[analyzer] Fix crashes in RetainCountChecker when underlying region is not a var

[george.karpenkov]

Summary

For other regions, the error message contains a good indication of the problem, and there, in general, nothing helpful we can print.
Error pointer to the problematic expression seems enough.

[dcoughlin]

Looks good. It is nice to see this fixed. There is one testing nit inline

test/Analysis/retaincountchecker-compoundregion.m

22

Can you use // expected-warning-re{{Potential leak of an object$}} here? This will make sure that the diagnostic doesn't include any extra text after 'object'.

lib/StaticAnalyzer/Checkers/RetainCountChecker.cpp

   // 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) {
+static Optional<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();
+  if (const auto *VR = dyn_cast<VarRegion>(MR)) {
+    std::string Out = cast<VarRegion>(MR)->getDecl()->getName();
+    return Out;
+  }
+  return None;
 }
 
 /// 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;

   const ExplodedNode *LeakN = EndN;
   PathDiagnosticLocation L = PathDiagnosticLocation::createEndOfPath(LeakN, SM);
 
   std::string sbuf;
   llvm::raw_string_ostream os(sbuf);
 
   os << "Object leaked: ";
 
-  if (FirstBinding) {
-    os << "object allocated and stored into '"
-       << describeRegion(FirstBinding) << '\'';
+  Optional<std::string> RegionDescription = describeRegion(FirstBinding);
+  if (FirstBinding && RegionDescription) {
+    os << "object allocated and stored into '" << *RegionDescription << '\'';
   }
   else
     os << "allocated object";
 
   // Get the retain count.
   const RefVal* RV = getRefBinding(EndN->getState(), Sym);
   assert(RV);
 

   Location = AllocLocation;
 
   // Set uniqieing info, which will be used for unique the bug reports. The
   // leaks should be uniqued on the allocation site.
   UniqueingLocation = AllocLocation;
   UniqueingDecl = AllocNode->getLocationContext()->getDecl();
 }
 
-void CFRefLeakReport::createDescription(CheckerContext &Ctx, bool GCEnabled, bool IncludeAllocationLine) {
+void CFRefLeakReport::createDescription(CheckerContext &Ctx, bool GCEnabled,
+                                        bool IncludeAllocationLine) {
   assert(Location.isValid() && UniqueingDecl && UniqueingLocation.isValid());
   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 '" << describeRegion(AllocBinding) << '\'';
+  Optional<std::string> RegionDescription = describeRegion(AllocBinding);
+  if (AllocBinding && RegionDescription) {
+    os << " stored into '" << *RegionDescription << '\'';
     if (IncludeAllocationLine) {
       FullSourceLoc SL(AllocStmt->getLocStart(), Ctx.getSourceManager());
       os << " (allocated on line " << SL.getSpellingLineNumber() << ")";
     }
   }
 }
 
 CFRefLeakReport::CFRefLeakReport(CFRefBug &D, const LangOptions &LOpts,

test/Analysis/retaincountchecker-compoundregion.m

+// RUN: %clang_analyze_cc1 -analyzer-checker=core,osx -fblocks -verify -Wno-objc-root-class %s
+typedef const void *CFTypeRef;
+enum { kCFNumberSInt8Type = 1, kCFNumberSInt16Type = 2,
+       kCFNumberSInt32Type = 3, kCFNumberSInt64Type = 4,
+       kCFNumberFloat32Type = 5, kCFNumberFloat64Type = 6,
+       kCFNumberCharType = 7, kCFNumberShortType = 8,
+       kCFNumberIntType = 9, kCFNumberLongType = 10,
+       kCFNumberLongLongType = 11, kCFNumberFloatType = 12,
+       kCFNumberDoubleType = 13, kCFNumberCFIndexType = 14,
+       kCFNumberNSIntegerType = 15, kCFNumberCGFloatType = 16,
+       kCFNumberMaxType = 16 };
+typedef const struct __CFAllocator * CFAllocatorRef;
+typedef signed long CFIndex;
+typedef CFIndex CFNumberType;
+typedef const struct __CFNumber * CFNumberRef;
+extern CFNumberRef CFNumberCreate(CFAllocatorRef allocator, CFNumberType theType, const void *valuePtr);
+
+void foo(CFAllocatorRef allocator) {
+  int width = 0;
+  int height = 0;
+  CFTypeRef* values = (CFTypeRef[]){
+    CFNumberCreate(allocator, kCFNumberSInt32Type, &width), //expected-warning{{Potential leak of an object}}
+    CFNumberCreate(allocator, kCFNumberSInt32Type, &height), //expected-warning{{Potential leak of an object}}
+  };
+}