Environment.cpp revision 4ccc4cc5d4e7c5c436d5f45065d3639cfc7c6e48 
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::ObjCStringLiteralClass: {
100        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
101        const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
102        return svalBuilder.makeLoc(MRMgr.getObjCStringRegion(SL));
103      }
104      case Stmt::StringLiteralClass: {
105        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
106        const StringLiteral *SL = cast<StringLiteral>(E);
107        return svalBuilder.makeLoc(MRMgr.getStringRegion(SL));
108      }
109      case Stmt::ReturnStmtClass: {
110        const ReturnStmt *RS = cast<ReturnStmt>(E);
111        if (const Expr *RE = RS->getRetValue()) {
112          E = RE;
113          continue;
114        }
115        return UndefinedVal();
116      }
117
118      // Handle all other Stmt* using a lookup.
119      default:
120        break;
121    };
122    break;
123  }
124  return lookupExpr(EnvironmentEntry(E, LCtx));
125}
126
127Environment EnvironmentManager::bindExpr(Environment Env,
128                                         const EnvironmentEntry &E,
129                                         SVal V,
130                                         bool Invalidate) {
131  if (V.isUnknown()) {
132    if (Invalidate)
133      return Environment(F.remove(Env.ExprBindings, E));
134    else
135      return Env;
136  }
137  return Environment(F.add(Env.ExprBindings, E, V));
138}
139
140static inline EnvironmentEntry MakeLocation(const EnvironmentEntry &E) {
141  const Stmt *S = E.getStmt();
142  S = (const Stmt*) (((uintptr_t) S) | 0x1);
143  return EnvironmentEntry(S, E.getLocationContext());
144}
145
146Environment EnvironmentManager::bindExprAndLocation(Environment Env,
147                                                    const EnvironmentEntry &E,
148                                                    SVal location, SVal V) {
149  return Environment(F.add(F.add(Env.ExprBindings, MakeLocation(E), location),
150                           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// In addition to mapping from EnvironmentEntry - > SVals in the Environment,
170// we also maintain a mapping from EnvironmentEntry -> SVals (locations)
171// that were used during a load and store.
172static inline bool IsLocation(const EnvironmentEntry &E) {
173  const Stmt *S = E.getStmt();
174  return (bool) (((uintptr_t) S) & 0x1);
175}
176
177// removeDeadBindings:
178//  - Remove subexpression bindings.
179//  - Remove dead block expression bindings.
180//  - Keep live block expression bindings:
181//   - Mark their reachable symbols live in SymbolReaper,
182//     see ScanReachableSymbols.
183//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
184Environment
185EnvironmentManager::removeDeadBindings(Environment Env,
186                                       SymbolReaper &SymReaper,
187                                       ProgramStateRef ST) {
188
189  // We construct a new Environment object entirely, as this is cheaper than
190  // individually removing all the subexpression bindings (which will greatly
191  // outnumber block-level expression bindings).
192  Environment NewEnv = getInitialEnvironment();
193
194  SmallVector<std::pair<EnvironmentEntry, SVal>, 10> deferredLocations;
195
196  MarkLiveCallback CB(SymReaper);
197  ScanReachableSymbols RSScaner(ST, CB);
198
199  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
200    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
201             F.getTreeFactory());
202
203  // Iterate over the block-expr bindings.
204  for (Environment::iterator I = Env.begin(), E = Env.end();
205       I != E; ++I) {
206
207    const EnvironmentEntry &BlkExpr = I.getKey();
208    // For recorded locations (used when evaluating loads and stores), we
209    // consider them live only when their associated normal expression is
210    // also live.
211    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
212    // still have an entry in the map.
213    if (IsLocation(BlkExpr)) {
214      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
215      continue;
216    }
217    const SVal &X = I.getData();
218
219    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
220      // Copy the binding to the new map.
221      EBMapRef = EBMapRef.add(BlkExpr, X);
222
223      // If the block expr's value is a memory region, then mark that region.
224      if (isa<loc::MemRegionVal>(X)) {
225        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
226        SymReaper.markLive(R);
227      }
228
229      // Mark all symbols in the block expr's value live.
230      RSScaner.scan(X);
231      continue;
232    }
233
234    // Otherwise the expression is dead with a couple exceptions.
235    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
236    // beginning of itself, but we need its UndefinedVal to determine its
237    // SVal.
238    if (X.isUndef() && cast<UndefinedVal>(X).getData())
239      EBMapRef = EBMapRef.add(BlkExpr, X);
240  }
241
242  // Go through he deferred locations and add them to the new environment if
243  // the correspond Stmt* is in the map as well.
244  for (SmallVectorImpl<std::pair<EnvironmentEntry, SVal> >::iterator
245      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
246    const EnvironmentEntry &En = I->first;
247    const Stmt *S = (Stmt*) (((uintptr_t) En.getStmt()) & (uintptr_t) ~0x1);
248    if (EBMapRef.lookup(EnvironmentEntry(S, En.getLocationContext())))
249      EBMapRef = EBMapRef.add(En, I->second);
250  }
251
252  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
253  return NewEnv;
254}
255
256void Environment::print(raw_ostream &Out, const char *NL,
257                        const char *Sep) const {
258  printAux(Out, false, NL, Sep);
259  printAux(Out, true, NL, Sep);
260}
261
262void Environment::printAux(raw_ostream &Out, bool printLocations,
263                           const char *NL,
264                           const char *Sep) const{
265
266  bool isFirst = true;
267
268  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
269    const EnvironmentEntry &En = I.getKey();
270    if (IsLocation(En)) {
271      if (!printLocations)
272        continue;
273    }
274    else {
275      if (printLocations)
276        continue;
277    }
278
279    if (isFirst) {
280      Out << NL << NL
281          << (printLocations ? "Load/Store locations:" : "Expressions:")
282          << NL;
283      isFirst = false;
284    } else {
285      Out << NL;
286    }
287
288    const Stmt *S = En.getStmt();
289    if (printLocations) {
290      S = (Stmt*) (((uintptr_t) S) & ((uintptr_t) ~0x1));
291    }
292
293    Out << " (" << (void*) En.getLocationContext() << ',' << (void*) S << ") ";
294    LangOptions LO; // FIXME.
295    S->printPretty(Out, 0, PrintingPolicy(LO));
296    Out << " : " << I.getData();
297  }
298}
299