Environment.cpp revision 651f13cea278ec967336033dd032faef0e9fc2ec 
1//== Environment.cpp - Map from Stmt* to Locations/Values -------*- 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 file defined the Environment and EnvironmentManager classes.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/AST/ExprCXX.h"
15#include "clang/AST/ExprObjC.h"
16#include "clang/Analysis/AnalysisContext.h"
17#include "clang/Analysis/CFG.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
19#include "llvm/Support/raw_ostream.h"
20
21using namespace clang;
22using namespace ento;
23
24static const Expr *ignoreTransparentExprs(const Expr *E) {
25  E = E->IgnoreParens();
26
27  switch (E->getStmtClass()) {
28  case Stmt::OpaqueValueExprClass:
29    E = cast<OpaqueValueExpr>(E)->getSourceExpr();
30    break;
31  case Stmt::ExprWithCleanupsClass:
32    E = cast<ExprWithCleanups>(E)->getSubExpr();
33    break;
34  case Stmt::CXXBindTemporaryExprClass:
35    E = cast<CXXBindTemporaryExpr>(E)->getSubExpr();
36    break;
37  case Stmt::SubstNonTypeTemplateParmExprClass:
38    E = cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement();
39    break;
40  default:
41    // This is the base case: we can't look through more than we already have.
42    return E;
43  }
44
45  return ignoreTransparentExprs(E);
46}
47
48static const Stmt *ignoreTransparentExprs(const Stmt *S) {
49  if (const Expr *E = dyn_cast<Expr>(S))
50    return ignoreTransparentExprs(E);
51  return S;
52}
53
54EnvironmentEntry::EnvironmentEntry(const Stmt *S, const LocationContext *L)
55  : std::pair<const Stmt *,
56              const StackFrameContext *>(ignoreTransparentExprs(S),
57                                         L ? L->getCurrentStackFrame() : 0) {}
58
59SVal Environment::lookupExpr(const EnvironmentEntry &E) const {
60  const SVal* X = ExprBindings.lookup(E);
61  if (X) {
62    SVal V = *X;
63    return V;
64  }
65  return UnknownVal();
66}
67
68SVal Environment::getSVal(const EnvironmentEntry &Entry,
69                          SValBuilder& svalBuilder) const {
70  const Stmt *S = Entry.getStmt();
71  const LocationContext *LCtx = Entry.getLocationContext();
72
73  switch (S->getStmtClass()) {
74  case Stmt::CXXBindTemporaryExprClass:
75  case Stmt::ExprWithCleanupsClass:
76  case Stmt::GenericSelectionExprClass:
77  case Stmt::OpaqueValueExprClass:
78  case Stmt::ParenExprClass:
79  case Stmt::SubstNonTypeTemplateParmExprClass:
80    llvm_unreachable("Should have been handled by ignoreTransparentExprs");
81
82  case Stmt::AddrLabelExprClass:
83  case Stmt::CharacterLiteralClass:
84  case Stmt::CXXBoolLiteralExprClass:
85  case Stmt::CXXScalarValueInitExprClass:
86  case Stmt::ImplicitValueInitExprClass:
87  case Stmt::IntegerLiteralClass:
88  case Stmt::ObjCBoolLiteralExprClass:
89  case Stmt::CXXNullPtrLiteralExprClass:
90  case Stmt::ObjCStringLiteralClass:
91  case Stmt::StringLiteralClass:
92    // Known constants; defer to SValBuilder.
93    return svalBuilder.getConstantVal(cast<Expr>(S)).getValue();
94
95  case Stmt::ReturnStmtClass: {
96    const ReturnStmt *RS = cast<ReturnStmt>(S);
97    if (const Expr *RE = RS->getRetValue())
98      return getSVal(EnvironmentEntry(RE, LCtx), svalBuilder);
99    return UndefinedVal();
100  }
101
102  // Handle all other Stmt* using a lookup.
103  default:
104    return lookupExpr(EnvironmentEntry(S, LCtx));
105  }
106}
107
108Environment EnvironmentManager::bindExpr(Environment Env,
109                                         const EnvironmentEntry &E,
110                                         SVal V,
111                                         bool Invalidate) {
112  if (V.isUnknown()) {
113    if (Invalidate)
114      return Environment(F.remove(Env.ExprBindings, E));
115    else
116      return Env;
117  }
118  return Environment(F.add(Env.ExprBindings, E, V));
119}
120
121namespace {
122class MarkLiveCallback : public SymbolVisitor {
123  SymbolReaper &SymReaper;
124public:
125  MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
126  bool VisitSymbol(SymbolRef sym) override {
127    SymReaper.markLive(sym);
128    return true;
129  }
130  bool VisitMemRegion(const MemRegion *R) override {
131    SymReaper.markLive(R);
132    return true;
133  }
134};
135} // end anonymous namespace
136
137// removeDeadBindings:
138//  - Remove subexpression bindings.
139//  - Remove dead block expression bindings.
140//  - Keep live block expression bindings:
141//   - Mark their reachable symbols live in SymbolReaper,
142//     see ScanReachableSymbols.
143//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
144Environment
145EnvironmentManager::removeDeadBindings(Environment Env,
146                                       SymbolReaper &SymReaper,
147                                       ProgramStateRef ST) {
148
149  // We construct a new Environment object entirely, as this is cheaper than
150  // individually removing all the subexpression bindings (which will greatly
151  // outnumber block-level expression bindings).
152  Environment NewEnv = getInitialEnvironment();
153
154  MarkLiveCallback CB(SymReaper);
155  ScanReachableSymbols RSScaner(ST, CB);
156
157  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
158    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
159             F.getTreeFactory());
160
161  // Iterate over the block-expr bindings.
162  for (Environment::iterator I = Env.begin(), E = Env.end();
163       I != E; ++I) {
164
165    const EnvironmentEntry &BlkExpr = I.getKey();
166    const SVal &X = I.getData();
167
168    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
169      // Copy the binding to the new map.
170      EBMapRef = EBMapRef.add(BlkExpr, X);
171
172      // If the block expr's value is a memory region, then mark that region.
173      if (Optional<loc::MemRegionVal> R = X.getAs<loc::MemRegionVal>())
174        SymReaper.markLive(R->getRegion());
175
176      // Mark all symbols in the block expr's value live.
177      RSScaner.scan(X);
178      continue;
179    } else {
180      SymExpr::symbol_iterator SI = X.symbol_begin(), SE = X.symbol_end();
181      for (; SI != SE; ++SI)
182        SymReaper.maybeDead(*SI);
183    }
184  }
185
186  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
187  return NewEnv;
188}
189
190void Environment::print(raw_ostream &Out, const char *NL,
191                        const char *Sep) const {
192  bool isFirst = true;
193
194  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
195    const EnvironmentEntry &En = I.getKey();
196
197    if (isFirst) {
198      Out << NL << NL
199          << "Expressions:"
200          << NL;
201      isFirst = false;
202    } else {
203      Out << NL;
204    }
205
206    const Stmt *S = En.getStmt();
207
208    Out << " (" << (const void*) En.getLocationContext() << ','
209      << (const void*) S << ") ";
210    LangOptions LO; // FIXME.
211    S->printPretty(Out, 0, PrintingPolicy(LO));
212    Out << " : " << I.getData();
213  }
214}
215