C++ modules: Don't call DeclContext::lookup when half-way through deserializing

decls. That can reenter deserialization and explode horribly by trying to merge
a declaration that we've not got very far through deserializing yet.

llvm-svn: 186236

clang/include/clang/AST/DeclBase.h

@@ -991,6 +991,7 @@ protected:
   mutable Decl *LastDecl;
 
   friend class ExternalASTSource;
+  friend class ASTDeclReader;
   friend class ASTWriter;
 
   /// \brief Build up a chain of declarations.
@@ -1446,12 +1447,20 @@ public:
     return const_cast<DeclContext*>(this)->lookup(Name);
   }
 
+  /// \brief Find the declarations with the given name that are visible
+  /// within this context; don't attempt to retrieve anything from an
+  /// external source.
+  lookup_result noload_lookup(DeclarationName Name);
+
   /// \brief A simplistic name lookup mechanism that performs name lookup
   /// into this declaration context without consulting the external source.
   ///
   /// This function should almost never be used, because it subverts the
   /// usual relationship between a DeclContext and the external source.
   /// See the ASTImporter for the (few, but important) use cases.
+  ///
+  /// FIXME: This is very inefficient; replace uses of it with uses of
+  /// noload_lookup.
   void localUncachedLookup(DeclarationName Name,
                            SmallVectorImpl<NamedDecl *> &Results);
 
@@ -1573,6 +1582,8 @@ private:
   friend class DependentDiagnostic;
   StoredDeclsMap *CreateStoredDeclsMap(ASTContext &C) const;
 
+  template<decl_iterator (DeclContext::*Begin)() const,
+           decl_iterator (DeclContext::*End)() const>
   void buildLookupImpl(DeclContext *DCtx);
   void makeDeclVisibleInContextWithFlags(NamedDecl *D, bool Internal,
                                          bool Rediscoverable);

clang/lib/AST/DeclBase.cpp

@@ -1170,7 +1170,8 @@ StoredDeclsMap *DeclContext::buildLookup() {
   SmallVector<DeclContext *, 2> Contexts;
   collectAllContexts(Contexts);
   for (unsigned I = 0, N = Contexts.size(); I != N; ++I)
-    buildLookupImpl(Contexts[I]);
+    buildLookupImpl<&DeclContext::decls_begin,
+                    &DeclContext::decls_end>(Contexts[I]);
 
   // We no longer have any lazy decls.
   LookupPtr.setInt(false);
@@ -1182,8 +1183,10 @@ StoredDeclsMap *DeclContext::buildLookup() {
 /// declarations contained within DCtx, which will either be this
 /// DeclContext, a DeclContext linked to it, or a transparent context
 /// nested within it.
+template<DeclContext::decl_iterator (DeclContext::*Begin)() const,
+         DeclContext::decl_iterator (DeclContext::*End)() const>
 void DeclContext::buildLookupImpl(DeclContext *DCtx) {
-  for (decl_iterator I = DCtx->decls_begin(), E = DCtx->decls_end();
+  for (decl_iterator I = (DCtx->*Begin)(), E = (DCtx->*End)();
        I != E; ++I) {
     Decl *D = *I;
 
@@ -1207,7 +1210,7 @@ void DeclContext::buildLookupImpl(DeclContext *DCtx) {
     // context (recursively).
     if (DeclContext *InnerCtx = dyn_cast<DeclContext>(D))
       if (InnerCtx->isTransparentContext() || InnerCtx->isInlineNamespace())
-        buildLookupImpl(InnerCtx);
+        buildLookupImpl<Begin, End>(InnerCtx);
   }
 }
 
@@ -1264,6 +1267,45 @@ DeclContext::lookup(DeclarationName Name) {
   return I->second.getLookupResult();
 }
 
+DeclContext::lookup_result
+DeclContext::noload_lookup(DeclarationName Name) {
+  assert(DeclKind != Decl::LinkageSpec &&
+         "Should not perform lookups into linkage specs!");
+  if (!hasExternalVisibleStorage())
+    return lookup(Name);
+
+  DeclContext *PrimaryContext = getPrimaryContext();
+  if (PrimaryContext != this)
+    return PrimaryContext->noload_lookup(Name);
+
+  StoredDeclsMap *Map = LookupPtr.getPointer();
+  if (LookupPtr.getInt()) {
+    // Carefully build the lookup map, without deserializing anything.
+    SmallVector<DeclContext *, 2> Contexts;
+    collectAllContexts(Contexts);
+    for (unsigned I = 0, N = Contexts.size(); I != N; ++I)
+      buildLookupImpl<&DeclContext::noload_decls_begin,
+                      &DeclContext::noload_decls_end>(Contexts[I]);
+
+    // We no longer have any lazy decls.
+    LookupPtr.setInt(false);
+
+    // There may now be names for which we have local decls but are
+    // missing the external decls.
+    NeedToReconcileExternalVisibleStorage = true;
+
+    Map = LookupPtr.getPointer();
+  }
+
+  if (!Map)
+    return lookup_result(lookup_iterator(0), lookup_iterator(0));
+
+  StoredDeclsMap::iterator I = Map->find(Name);
+  return I != Map->end()
+             ? I->second.getLookupResult()
+             : lookup_result(lookup_iterator(0), lookup_iterator(0));
+}
+
 void DeclContext::localUncachedLookup(DeclarationName Name,
                                       SmallVectorImpl<NamedDecl *> &Results) {
   Results.clear();

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -1914,14 +1914,15 @@ static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
 ASTDeclReader::FindExistingResult::~FindExistingResult() {
   if (!AddResult || Existing)
     return;
-  
-  if (New->getDeclContext()->getRedeclContext()->isTranslationUnit()
-      && Reader.SemaObj) {
+
+  DeclContext *DC = New->getDeclContext()->getRedeclContext();
+  if (DC->isTranslationUnit() && Reader.SemaObj) {
     Reader.SemaObj->IdResolver.tryAddTopLevelDecl(New, New->getDeclName());
-  } else {
-    DeclContext *DC = New->getLexicalDeclContext();
-    if (DC->isNamespace())
-      DC->addDecl(New);
+  } else if (NamespaceDecl *NS = dyn_cast<NamespaceDecl>(DC)) {
+    // Add the declaration to its redeclaration context so later merging
+    // lookups will find it.
+    NS->getFirstDeclaration()->makeDeclVisibleInContextImpl(New,
+                                                            /*Internal*/true);
   }
 }
 
@@ -1933,11 +1934,11 @@ ASTDeclReader::FindExistingResult ASTDeclReader::findExisting(NamedDecl *D) {
     Result.suppress();
     return Result;
   }
-  
+
   DeclContext *DC = D->getDeclContext()->getRedeclContext();
   if (!DC->isFileContext())
     return FindExistingResult(Reader);
-  
+
   if (DC->isTranslationUnit() && Reader.SemaObj) {
     IdentifierResolver &IdResolver = Reader.SemaObj->IdResolver;
 
@@ -1970,12 +1971,9 @@ ASTDeclReader::FindExistingResult ASTDeclReader::findExisting(NamedDecl *D) {
       if (isSameEntity(*I, D))
         return FindExistingResult(Reader, D, *I);
     }
-  }
-
-  if (DC->isNamespace()) {
-    DeclContext::lookup_result R = DC->lookup(Name);
-    for (DeclContext::lookup_iterator I = R.begin(), E = R.end(); I != E; 
-         ++I) {
+  } else if (NamespaceDecl *NS = dyn_cast<NamespaceDecl>(DC)) {
+    DeclContext::lookup_result R = NS->getFirstDeclaration()->noload_lookup(Name);
+    for (DeclContext::lookup_iterator I = R.begin(), E = R.end(); I != E; ++I) {
       if (isSameEntity(*I, D))
         return FindExistingResult(Reader, D, *I);
     }

clang/test/PCH/cxx-templates.cpp

@@ -94,3 +94,8 @@ namespace rdar13135282 {
 void CallDependentSpecializedFunc(DependentSpecializedFuncClass<int> &x) {
   DependentSpecializedFunc(x);
 }
+
+namespace cyclic_module_load {
+  extern std::valarray<int> x;
+  std::valarray<int> y(x);
+}

clang/test/PCH/cxx-templates.h

@@ -276,3 +276,23 @@ template<typename T> class DependentSpecializedFuncClass {
   void foo() {}
   friend void DependentSpecializedFunc<>(DependentSpecializedFuncClass);
 };
+
+namespace cyclic_module_load {
+  // Reduced from a libc++ modules crasher.
+  namespace std {
+    template<class> class mask_array;
+    template<class> class valarray {
+    public:
+      valarray(const valarray &v);
+    };
+
+    class gslice {
+      valarray<int> x;
+      valarray<int> stride() const { return x; }
+    };
+
+    template<class> class mask_array {
+      template<class> friend class valarray;
+    };
+  }
+}