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 (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
44 I!=E; ++I)
45 if (const Stmt *child = *I) {
46 const DeclRefExpr *BR = FindBlockDeclRefExpr(child, VD);
47 if (BR)
48 return BR;
49 }
50
51 return nullptr;
52 }
53
54 void
checkPostStmt(const BlockExpr * BE,CheckerContext & C) const55 UndefCapturedBlockVarChecker::checkPostStmt(const BlockExpr *BE,
56 CheckerContext &C) const {
57 if (!BE->getBlockDecl()->hasCaptures())
58 return;
59
60 ProgramStateRef state = C.getState();
61 const BlockDataRegion *R =
62 cast<BlockDataRegion>(state->getSVal(BE,
63 C.getLocationContext()).getAsRegion());
64
65 BlockDataRegion::referenced_vars_iterator I = R->referenced_vars_begin(),
66 E = R->referenced_vars_end();
67
68 for (; I != E; ++I) {
69 // This VarRegion is the region associated with the block; we need
70 // the one associated with the encompassing context.
71 const VarRegion *VR = I.getCapturedRegion();
72 const VarDecl *VD = VR->getDecl();
73
74 if (VD->hasAttr<BlocksAttr>() || !VD->hasLocalStorage())
75 continue;
76
77 // Get the VarRegion associated with VD in the local stack frame.
78 if (Optional<UndefinedVal> V =
79 state->getSVal(I.getOriginalRegion()).getAs<UndefinedVal>()) {
80 if (ExplodedNode *N = C.generateSink()) {
81 if (!BT)
82 BT.reset(
83 new BuiltinBug(this, "uninitialized variable captured by block"));
84
85 // Generate a bug report.
86 SmallString<128> buf;
87 llvm::raw_svector_ostream os(buf);
88
89 os << "Variable '" << VD->getName()
90 << "' is uninitialized when captured by block";
91
92 BugReport *R = new BugReport(*BT, os.str(), N);
93 if (const Expr *Ex = FindBlockDeclRefExpr(BE->getBody(), VD))
94 R->addRange(Ex->getSourceRange());
95 R->addVisitor(new FindLastStoreBRVisitor(*V, VR,
96 /*EnableNullFPSuppression*/false));
97 R->disablePathPruning();
98 // need location of block
99 C.emitReport(R);
100 }
101 }
102 }
103 }
104
registerUndefCapturedBlockVarChecker(CheckerManager & mgr)105 void ento::registerUndefCapturedBlockVarChecker(CheckerManager &mgr) {
106 mgr.registerChecker<UndefCapturedBlockVarChecker>();
107 }
108