Environment.cpp revision 7affe151f5689b2d3547b8947c4099532c78a021 
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  case Stmt::CXXDefaultArgExprClass:
41    E = cast<CXXDefaultArgExpr>(E)->getExpr();
42    break;
43  default:
44    // This is the base case: we can't look through more than we already have.
45    return E;
46  }
47
48  return ignoreTransparentExprs(E);
49}
50
51static const Stmt *ignoreTransparentExprs(const Stmt *S) {
52  if (const Expr *E = dyn_cast<Expr>(S))
53    return ignoreTransparentExprs(E);
54  return S;
55}
56
57EnvironmentEntry::EnvironmentEntry(const Stmt *S, const LocationContext *L)
58  : std::pair<const Stmt *,
59              const StackFrameContext *>(ignoreTransparentExprs(S),
60                                         L ? L->getCurrentStackFrame() : 0) {}
61
62SVal Environment::lookupExpr(const EnvironmentEntry &E) const {
63  const SVal* X = ExprBindings.lookup(E);
64  if (X) {
65    SVal V = *X;
66    return V;
67  }
68  return UnknownVal();
69}
70
71SVal Environment::getSVal(const EnvironmentEntry &Entry,
72                          SValBuilder& svalBuilder) const {
73  const Stmt *S = Entry.getStmt();
74  const LocationContext *LCtx = Entry.getLocationContext();
75
76  switch (S->getStmtClass()) {
77  case Stmt::CXXBindTemporaryExprClass:
78  case Stmt::CXXDefaultArgExprClass:
79  case Stmt::ExprWithCleanupsClass:
80  case Stmt::GenericSelectionExprClass:
81  case Stmt::OpaqueValueExprClass:
82  case Stmt::ParenExprClass:
83  case Stmt::SubstNonTypeTemplateParmExprClass:
84    llvm_unreachable("Should have been handled by ignoreTransparentExprs");
85
86  case Stmt::AddrLabelExprClass:
87    return svalBuilder.makeLoc(cast<AddrLabelExpr>(S));
88
89  case Stmt::CharacterLiteralClass: {
90    const CharacterLiteral *C = cast<CharacterLiteral>(S);
91    return svalBuilder.makeIntVal(C->getValue(), C->getType());
92  }
93
94  case Stmt::CXXBoolLiteralExprClass:
95    return svalBuilder.makeBoolVal(cast<CXXBoolLiteralExpr>(S));
96
97  case Stmt::CXXScalarValueInitExprClass:
98  case Stmt::ImplicitValueInitExprClass: {
99    QualType Ty = cast<Expr>(S)->getType();
100    return svalBuilder.makeZeroVal(Ty);
101  }
102
103  case Stmt::IntegerLiteralClass:
104    return svalBuilder.makeIntVal(cast<IntegerLiteral>(S));
105
106  case Stmt::ObjCBoolLiteralExprClass:
107    return svalBuilder.makeBoolVal(cast<ObjCBoolLiteralExpr>(S));
108
109  // For special C0xx nullptr case, make a null pointer SVal.
110  case Stmt::CXXNullPtrLiteralExprClass:
111    return svalBuilder.makeNull();
112
113  case Stmt::ObjCStringLiteralClass: {
114    MemRegionManager &MRMgr = svalBuilder.getRegionManager();
115    const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(S);
116    return svalBuilder.makeLoc(MRMgr.getObjCStringRegion(SL));
117  }
118
119  case Stmt::StringLiteralClass: {
120    MemRegionManager &MRMgr = svalBuilder.getRegionManager();
121    const StringLiteral *SL = cast<StringLiteral>(S);
122    return svalBuilder.makeLoc(MRMgr.getStringRegion(SL));
123  }
124
125  case Stmt::ReturnStmtClass: {
126    const ReturnStmt *RS = cast<ReturnStmt>(S);
127    if (const Expr *RE = RS->getRetValue())
128      return getSVal(EnvironmentEntry(RE, LCtx), svalBuilder);
129    return UndefinedVal();
130  }
131
132  // Handle all other Stmt* using a lookup.
133  default:
134    break;
135  }
136
137  return lookupExpr(EnvironmentEntry(S, LCtx));
138}
139
140Environment EnvironmentManager::bindExpr(Environment Env,
141                                         const EnvironmentEntry &E,
142                                         SVal V,
143                                         bool Invalidate) {
144  if (V.isUnknown()) {
145    if (Invalidate)
146      return Environment(F.remove(Env.ExprBindings, E));
147    else
148      return Env;
149  }
150  return Environment(F.add(Env.ExprBindings, E, V));
151}
152
153namespace {
154class MarkLiveCallback : public SymbolVisitor {
155  SymbolReaper &SymReaper;
156public:
157  MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
158  bool VisitSymbol(SymbolRef sym) {
159    SymReaper.markLive(sym);
160    return true;
161  }
162  bool VisitMemRegion(const MemRegion *R) {
163    SymReaper.markLive(R);
164    return true;
165  }
166};
167} // end anonymous namespace
168
169// removeDeadBindings:
170//  - Remove subexpression bindings.
171//  - Remove dead block expression bindings.
172//  - Keep live block expression bindings:
173//   - Mark their reachable symbols live in SymbolReaper,
174//     see ScanReachableSymbols.
175//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
176Environment
177EnvironmentManager::removeDeadBindings(Environment Env,
178                                       SymbolReaper &SymReaper,
179                                       ProgramStateRef ST) {
180
181  // We construct a new Environment object entirely, as this is cheaper than
182  // individually removing all the subexpression bindings (which will greatly
183  // outnumber block-level expression bindings).
184  Environment NewEnv = getInitialEnvironment();
185
186  MarkLiveCallback CB(SymReaper);
187  ScanReachableSymbols RSScaner(ST, CB);
188
189  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
190    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
191             F.getTreeFactory());
192
193  // Iterate over the block-expr bindings.
194  for (Environment::iterator I = Env.begin(), E = Env.end();
195       I != E; ++I) {
196
197    const EnvironmentEntry &BlkExpr = I.getKey();
198    const SVal &X = I.getData();
199
200    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
201      // Copy the binding to the new map.
202      EBMapRef = EBMapRef.add(BlkExpr, X);
203
204      // If the block expr's value is a memory region, then mark that region.
205      if (isa<loc::MemRegionVal>(X)) {
206        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
207        SymReaper.markLive(R);
208      }
209
210      // Mark all symbols in the block expr's value live.
211      RSScaner.scan(X);
212      continue;
213    } else {
214      SymExpr::symbol_iterator SI = X.symbol_begin(), SE = X.symbol_end();
215      for (; SI != SE; ++SI)
216        SymReaper.maybeDead(*SI);
217    }
218  }
219
220  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
221  return NewEnv;
222}
223
224void Environment::print(raw_ostream &Out, const char *NL,
225                        const char *Sep) const {
226  bool isFirst = true;
227
228  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
229    const EnvironmentEntry &En = I.getKey();
230
231    if (isFirst) {
232      Out << NL << NL
233          << "Expressions:"
234          << NL;
235      isFirst = false;
236    } else {
237      Out << NL;
238    }
239
240    const Stmt *S = En.getStmt();
241
242    Out << " (" << (const void*) En.getLocationContext() << ','
243      << (const void*) S << ") ";
244    LangOptions LO; // FIXME.
245    S->printPretty(Out, 0, PrintingPolicy(LO));
246    Out << " : " << I.getData();
247  }
248}
249