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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/AST/Attr.h"
16 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
17 #include "clang/StaticAnalyzer/Core/Checker.h"
18 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
20 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
21 #include "llvm/ADT/SmallString.h"
22 #include "llvm/Support/raw_ostream.h"
23 
24 using namespace clang;
25 using namespace ento;
26 
27 namespace {
28 class UndefCapturedBlockVarChecker
29   : public Checker< check::PostStmt<BlockExpr> > {
30   mutable std::unique_ptr<BugType> BT;
31 
32 public:
33   void checkPostStmt(const BlockExpr *BE, CheckerContext &C) const;
34 };
35 } // end anonymous namespace
36 
FindBlockDeclRefExpr(const Stmt * S,const VarDecl * VD)37 static const DeclRefExpr *FindBlockDeclRefExpr(const Stmt *S,
38                                                const VarDecl *VD) {
39   if (const DeclRefExpr *BR = dyn_cast<DeclRefExpr>(S))
40     if (BR->getDecl() == VD)
41       return BR;
42 
43   for (const Stmt *Child : S->children())
44     if (Child)
45       if (const DeclRefExpr *BR = FindBlockDeclRefExpr(Child, VD))
46         return BR;
47 
48   return nullptr;
49 }
50 
51 void
checkPostStmt(const BlockExpr * BE,CheckerContext & C) const52 UndefCapturedBlockVarChecker::checkPostStmt(const BlockExpr *BE,
53                                             CheckerContext &C) const {
54   if (!BE->getBlockDecl()->hasCaptures())
55     return;
56 
57   ProgramStateRef state = C.getState();
58   const BlockDataRegion *R =
59     cast<BlockDataRegion>(state->getSVal(BE,
60                                          C.getLocationContext()).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.getCapturedRegion();
69     const VarDecl *VD = VR->getDecl();
70 
71     if (VD->hasAttr<BlocksAttr>() || !VD->hasLocalStorage())
72       continue;
73 
74     // Get the VarRegion associated with VD in the local stack frame.
75     if (Optional<UndefinedVal> V =
76           state->getSVal(I.getOriginalRegion()).getAs<UndefinedVal>()) {
77       if (ExplodedNode *N = C.generateErrorNode()) {
78         if (!BT)
79           BT.reset(
80               new BuiltinBug(this, "uninitialized variable captured by block"));
81 
82         // Generate a bug report.
83         SmallString<128> buf;
84         llvm::raw_svector_ostream os(buf);
85 
86         os << "Variable '" << VD->getName()
87            << "' is uninitialized when captured by block";
88 
89         auto R = llvm::make_unique<BugReport>(*BT, os.str(), N);
90         if (const Expr *Ex = FindBlockDeclRefExpr(BE->getBody(), VD))
91           R->addRange(Ex->getSourceRange());
92         R->addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
93             *V, VR, /*EnableNullFPSuppression*/ false));
94         R->disablePathPruning();
95         // need location of block
96         C.emitReport(std::move(R));
97       }
98     }
99   }
100 }
101 
registerUndefCapturedBlockVarChecker(CheckerManager & mgr)102 void ento::registerUndefCapturedBlockVarChecker(CheckerManager &mgr) {
103   mgr.registerChecker<UndefCapturedBlockVarChecker>();
104 }
105