Add simpler checker to check if variables captured by a block are uninitialized.

llvm-svn: 96341

clang/include/clang/Checker/BugReporter/BugReporter.h

@@ -202,7 +202,7 @@ public:
   ~RangedBugReport();
 
   // FIXME: Move this out of line.
-  void addRange(SourceRange R) { 
+  void addRange(SourceRange R) {
     assert(R.isValid());
     Ranges.push_back(R);
   }
@@ -464,6 +464,10 @@ const Stmt *GetRetValExpr(const ExplodedNode *N);
 void registerTrackNullOrUndefValue(BugReporterContext& BRC, const void *stmt,
                                    const ExplodedNode* N);
 
+void registerFindLastStore(BugReporterContext& BRC, const void *memregion,
+                           const ExplodedNode *N);
+
+
 } // end namespace clang::bugreporter
 
 //===----------------------------------------------------------------------===//

clang/lib/Checker/BugReporterVisitors.cpp

@@ -323,7 +323,7 @@ void clang::bugreporter::registerTrackNullOrUndefValue(BugReporterContext& BRC,
 
       if (isa<loc::ConcreteInt>(V) || isa<nonloc::ConcreteInt>(V)
           || V.isUndef()) {
-        registerFindLastStore(BRC, R, V);
+        ::registerFindLastStore(BRC, R, V);
       }
     }
   }
@@ -347,3 +347,21 @@ void clang::bugreporter::registerTrackNullOrUndefValue(BugReporterContext& BRC,
     }
   }
 }
+
+void clang::bugreporter::registerFindLastStore(BugReporterContext& BRC,
+                                               const void *data,
+                                               const ExplodedNode* N) {
+
+  const MemRegion *R = static_cast<const MemRegion*>(data);
+
+  if (!R)
+    return;
+
+  const GRState *state = N->getState();
+  SVal V = state->getSVal(R);
+
+  if (V.isUnknown())
+    return;
+
+  BRC.addVisitor(new FindLastStoreBRVisitor(V, R));
+}

clang/lib/Checker/CMakeLists.txt

@@ -58,6 +58,7 @@ add_clang_library(clangChecker
   Store.cpp
   SymbolManager.cpp
   UndefBranchChecker.cpp
+  UndefCapturedBlockVarChecker.cpp
   UndefResultChecker.cpp
   UndefinedArraySubscriptChecker.cpp
   UndefinedAssignmentChecker.cpp

clang/lib/Checker/GRExprEngine.cpp

@@ -311,6 +311,7 @@ static void RegisterInternalChecks(GRExprEngine &Eng) {
   RegisterUndefinedArraySubscriptChecker(Eng);
   RegisterUndefinedAssignmentChecker(Eng);
   RegisterUndefBranchChecker(Eng);
+  RegisterUndefCapturedBlockVarChecker(Eng);
   RegisterUndefResultChecker(Eng);
 
   // This is not a checker yet.

clang/lib/Checker/GRExprEngineInternalChecks.h

@@ -36,8 +36,8 @@ void RegisterArrayBoundChecker(GRExprEngine &Eng);
 void RegisterUndefinedArraySubscriptChecker(GRExprEngine &Eng);
 void RegisterUndefinedAssignmentChecker(GRExprEngine &Eng);
 void RegisterUndefBranchChecker(GRExprEngine &Eng);
+void RegisterUndefCapturedBlockVarChecker(GRExprEngine &Eng);
 void RegisterUndefResultChecker(GRExprEngine &Eng);
-
 void RegisterNoReturnFunctionChecker(GRExprEngine &Eng);
 void RegisterBuiltinFunctionChecker(GRExprEngine &Eng);
 void RegisterOSAtomicChecker(GRExprEngine &Eng);

clang/lib/Checker/UndefCapturedBlockVarChecker.cpp

@@ -0,0 +1,101 @@
+// UndefCapturedBlockVarChecker.cpp - Uninitialized captured vars -*- C++ -*-=//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This checker detects blocks that capture uninitialized values.
+//
+//===----------------------------------------------------------------------===//
+
+#include "GRExprEngineInternalChecks.h"
+#include "clang/Checker/PathSensitive/CheckerVisitor.h"
+#include "clang/Checker/PathSensitive/GRExprEngine.h"
+#include "clang/Checker/BugReporter/BugReporter.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+
+namespace {
+class UndefCapturedBlockVarChecker
+  : public CheckerVisitor<UndefCapturedBlockVarChecker> {
+ BugType *BT;
+
+public:
+  UndefCapturedBlockVarChecker() : BT(0) {}
+  static void *getTag() { static int tag = 0; return &tag; }
+  void PostVisitBlockExpr(CheckerContext &C, const BlockExpr *BE);
+};
+} // end anonymous namespace
+
+void clang::RegisterUndefCapturedBlockVarChecker(GRExprEngine &Eng) {
+  Eng.registerCheck(new UndefCapturedBlockVarChecker());
+}
+
+static const BlockDeclRefExpr *FindBlockDeclRefExpr(const Stmt *S,
+                                                    const VarDecl *VD){
+  if (const BlockDeclRefExpr *BR = dyn_cast<BlockDeclRefExpr>(S))
+    if (BR->getDecl() == VD)
+      return BR;
+
+  for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
+       I!=E; ++I)
+    if (const Stmt *child = *I) {
+      const BlockDeclRefExpr *BR = FindBlockDeclRefExpr(child, VD);
+      if (BR)
+        return BR;
+    }
+
+  return NULL;
+}
+
+void
+UndefCapturedBlockVarChecker::PostVisitBlockExpr(CheckerContext &C,
+                                                 const BlockExpr *BE) {
+  if (!BE->hasBlockDeclRefExprs())
+    return;
+
+  const GRState *state = C.getState();
+  const BlockDataRegion *R =
+    cast<BlockDataRegion>(state->getSVal(BE).getAsRegion());
+
+  BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
+                                            E = R->referenced_vars_end();
+
+  for (; I != E; ++I) {
+    // This VarRegion is the region associated with the block; we need
+    // the one associated with the encompassing context.
+    const VarRegion *VR = *I;
+    const VarDecl *VD = VR->getDecl();
+
+    if (VD->getAttr<BlocksAttr>() || !VD->hasLocalStorage())
+      continue;
+
+    // Get the VarRegion associated with VD in the local stack frame.
+    const LocationContext *LC = C.getPredecessor()->getLocationContext();
+    VR = C.getValueManager().getRegionManager().getVarRegion(VD, LC);
+
+    if (state->getSVal(VR).isUndef())
+      if (ExplodedNode *N = C.GenerateSink()) {
+        if (!BT)
+          BT = new BuiltinBug("Captured block variable is uninitialized");
+
+        // Generate a bug report.
+        llvm::SmallString<128> buf;
+        llvm::raw_svector_ostream os(buf);
+
+        os << "Variable '" << VD->getName() << "' is captured by block with "
+              "a garbage value";
+
+        EnhancedBugReport *R = new EnhancedBugReport(*BT, os.str(), N);
+        if (const Expr *Ex = FindBlockDeclRefExpr(BE->getBody(), VD))
+          R->addRange(Ex->getSourceRange());
+        R->addVisitorCreator(bugreporter::registerFindLastStore, VR);
+        // need location of block
+        C.EmitReport(R);
+      }
+  }
+}

clang/test/Analysis/blocks.m

@@ -67,3 +67,19 @@ void test1(NSString *format, ...) {
 
   __builtin_va_end(args);
 }
+
+// test2 - Test that captured variables that are uninitialized are flagged
+// as such.
+void test2() {
+  static int y = 0;
+  int x;
+  ^{ y = x + 1; }();  // expected-warning{{Variable 'x' is captured by block with a garbage value}}
+}
+
+void test2_b() {
+  static int y = 0;
+  __block int x;
+  // This is also a bug, but should be found not by checking the value
+  // 'x' is bound at block creation.
+  ^{ y = x + 1; }(); // no-warning
+}