[PATCH] [Static Analyzer] Remove ObjCContainersChecker size information when a CFMutableArrayRef escapes

[Devin Coughlin]

Hi zaks.anna, jordan_rose,

Update ObjCContainersChecker to be notified when pointers escape so it can remove size information for escaping CFMutableArrayRefs. When such pointers escape, un-analyzed code could mutate the array and cause the size information to be incorrect.

rdar://problem/19406485

http://reviews.llvm.org/D10225

Files:
  lib/StaticAnalyzer/Checkers/ObjCContainersChecker.cpp
  test/Analysis/CFContainers.mm

Index: lib/StaticAnalyzer/Checkers/ObjCContainersChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/ObjCContainersChecker.cpp
+++ lib/StaticAnalyzer/Checkers/ObjCContainersChecker.cpp
@@ -29,7 +29,8 @@
 
 namespace {
 class ObjCContainersChecker : public Checker< check::PreStmt<CallExpr>,
-                                             check::PostStmt<CallExpr> > {
+                                             check::PostStmt<CallExpr>,
+                                             check::PointerEscape> {
   mutable std::unique_ptr<BugType> BT;
   inline void initBugType() const {
     if (!BT)
@@ -52,6 +53,10 @@
 
   void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
   void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
+  ProgramStateRef checkPointerEscape(ProgramStateRef State,
+                                     const InvalidatedSymbols &Escaped,
+                                     const CallEvent *Call,
+                                     PointerEscapeKind Kind) const;
 };
 } // end anonymous namespace
 
@@ -145,6 +150,24 @@
   }
 }
 
+ProgramStateRef
+ObjCContainersChecker::checkPointerEscape(ProgramStateRef State,
+                                          const InvalidatedSymbols &Escaped,
+                                          const CallEvent *Call,
+                                          PointerEscapeKind Kind) const {
+  for (InvalidatedSymbols::const_iterator I = Escaped.begin(),
+                                          E = Escaped.end();
+                                          I != E; ++I) {
+    SymbolRef Sym = *I;
+    // When a symbol for a mutable array escapes, we can't reason precisely
+    // about its size any more -- so remove it from the map.
+    // Note that we aren't notified here when a CFMutableArrayRef escapes as a
+    // CFArrayRef. This is because CFArrayRef is typedef'd as a pointer to a
+    // const-qualified type.
+    State = State->remove<ArraySizeMap>(Sym);
+  }
+  return State;
+}
 /// Register checker.
 void ento::registerObjCContainersChecker(CheckerManager &mgr) {
   mgr.registerChecker<ObjCContainersChecker>();
Index: test/Analysis/CFContainers.mm
===================================================================
--- test/Analysis/CFContainers.mm
+++ test/Analysis/CFContainers.mm
@@ -19,6 +19,7 @@
 } CFArrayCallBacks;
 typedef const struct __CFArray * CFArrayRef;
 CFArrayRef CFArrayCreate(CFAllocatorRef allocator, const void **values, CFIndex numValues, const CFArrayCallBacks *callBacks);
+typedef struct __CFArray * CFMutableArrayRef;
 typedef const struct __CFString * CFStringRef;
 enum {
     kCFNumberSInt8Type = 1,
@@ -202,3 +203,24 @@
 void TestNullArray() {
   CFArrayGetValueAtIndex(0, 0);
 }
+
+void ArrayRefMutableEscape(CFMutableArrayRef a);
+void ArrayRefEscape(CFArrayRef a);
+
+void TestCFMutableArrayRefEscapeViaMutableArgument(CFMutableArrayRef a) {
+  CFIndex aLen = CFArrayGetCount(a);
+  ArrayRefMutableEscape(a);
+
+  // ArrayRefMutableEscape could mutate a to make it have
+  // at least aLen + 1 elements, so do not report an error here.
+  CFArrayGetValueAtIndex(a, aLen);
+}
+
+void TestCFMutableArrayRefEscapeViaImmutableArgument(CFMutableArrayRef a) {
+  CFIndex aLen = CFArrayGetCount(a);
+  ArrayRefEscape(a);
+
+  // ArrayRefEscape is declared to take a CFArrayRef (i.e, an immutable array)
+  // so we assume it does not change the length of a.
+  CFArrayGetValueAtIndex(a, aLen); // expected-warning {{Index is out of bounds}}
+}

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