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1 // UndefCapturedBlockVarChecker.cpp - Uninitialized captured vars -*- C++ -*-=//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This checker detects blocks that capture uninitialized values.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "ClangSACheckers.h"
15 #include "clang/StaticAnalyzer/Core/Checker.h"
16 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
20 #include "llvm/Support/raw_ostream.h"
21 
22 using namespace clang;
23 using namespace ento;
24 
25 namespace {
26 class UndefCapturedBlockVarChecker
27   : public Checker< check::PostStmt<BlockExpr> > {
28  mutable llvm::OwningPtr<BugType> BT;
29 
30 public:
31   void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
32 };
33 } // end anonymous namespace
34 
FindBlockDeclRefExpr(const Stmt * S,const VarDecl * VD)35 static const BlockDeclRefExpr *FindBlockDeclRefExpr(const Stmt *S,
36                                                     const VarDecl *VD){
37   if (const BlockDeclRefExpr *BR = dyn_cast<BlockDeclRefExpr>(S))
38     if (BR->getDecl() == VD)
39       return BR;
40 
41   for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
42        I!=E; ++I)
43     if (const Stmt *child = *I) {
44       const BlockDeclRefExpr *BR = FindBlockDeclRefExpr(child, VD);
45       if (BR)
46         return BR;
47     }
48 
49   return NULL;
50 }
51 
52 void
checkPostStmt(const BlockExpr * BE,CheckerContext & C) const53 UndefCapturedBlockVarChecker::checkPostStmt(const BlockExpr *BE,
54                                             CheckerContext &C) const {
55   if (!BE->getBlockDecl()->hasCaptures())
56     return;
57 
58   const GRState *state = C.getState();
59   const BlockDataRegion *R =
60     cast<BlockDataRegion>(state->getSVal(BE).getAsRegion());
61 
62   BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
63                                             E = R->referenced_vars_end();
64 
65   for (; I != E; ++I) {
66     // This VarRegion is the region associated with the block; we need
67     // the one associated with the encompassing context.
68     const VarRegion *VR = *I;
69     const VarDecl *VD = VR->getDecl();
70 
71     if (VD->getAttr<BlocksAttr>() || !VD->hasLocalStorage())
72       continue;
73 
74     // Get the VarRegion associated with VD in the local stack frame.
75     const LocationContext *LC = C.getPredecessor()->getLocationContext();
76     VR = C.getSValBuilder().getRegionManager().getVarRegion(VD, LC);
77 
78     if (state->getSVal(VR).isUndef())
79       if (ExplodedNode *N = C.generateSink()) {
80         if (!BT)
81           BT.reset(new BuiltinBug("uninitialized variable captured by block"));
82 
83         // Generate a bug report.
84         llvm::SmallString<128> buf;
85         llvm::raw_svector_ostream os(buf);
86 
87         os << "Variable '" << VD->getName()
88            << "' is uninitialized when captured by block";
89 
90         EnhancedBugReport *R = new EnhancedBugReport(*BT, os.str(), N);
91         if (const Expr *Ex = FindBlockDeclRefExpr(BE->getBody(), VD))
92           R->addRange(Ex->getSourceRange());
93         R->addVisitorCreator(bugreporter::registerFindLastStore, VR);
94         // need location of block
95         C.EmitReport(R);
96       }
97   }
98 }
99 
registerUndefCapturedBlockVarChecker(CheckerManager & mgr)100 void ento::registerUndefCapturedBlockVarChecker(CheckerManager &mgr) {
101   mgr.registerChecker<UndefCapturedBlockVarChecker>();
102 }
103