Environment.cpp revision b66529d04727dc686b97ea3d937fc9785792f505 
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
20using namespace clang;
21using namespace ento;
22
23SVal Environment::lookupExpr(const EnvironmentEntry &E) const {
24  const SVal* X = ExprBindings.lookup(E);
25  if (X) {
26    SVal V = *X;
27    return V;
28  }
29  return UnknownVal();
30}
31
32SVal Environment::getSVal(const EnvironmentEntry &Entry,
33                          SValBuilder& svalBuilder,
34                          bool useOnlyDirectBindings) const {
35
36  if (useOnlyDirectBindings) {
37    // This branch is rarely taken, but can be exercised by
38    // checkers that explicitly bind values to arbitrary
39    // expressions.  It is crucial that we do not ignore any
40    // expression here, and do a direct lookup.
41    return lookupExpr(Entry);
42  }
43
44  const Stmt *E = Entry.getStmt();
45  const LocationContext *LCtx = Entry.getLocationContext();
46
47  for (;;) {
48    if (const Expr *Ex = dyn_cast<Expr>(E))
49      E = Ex->IgnoreParens();
50
51    switch (E->getStmtClass()) {
52      case Stmt::AddrLabelExprClass:
53        return svalBuilder.makeLoc(cast<AddrLabelExpr>(E));
54      case Stmt::OpaqueValueExprClass: {
55        const OpaqueValueExpr *ope = cast<OpaqueValueExpr>(E);
56        E = ope->getSourceExpr();
57        continue;
58      }
59      case Stmt::ParenExprClass:
60      case Stmt::GenericSelectionExprClass:
61        llvm_unreachable("ParenExprs and GenericSelectionExprs should "
62                         "have been handled by IgnoreParens()");
63      case Stmt::CharacterLiteralClass: {
64        const CharacterLiteral* C = cast<CharacterLiteral>(E);
65        return svalBuilder.makeIntVal(C->getValue(), C->getType());
66      }
67      case Stmt::CXXBoolLiteralExprClass: {
68        const SVal *X = ExprBindings.lookup(EnvironmentEntry(E, LCtx));
69        if (X)
70          return *X;
71        else
72          return svalBuilder.makeBoolVal(cast<CXXBoolLiteralExpr>(E));
73      }
74      case Stmt::CXXScalarValueInitExprClass:
75      case Stmt::ImplicitValueInitExprClass: {
76        QualType Ty = cast<Expr>(E)->getType();
77        return svalBuilder.makeZeroVal(Ty);
78      }
79      case Stmt::IntegerLiteralClass: {
80        // In C++, this expression may have been bound to a temporary object.
81        SVal const *X = ExprBindings.lookup(EnvironmentEntry(E, LCtx));
82        if (X)
83          return *X;
84        else
85          return svalBuilder.makeIntVal(cast<IntegerLiteral>(E));
86      }
87      case Stmt::ObjCBoolLiteralExprClass:
88        return svalBuilder.makeBoolVal(cast<ObjCBoolLiteralExpr>(E));
89
90      // For special C0xx nullptr case, make a null pointer SVal.
91      case Stmt::CXXNullPtrLiteralExprClass:
92        return svalBuilder.makeNull();
93      case Stmt::ExprWithCleanupsClass:
94        E = cast<ExprWithCleanups>(E)->getSubExpr();
95        continue;
96      case Stmt::CXXBindTemporaryExprClass:
97        E = cast<CXXBindTemporaryExpr>(E)->getSubExpr();
98        continue;
99      case Stmt::SubstNonTypeTemplateParmExprClass:
100        E = cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement();
101        continue;
102      case Stmt::CXXDefaultArgExprClass:
103        E = cast<CXXDefaultArgExpr>(E)->getExpr();
104        continue;
105      case Stmt::ObjCStringLiteralClass: {
106        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
107        const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
108        return svalBuilder.makeLoc(MRMgr.getObjCStringRegion(SL));
109      }
110      case Stmt::StringLiteralClass: {
111        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
112        const StringLiteral *SL = cast<StringLiteral>(E);
113        return svalBuilder.makeLoc(MRMgr.getStringRegion(SL));
114      }
115      case Stmt::ReturnStmtClass: {
116        const ReturnStmt *RS = cast<ReturnStmt>(E);
117        if (const Expr *RE = RS->getRetValue()) {
118          E = RE;
119          continue;
120        }
121        return UndefinedVal();
122      }
123
124      // Handle all other Stmt* using a lookup.
125      default:
126        break;
127    };
128    break;
129  }
130  return lookupExpr(EnvironmentEntry(E, LCtx));
131}
132
133Environment EnvironmentManager::bindExpr(Environment Env,
134                                         const EnvironmentEntry &E,
135                                         SVal V,
136                                         bool Invalidate) {
137  if (V.isUnknown()) {
138    if (Invalidate)
139      return Environment(F.remove(Env.ExprBindings, E));
140    else
141      return Env;
142  }
143  return Environment(F.add(Env.ExprBindings, E, V));
144}
145
146static inline EnvironmentEntry MakeLocation(const EnvironmentEntry &E) {
147  const Stmt *S = E.getStmt();
148  S = (const Stmt*) (((uintptr_t) S) | 0x1);
149  return EnvironmentEntry(S, E.getLocationContext());
150}
151
152Environment EnvironmentManager::bindExprAndLocation(Environment Env,
153                                                    const EnvironmentEntry &E,
154                                                    SVal location, SVal V) {
155  return Environment(F.add(F.add(Env.ExprBindings, MakeLocation(E), location),
156                           E, V));
157}
158
159namespace {
160class MarkLiveCallback : public SymbolVisitor {
161  SymbolReaper &SymReaper;
162public:
163  MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
164  bool VisitSymbol(SymbolRef sym) {
165    SymReaper.markLive(sym);
166    return true;
167  }
168  bool VisitMemRegion(const MemRegion *R) {
169    SymReaper.markLive(R);
170    return true;
171  }
172};
173} // end anonymous namespace
174
175// In addition to mapping from EnvironmentEntry - > SVals in the Environment,
176// we also maintain a mapping from EnvironmentEntry -> SVals (locations)
177// that were used during a load and store.
178static inline bool IsLocation(const EnvironmentEntry &E) {
179  const Stmt *S = E.getStmt();
180  return (bool) (((uintptr_t) S) & 0x1);
181}
182
183// removeDeadBindings:
184//  - Remove subexpression bindings.
185//  - Remove dead block expression bindings.
186//  - Keep live block expression bindings:
187//   - Mark their reachable symbols live in SymbolReaper,
188//     see ScanReachableSymbols.
189//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
190Environment
191EnvironmentManager::removeDeadBindings(Environment Env,
192                                       SymbolReaper &SymReaper,
193                                       ProgramStateRef ST) {
194
195  // We construct a new Environment object entirely, as this is cheaper than
196  // individually removing all the subexpression bindings (which will greatly
197  // outnumber block-level expression bindings).
198  Environment NewEnv = getInitialEnvironment();
199
200  SmallVector<std::pair<EnvironmentEntry, SVal>, 10> deferredLocations;
201
202  MarkLiveCallback CB(SymReaper);
203  ScanReachableSymbols RSScaner(ST, CB);
204
205  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
206    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
207             F.getTreeFactory());
208
209  // Iterate over the block-expr bindings.
210  for (Environment::iterator I = Env.begin(), E = Env.end();
211       I != E; ++I) {
212
213    const EnvironmentEntry &BlkExpr = I.getKey();
214    // For recorded locations (used when evaluating loads and stores), we
215    // consider them live only when their associated normal expression is
216    // also live.
217    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
218    // still have an entry in the map.
219    if (IsLocation(BlkExpr)) {
220      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
221      continue;
222    }
223    const SVal &X = I.getData();
224
225    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
226      // Copy the binding to the new map.
227      EBMapRef = EBMapRef.add(BlkExpr, X);
228
229      // If the block expr's value is a memory region, then mark that region.
230      if (isa<loc::MemRegionVal>(X)) {
231        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
232        SymReaper.markLive(R);
233      }
234
235      // Mark all symbols in the block expr's value live.
236      RSScaner.scan(X);
237      continue;
238    }
239  }
240
241  // Go through he deferred locations and add them to the new environment if
242  // the correspond Stmt* is in the map as well.
243  for (SmallVectorImpl<std::pair<EnvironmentEntry, SVal> >::iterator
244      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
245    const EnvironmentEntry &En = I->first;
246    const Stmt *S = (Stmt*) (((uintptr_t) En.getStmt()) & (uintptr_t) ~0x1);
247    if (EBMapRef.lookup(EnvironmentEntry(S, En.getLocationContext())))
248      EBMapRef = EBMapRef.add(En, I->second);
249  }
250
251  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
252  return NewEnv;
253}
254
255void Environment::print(raw_ostream &Out, const char *NL,
256                        const char *Sep) const {
257  printAux(Out, false, NL, Sep);
258  printAux(Out, true, NL, Sep);
259}
260
261void Environment::printAux(raw_ostream &Out, bool printLocations,
262                           const char *NL,
263                           const char *Sep) const{
264
265  bool isFirst = true;
266
267  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
268    const EnvironmentEntry &En = I.getKey();
269    if (IsLocation(En)) {
270      if (!printLocations)
271        continue;
272    }
273    else {
274      if (printLocations)
275        continue;
276    }
277
278    if (isFirst) {
279      Out << NL << NL
280          << (printLocations ? "Load/Store locations:" : "Expressions:")
281          << NL;
282      isFirst = false;
283    } else {
284      Out << NL;
285    }
286
287    const Stmt *S = En.getStmt();
288    if (printLocations) {
289      S = (Stmt*) (((uintptr_t) S) & ((uintptr_t) ~0x1));
290    }
291
292    Out << " (" << (void*) En.getLocationContext() << ',' << (void*) S << ") ";
293    LangOptions LO; // FIXME.
294    S->printPretty(Out, 0, PrintingPolicy(LO));
295    Out << " : " << I.getData();
296  }
297}
298