyVisible() &&
-        Class->getTemplateSpecializationKind() != TSK_ImplicitInstantiation) {
+    // Warn if we're emitting a weak vtable. The vtable will be weak if there is
+    // no key function or the key function is inlined. Don't warn in C++ ABIs
+    // that lack key functions, since the user won't be able to make one.
+    if (Context.getTargetInfo().getCXXABI().hasKeyFunctions() &&
+        Class->isExternallyVisible() && ClassTSK != TSK_ImplicitInstantiation) {
       const FunctionDecl *KeyFunctionDef = nullptr;
-      if (!KeyFunction || 
-          (KeyFunction->hasBody(KeyFunctionDef) && 
-           KeyFunctionDef->isInlined()))
-        Diag(Class->getLocation(), Class->getTemplateSpecializationKind() ==
-             TSK_ExplicitInstantiationDefinition 
-             ? diag::warn_weak_template_vtable : diag::warn_weak_vtable) 
-          << Class;
+      if (!KeyFunction || (KeyFunction->hasBody(KeyFunctionDef) &&
+                           KeyFunctionDef->isInlined())) {
+        Diag(Class->getLocation(),
+             ClassTSK == TSK_ExplicitInstantiationDefinition
+                 ? diag::warn_weak_template_vtable
+                 : diag::warn_weak_vtable)
+            << Class;
+      }
     }
   }
   VTableUses.clear();