[analyzer] Trust summaries for OSObject::retain and OSObject::release

[george.karpenkov]

Summary

Refactor the way in which summaries are consumed for safeMetaCast

[NoQ]

clang/lib/StaticAnalyzer/Core/RetainSummaryManager.cpp

529 ↗

(On Diff #170553)

Typo: "treating". Or "testing"? (:

lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp

bool RetainCountChecker::evalCall(const CallExpr *CE, CheckerContext &C) const {
   QualType ResultTy = CE->getCallReturnType(C.getASTContext());
 
   // See if the function has 'rc_ownership_trusted_implementation'
   // annotate attribute. If it does, we will not inline it.
   bool hasTrustedImplementationAnnotation = false;
 
   const LocationContext *LCtx = C.getLocationContext();
 
-  // Process OSDynamicCast: should just return the first argument.
-  // For now, tresting the cast as a no-op, and disregarding the case where
-  // the output becomes null due to the type mismatch.
-  if (FD->getNameAsString() == "safeMetaCast") {
-    state = state->BindExpr(CE, LCtx, 
-                            state->getSVal(CE->getArg(0), LCtx));
-    C.addTransition(state);
-    return true;
-  }
-
   // See if it's one of the specific functions we know how to eval.
   if (!SmrMgr.canEval(CE, FD, hasTrustedImplementationAnnotation))
     return false;
 
   // Bind the return value.
+  // For now, all the functions which we can evaluate and which take
+  // at least one argument are identities.
+  if (CE->getNumArgs() >= 1) {
     SVal RetVal = state->getSVal(CE->getArg(0), LCtx);
-  if (RetVal.isUnknown() ||
-      (hasTrustedImplementationAnnotation && !ResultTy.isNull())) {
+
     // If the receiver is unknown or the function has
     // 'rc_ownership_trusted_implementation' annotate attribute, conjure a
     // return value.
+    if (RetVal.isUnknown() ||
+        (hasTrustedImplementationAnnotation && !ResultTy.isNull())) {
       SValBuilder &SVB = C.getSValBuilder();
-    RetVal = SVB.conjureSymbolVal(nullptr, CE, LCtx, ResultTy, C.blockCount());
+      RetVal =
+          SVB.conjureSymbolVal(nullptr, CE, LCtx, ResultTy, C.blockCount());
     }
     state = state->BindExpr(CE, LCtx, RetVal, false);
+  }
 
   C.addTransition(state);
   return true;
 }
 
 ExplodedNode * RetainCountChecker::processReturn(const ReturnStmt *S,
                                                  CheckerContext &C) const {
   ExplodedNode *Pred = C.getPredecessor();

lib/StaticAnalyzer/Core/RetainSummaryManager.cpp

 const RetainSummary *
 RetainSummaryManager::generateSummary(const FunctionDecl *FD,
                                       bool &AllowAnnotations) {
   // We generate "stop" summaries for implicitly defined functions.
   if (FD->isImplicit()) {
     return getPersistentStopSummary();
   }
 
-  // [PR 3337] Use 'getAs<FunctionType>' to strip away any typedefs on the
-  // function's type.
-  const FunctionType *FT = FD->getType()->getAs<FunctionType>();
   const IdentifierInfo *II = FD->getIdentifier();
   if (!II)
     return getDefaultSummary();
 
   StringRef FName = II->getName();
 
   // Strip away preceding '_'.  Doing this here will effect all the checks
   // down below.
   FName = FName.substr(FName.find_first_not_of('_'));
 
-  // Inspect the result type.
+  // Inspect the result type. Strip away any typedefs.
+  const auto *FT = FD->getType()->getAs<FunctionType>();
   QualType RetTy = FT->getReturnType();
   std::string RetTyName = RetTy.getAsString();
 
   // FIXME: This should all be refactored into a chain of "summary lookup"
   //  filters.
   assert(ScratchArgs.isEmpty());
 
   if (FName == "pthread_create" || FName == "pthread_setspecific") {

 bool RetainSummaryManager::isTrustedReferenceCountImplementation(
     const FunctionDecl *FD) {
   return hasRCAnnotation(FD, "rc_ownership_trusted_implementation");
 }
 
 bool RetainSummaryManager::canEval(const CallExpr *CE,
                                    const FunctionDecl *FD,
                                    bool &hasTrustedImplementationAnnotation) {
-  // For now, we're only handling the functions that return aliases of their
-  // arguments: CFRetain (and its families).
-  // Eventually we should add other functions we can model entirely,
-  // such as CFRelease, which don't invalidate their arguments or globals.
-  if (CE->getNumArgs() != 1)
-    return false;
 
   IdentifierInfo *II = FD->getIdentifier();
   if (!II)
     return false;
 
   StringRef FName = II->getName();
   FName = FName.substr(FName.find_first_not_of('_'));
 
   QualType ResultTy = CE->getCallReturnType(Ctx);
   if (ResultTy->isObjCIdType()) {
     return II->isStr("NSMakeCollectable");
   } else if (ResultTy->isPointerType()) {
     // Handle: (CF|CG|CV)Retain
     //         CFAutorelease
     // It's okay to be a little sloppy here.
     if (cocoa::isRefType(ResultTy, "CF", FName) ||
         cocoa::isRefType(ResultTy, "CG", FName) ||
         cocoa::isRefType(ResultTy, "CV", FName))
       return isRetain(FD, FName) || isAutorelease(FD, FName) ||
              isMakeCollectable(FName);
 
+    // Process OSDynamicCast: should just return the first argument.
+    // For now, treating the cast as a no-op, and disregarding the case where
+    // the output becomes null due to the type mismatch.
+    if (TrackOSObjects && FName == "safeMetaCast") {
+      return true;
+    }
+
     const FunctionDecl* FDD = FD->getDefinition();
     if (FDD && isTrustedReferenceCountImplementation(FDD)) {
       hasTrustedImplementationAnnotation = true;
       return true;
     }
   }
 
+  if (const auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
+    const CXXRecordDecl *Parent = MD->getParent();
+    if (TrackOSObjects && Parent && isOSObjectSubclass(Parent))
+      return FName == "release" || FName == "retain";
+  }
+
   return false;
 
 }
 
 const RetainSummary *
 RetainSummaryManager::getUnarySummary(const FunctionType* FT,
                                       UnaryFuncKind func) {
 

test/Analysis/osobject-retain-release.cpp

 // RUN: %clang_analyze_cc1 -analyze -analyzer-checker=core,osx.cocoa.RetainCount -analyzer-config osx.cocoa.RetainCount:CheckOSObject=true -analyzer-output=text -verify %s
 
 struct OSMetaClass;
 
 #define OSTypeID(type)   (type::metaClass)
 
 #define OSDynamicCast(type, inst)   \
     ((type *) OSMetaClassBase::safeMetaCast((inst), OSTypeID(type)))
 
 struct OSObject {
   virtual void retain();
-  virtual void release();
+  virtual void release() {};
   virtual ~OSObject(){}
 
   static OSObject *generateObject(int);
 
   static const OSMetaClass * const metaClass;
 };
 
 struct OSArray : public OSObject {