Stop tracking retain count of OSObject after escape to void * / other primitive types

[george.karpenkov]

Summary

Escaping to void * / uint64_t / others non-OSObject * should stop tracking,
as such functions can have heterogeneous semantics depending on context, and can not always be annotated.

rdar://46439133

[NoQ]

Sounds reasonable.

lib/StaticAnalyzer/Checkers/RetainCountChecker/RetainCountChecker.cpp

static ProgramStateRef updateOutParameter(ProgramStateRef State,
 
   default:
     llvm_unreachable("only for out parameters");
   }
 
   return State;
 }
 
+static bool isPointerToObject(QualType QT) {
+  QualType PT = QT->getPointeeType();
+  if (!PT.isNull())
+    if (PT->getAsCXXRecordDecl())
+      return true;
+  return false;
+}
+
+/// Whether the tracked value should be escaped on a given call.
+/// OSObjects are escaped when passed to void * / etc.
+static bool shouldEscapeArgumentOnCall(const CallEvent &CE, unsigned ArgIdx,
+                                       const RefVal *TrackedValue) {
+  if (TrackedValue->getObjKind() != RetEffect::OS)
+    return false;
+  if (ArgIdx >= CE.parameters().size())
+    return false;
+  return !isPointerToObject(CE.parameters()[ArgIdx]->getType());
+}
+
 void RetainCountChecker::checkSummary(const RetainSummary &Summ,
                                       const CallEvent &CallOrMsg,
                                       CheckerContext &C) const {
   ProgramStateRef state = C.getState();
 
   // Evaluate the effect of the arguments.
   RefVal::Kind hasErr = (RefVal::Kind) 0;
   SourceRange ErrorRange;
   SymbolRef ErrorSym = nullptr;
 
   for (unsigned idx = 0, e = CallOrMsg.getNumArgs(); idx != e; ++idx) {
     SVal V = CallOrMsg.getArgSVal(idx);
 
     ArgEffect Effect = Summ.getArg(idx);
     if (Effect == RetainedOutParameter || Effect == UnretainedOutParameter) {
       state = updateOutParameter(state, V, Effect);
     } else if (SymbolRef Sym = V.getAsLocSymbol()) {
       if (const RefVal *T = getRefBinding(state, Sym)) {
+
+        if (shouldEscapeArgumentOnCall(CallOrMsg, idx, T))
+          Effect = StopTrackingHard;
+
         state = updateSymbol(state, Sym, *T, Effect, hasErr, C);
         if (hasErr) {
           ErrorRange = CallOrMsg.getArgSourceRange(idx);
           ErrorSym = Sym;
           break;
         }
       }
     }

test/Analysis/osobject-retain-release.cpp

struct OtherStruct {
   static void doNothingToArray(OSArray *array);
   OtherStruct(OSArray *arr);
 };
 
 struct OSMetaClassBase {
   static OSObject *safeMetaCast(const OSObject *inst, const OSMetaClass *meta);
 };
 
+void escape(void *);
+
+void test_escaping_into_voidstar() {
+  OSObject *obj = new OSObject;
+  escape(obj);
+}
+
 void test_no_infinite_check_recursion(MyArray *arr) {
   OSObject *input = new OSObject;
   OSObject *o = arr->generateObject(input);
   o->release();
   input->release();
 }