C++ modules: fix a bug where loading a declaration with some name would prevent

name lookup from lazily deserializing the other declarations with the same
name, by tracking a bit to indicate whether a name in a DeclContext might have
additional external results. This also allows lazier reconciling of the lookup
table if a module import adds decls to a pre-existing DC.

However, this exposes a pre-existing bug, which causes a regression in
test/Modules/decldef.mm: if we have a reference to a declaration, and a
later-imported module adds a redeclaration, nothing causes us to load that
redeclaration when we use or emit the reference (which can manifest as a
reference to an undefined inline function, a use of an incomplete type, and so
on). decldef.mm has been extended with an additional testcase which fails with
or without this change.

llvm-svn: 190293

1 files changed, 20 insertions, 14 deletions

diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index e4d4e77942d..be1992a4d54 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -926,11 +926,8 @@ void DeclContext::reconcileExternalVisibleStorage() {
   NeedToReconcileExternalVisibleStorage = false;
 
   StoredDeclsMap &Map = *LookupPtr.getPointer();
-  ExternalASTSource *Source = getParentASTContext().getExternalSource();
-  for (StoredDeclsMap::iterator I = Map.begin(); I != Map.end(); ++I) {
-    I->second.removeExternalDecls();
-    Source->FindExternalVisibleDeclsByName(this, I->first);
-  }
+  for (StoredDeclsMap::iterator I = Map.begin(); I != Map.end(); ++I)
+    I->second.setHasExternalDecls();
 }
 
 /// \brief Load the declarations within this lexical storage from an
@@ -983,8 +980,7 @@ ExternalASTSource::SetNoExternalVisibleDeclsForName(const DeclContext *DC,
   if (!(Map = DC->LookupPtr.getPointer()))
     Map = DC->CreateStoredDeclsMap(Context);
 
-  // Add an entry to the map for this name, if it's not already present.
-  (*Map)[Name];
+  (*Map)[Name].removeExternalDecls();
 
   return DeclContext::lookup_result();
 }
@@ -1246,16 +1242,14 @@ DeclContext::lookup(DeclarationName Name) {
     if (!Map)
       Map = CreateStoredDeclsMap(getParentASTContext());
 
-    // If a PCH/module has a result for this name, and we have a local
-    // declaration, we will have imported the PCH/module result when adding the
-    // local declaration or when reconciling the module.
+    // If we have a lookup result with no external decls, we are done.
     std::pair<StoredDeclsMap::iterator, bool> R =
         Map->insert(std::make_pair(Name, StoredDeclsList()));
-    if (!R.second)
+    if (!R.second && !R.first->second.hasExternalDecls())
       return R.first->second.getLookupResult();
 
     ExternalASTSource *Source = getParentASTContext().getExternalSource();
-    if (Source->FindExternalVisibleDeclsByName(this, Name)) {
+    if (Source->FindExternalVisibleDeclsByName(this, Name) || R.second) {
       if (StoredDeclsMap *Map = LookupPtr.getPointer()) {
         StoredDeclsMap::iterator I = Map->find(Name);
         if (I != Map->end())
@@ -1304,7 +1298,8 @@ DeclContext::noload_lookup(DeclarationName Name) {
     LookupPtr.setInt(false);
 
     // There may now be names for which we have local decls but are
-    // missing the external decls.
+    // missing the external decls. FIXME: Just set the hasExternalDecls
+    // flag on those names that have external decls.
     NeedToReconcileExternalVisibleStorage = true;
 
     Map = LookupPtr.getPointer();
@@ -1461,7 +1456,18 @@ void DeclContext::makeDeclVisibleInContextImpl(NamedDecl *D, bool Internal) {
 
   // Insert this declaration into the map.
   StoredDeclsList &DeclNameEntries = (*Map)[D->getDeclName()];
-  if (DeclNameEntries.isNull()) {
+
+  if (Internal) {
+    // If this is being added as part of loading an external declaration,
+    // this may not be the only external declaration with this name.
+    // In this case, we never try to replace an existing declaration; we'll
+    // handle that when we finalize the list of declarations for this name.
+    DeclNameEntries.setHasExternalDecls();
+    DeclNameEntries.AddSubsequentDecl(D);
+    return;
+  }
+
+  else if (DeclNameEntries.isNull()) {
     DeclNameEntries.setOnlyValue(D);
     return;
   }