[analyzer] NFC: RetainCount: Don't dump() regions to the user.

[NoQ]

Summary

RetainCountChecker appears to be using MemRegion::getString() to present the region to the user, which is equivalent to MemRegion->dump() and as such may produce human-unreadable dumps.

Fortunately, for now RetainCountChecker only tracks pointer bindings through local variables, and treats all other bindings as pointer escapes. For local variables, this worked well.

Before r315736/D38877, however, it used to be possible to modify retain count of a pointer "in place" after writing it anywhere, eg.:

anyWeirdLocation = x;
SafeCFRetain(anyWeirdLocation);

...which not only caused a leak false positive, but also triggered a dump of anyWeirdLocation (which may be literally any weird location) into the checker's warning message.

So for now i'm not seeing any other cases where this leaks, but i still want to add an assertion to make sure this never happens again.

[dcoughlin]

LGTM. Thanks for fixing this.

lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp

static bool isNumericLiteralExpression(const Expr *E) {
   // FIXME: This set of cases was copied from SemaExprObjC.
   return isa<IntegerLiteral>(E) ||
          isa<CharacterLiteral>(E) ||
          isa<FloatingLiteral>(E) ||
          isa<ObjCBoolLiteralExpr>(E) ||
          isa<CXXBoolLiteralExpr>(E);
 }
 
+static std::string describeRegion(const MemRegion *MR) {
+  // Once we support more storage locations for bindings,
+  // this would need to be improved.
+  return cast<VarRegion>(MR)->getDecl()->getName();
+}
+
 /// Returns true if this stack frame is for an Objective-C method that is a
 /// property getter or setter whose body has been synthesized by the analyzer.
 static bool isSynthesizedAccessor(const StackFrameContext *SFC) {
   auto Method = dyn_cast_or_null<ObjCMethodDecl>(SFC->getDecl());
   if (!Method || !Method->isPropertyAccessor())
     return false;
 
   return SFC->getAnalysisDeclContext()->isBodyAutosynthesized();
CFRefLeakReportVisitor::getEndPath(BugReporterContext &BRC,
 
   std::string sbuf;
   llvm::raw_string_ostream os(sbuf);
 
   os << "Object leaked: ";
 
   if (FirstBinding) {
     os << "object allocated and stored into '"
-       << FirstBinding->getString() << '\'';
+       << describeRegion(FirstBinding) << '\'';
   }
   else
     os << "allocated object";
 
   // Get the retain count.
   const RefVal* RV = getRefBinding(EndN->getState(), Sym);
   assert(RV);
 
void CFRefLeakReport::createDescription(CheckerContext &Ctx, bool GCEnabled, bool IncludeAllocationLine) {
   Description.clear();
   llvm::raw_string_ostream os(Description);
   os << "Potential leak ";
   if (GCEnabled)
     os << "(when using garbage collection) ";
   os << "of an object";
 
   if (AllocBinding) {
-    os << " stored into '" << AllocBinding->getString() << '\'';
+    os << " stored into '" << describeRegion(AllocBinding) << '\'';
     if (IncludeAllocationLine) {
       FullSourceLoc SL(AllocStmt->getLocStart(), Ctx.getSourceManager());
       os << " (allocated on line " << SL.getSpellingLineNumber() << ")";
     }
   }
 }
 
 CFRefLeakReport::CFRefLeakReport(CFRefBug &D, const LangOptions &LOpts,