[ASTImporter] Import default expression of param before creating the param.

Summary:
The default expression of a parameter variable should be imported before
the parameter variable object is created. Otherwise the function is created
with an incomplete parameter variable (default argument is nullptr) and in
this intermediary state the expression is imported. This import can have
a reference to the incomplete parameter variable that causes crash.

Reviewers: martong, a.sidorin, shafik

Reviewed By: martong

Subscribers: rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D65577

llvm-svn: 368818

clang/include/clang/AST/ASTImporter.h

@@ -378,6 +378,20 @@ class TypeSourceInfo;
     /// imported. If it does not exist nullptr is returned.
     TranslationUnitDecl *GetFromTU(Decl *ToD);
 
+    /// Return the declaration in the "from" context from which the declaration
+    /// in the "to" context was imported. If it was not imported or of the wrong
+    /// type a null value is returned.
+    template <typename DeclT>
+    llvm::Optional<DeclT *> getImportedFromDecl(const DeclT *ToD) const {
+      auto FromI = ImportedFromDecls.find(ToD);
+      if (FromI == ImportedFromDecls.end())
+        return {};
+      auto *FromD = dyn_cast<DeclT>(FromI->second);
+      if (!FromD)
+        return {};
+      return FromD;
+    }
+
     /// Import the given declaration context from the "from"
     /// AST context into the "to" AST context.
     ///

clang/lib/AST/ASTImporter.cpp

@@ -426,6 +426,9 @@ namespace clang {
 
     Error ImportFunctionDeclBody(FunctionDecl *FromFD, FunctionDecl *ToFD);
 
+    Error ImportDefaultArgOfParmVarDecl(const ParmVarDecl *FromParam,
+                                        ParmVarDecl *ToParam);
+
     template <typename T>
     bool hasSameVisibilityContext(T *Found, T *From);
 
@@ -3841,6 +3844,28 @@ ExpectedDecl ASTNodeImporter::VisitImplicitParamDecl(ImplicitParamDecl *D) {
   return ToParm;
 }
 
+Error ASTNodeImporter::ImportDefaultArgOfParmVarDecl(
+    const ParmVarDecl *FromParam, ParmVarDecl *ToParam) {
+  ToParam->setHasInheritedDefaultArg(FromParam->hasInheritedDefaultArg());
+  ToParam->setKNRPromoted(FromParam->isKNRPromoted());
+
+  if (FromParam->hasUninstantiatedDefaultArg()) {
+    if (auto ToDefArgOrErr = import(FromParam->getUninstantiatedDefaultArg()))
+      ToParam->setUninstantiatedDefaultArg(*ToDefArgOrErr);
+    else
+      return ToDefArgOrErr.takeError();
+  } else if (FromParam->hasUnparsedDefaultArg()) {
+    ToParam->setUnparsedDefaultArg();
+  } else if (FromParam->hasDefaultArg()) {
+    if (auto ToDefArgOrErr = import(FromParam->getDefaultArg()))
+      ToParam->setDefaultArg(*ToDefArgOrErr);
+    else
+      return ToDefArgOrErr.takeError();
+  }
+
+  return Error::success();
+}
+
 ExpectedDecl ASTNodeImporter::VisitParmVarDecl(ParmVarDecl *D) {
   // Parameters are created in the translation unit's context, then moved
   // into the function declaration's context afterward.
@@ -3867,23 +3892,11 @@ ExpectedDecl ASTNodeImporter::VisitParmVarDecl(ParmVarDecl *D) {
                               /*DefaultArg*/ nullptr))
     return ToParm;
 
-  // Set the default argument.
-  ToParm->setHasInheritedDefaultArg(D->hasInheritedDefaultArg());
-  ToParm->setKNRPromoted(D->isKNRPromoted());
-
-  if (D->hasUninstantiatedDefaultArg()) {
-    if (auto ToDefArgOrErr = import(D->getUninstantiatedDefaultArg()))
-      ToParm->setUninstantiatedDefaultArg(*ToDefArgOrErr);
-    else
-      return ToDefArgOrErr.takeError();
-  } else if (D->hasUnparsedDefaultArg()) {
-    ToParm->setUnparsedDefaultArg();
-  } else if (D->hasDefaultArg()) {
-    if (auto ToDefArgOrErr = import(D->getDefaultArg()))
-      ToParm->setDefaultArg(*ToDefArgOrErr);
-    else
-      return ToDefArgOrErr.takeError();
-  }
+  // Set the default argument. It should be no problem if it was already done.
+  // Do not import the default expression before GetImportedOrCreateDecl call
+  // to avoid possible infinite import loop because circular dependency.
+  if (Error Err = ImportDefaultArgOfParmVarDecl(D, ToParm))
+    return std::move(Err);
 
   if (D->isObjCMethodParameter()) {
     ToParm->setObjCMethodScopeInfo(D->getFunctionScopeIndex());
@@ -6939,8 +6952,23 @@ ExpectedStmt ASTNodeImporter::VisitCXXDefaultArgExpr(CXXDefaultArgExpr *E) {
   if (!UsedContextOrErr)
     return UsedContextOrErr.takeError();
 
-  return CXXDefaultArgExpr::Create(
-      Importer.getToContext(), *ToUsedLocOrErr, *ToParamOrErr, *UsedContextOrErr);
+  // Import the default arg if it was not imported yet.
+  // This is needed because it can happen that during the import of the
+  // default expression (from VisitParmVarDecl) the same ParmVarDecl is
+  // encountered here. The default argument for a ParmVarDecl is set in the
+  // ParmVarDecl only after it is imported (set in VisitParmVarDecl if not here,
+  // see VisitParmVarDecl).
+  ParmVarDecl *ToParam = *ToParamOrErr;
+  if (!ToParam->getDefaultArg()) {
+    Optional<ParmVarDecl *> FromParam = Importer.getImportedFromDecl(ToParam);
+    assert(FromParam && "ParmVarDecl was not imported?");
+
+    if (Error Err = ImportDefaultArgOfParmVarDecl(*FromParam, ToParam))
+      return std::move(Err);
+  }
+
+  return CXXDefaultArgExpr::Create(Importer.getToContext(), *ToUsedLocOrErr,
+                                   *ToParamOrErr, *UsedContextOrErr);
 }
 
 ExpectedStmt

clang/test/Analysis/Inputs/ctu-other.cpp

@@ -145,3 +145,22 @@ public:
   static const int Test;
 };
 const int TestAnonUnionUSR::Test = 5;
+
+struct DefaultParmContext {
+  static const int I;
+  int f();
+};
+
+int fDefaultParm(int I = DefaultParmContext::I) {
+  return I;
+}
+
+int testImportOfIncompleteDefaultParmDuringImport(int I) {
+  return fDefaultParm(I);
+}
+
+const int DefaultParmContext::I = 0;
+
+int DefaultParmContext::f() {
+  return fDefaultParm();
+}

clang/test/Analysis/Inputs/ctu-other.cpp.externalDefMap.txt

@@ -26,3 +26,4 @@ c:@extSubSCN ctu-other.cpp.ast
 c:@extSCC ctu-other.cpp.ast
 c:@extU ctu-other.cpp.ast
 c:@S@TestAnonUnionUSR@Test ctu-other.cpp.ast
+c:@F@testImportOfIncompleteDefaultParmDuringImport#I# ctu-other.cpp.ast

clang/test/Analysis/ctu-main.cpp

@@ -125,6 +125,8 @@ public:
   static const int Test;
 };
 
+extern int testImportOfIncompleteDefaultParmDuringImport(int);
+
 int main() {
   clang_analyzer_eval(f(3) == 2); // expected-warning{{TRUE}}
   clang_analyzer_eval(f(4) == 3); // expected-warning{{TRUE}}
@@ -157,5 +159,8 @@ int main() {
   clang_analyzer_eval(extSubSCN.a == 1); // expected-warning{{TRUE}}
   // clang_analyzer_eval(extSCC.a == 7); // TODO
   clang_analyzer_eval(extU.a == 4); // expected-warning{{TRUE}}
+
   clang_analyzer_eval(TestAnonUnionUSR::Test == 5); // expected-warning{{TRUE}}
+
+  clang_analyzer_eval(testImportOfIncompleteDefaultParmDuringImport(9) == 9); // expected-warning{{TRUE}}
 }