Environment.cpp revision 234353 
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::IntegerLiteralClass: {
75        // In C++, this expression may have been bound to a temporary object.
76        SVal const *X = ExprBindings.lookup(EnvironmentEntry(E, LCtx));
77        if (X)
78          return *X;
79        else
80          return svalBuilder.makeIntVal(cast<IntegerLiteral>(E));
81      }
82      case Stmt::ObjCBoolLiteralExprClass:
83        return svalBuilder.makeBoolVal(cast<ObjCBoolLiteralExpr>(E));
84
85      // For special C0xx nullptr case, make a null pointer SVal.
86      case Stmt::CXXNullPtrLiteralExprClass:
87        return svalBuilder.makeNull();
88      case Stmt::ExprWithCleanupsClass:
89        E = cast<ExprWithCleanups>(E)->getSubExpr();
90        continue;
91      case Stmt::CXXBindTemporaryExprClass:
92        E = cast<CXXBindTemporaryExpr>(E)->getSubExpr();
93        continue;
94      case Stmt::ObjCPropertyRefExprClass:
95        return loc::ObjCPropRef(cast<ObjCPropertyRefExpr>(E));
96      case Stmt::ObjCStringLiteralClass: {
97        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
98        const ObjCStringLiteral *SL = cast<ObjCStringLiteral>(E);
99        return svalBuilder.makeLoc(MRMgr.getObjCStringRegion(SL));
100      }
101      case Stmt::StringLiteralClass: {
102        MemRegionManager &MRMgr = svalBuilder.getRegionManager();
103        const StringLiteral *SL = cast<StringLiteral>(E);
104        return svalBuilder.makeLoc(MRMgr.getStringRegion(SL));
105      }
106      case Stmt::ReturnStmtClass: {
107        const ReturnStmt *RS = cast<ReturnStmt>(E);
108        if (const Expr *RE = RS->getRetValue()) {
109          E = RE;
110          continue;
111        }
112        return UndefinedVal();
113      }
114
115      // Handle all other Stmt* using a lookup.
116      default:
117        break;
118    };
119    break;
120  }
121  return lookupExpr(EnvironmentEntry(E, LCtx));
122}
123
124Environment EnvironmentManager::bindExpr(Environment Env,
125                                         const EnvironmentEntry &E,
126                                         SVal V,
127                                         bool Invalidate) {
128  if (V.isUnknown()) {
129    if (Invalidate)
130      return Environment(F.remove(Env.ExprBindings, E));
131    else
132      return Env;
133  }
134  return Environment(F.add(Env.ExprBindings, E, V));
135}
136
137static inline EnvironmentEntry MakeLocation(const EnvironmentEntry &E) {
138  const Stmt *S = E.getStmt();
139  S = (const Stmt*) (((uintptr_t) S) | 0x1);
140  return EnvironmentEntry(S, E.getLocationContext());
141}
142
143Environment EnvironmentManager::bindExprAndLocation(Environment Env,
144                                                    const EnvironmentEntry &E,
145                                                    SVal location, SVal V) {
146  return Environment(F.add(F.add(Env.ExprBindings, MakeLocation(E), location),
147                           E, V));
148}
149
150namespace {
151class MarkLiveCallback : public SymbolVisitor {
152  SymbolReaper &SymReaper;
153public:
154  MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
155  bool VisitSymbol(SymbolRef sym) {
156    SymReaper.markLive(sym);
157    return true;
158  }
159  bool VisitMemRegion(const MemRegion *R) {
160    SymReaper.markLive(R);
161    return true;
162  }
163};
164} // end anonymous namespace
165
166// In addition to mapping from EnvironmentEntry - > SVals in the Environment,
167// we also maintain a mapping from EnvironmentEntry -> SVals (locations)
168// that were used during a load and store.
169static inline bool IsLocation(const EnvironmentEntry &E) {
170  const Stmt *S = E.getStmt();
171  return (bool) (((uintptr_t) S) & 0x1);
172}
173
174// removeDeadBindings:
175//  - Remove subexpression bindings.
176//  - Remove dead block expression bindings.
177//  - Keep live block expression bindings:
178//   - Mark their reachable symbols live in SymbolReaper,
179//     see ScanReachableSymbols.
180//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
181Environment
182EnvironmentManager::removeDeadBindings(Environment Env,
183                                       SymbolReaper &SymReaper,
184                                       ProgramStateRef ST) {
185
186  // We construct a new Environment object entirely, as this is cheaper than
187  // individually removing all the subexpression bindings (which will greatly
188  // outnumber block-level expression bindings).
189  Environment NewEnv = getInitialEnvironment();
190
191  SmallVector<std::pair<EnvironmentEntry, SVal>, 10> deferredLocations;
192
193  MarkLiveCallback CB(SymReaper);
194  ScanReachableSymbols RSScaner(ST, CB);
195
196  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
197    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
198             F.getTreeFactory());
199
200  // Iterate over the block-expr bindings.
201  for (Environment::iterator I = Env.begin(), E = Env.end();
202       I != E; ++I) {
203
204    const EnvironmentEntry &BlkExpr = I.getKey();
205    // For recorded locations (used when evaluating loads and stores), we
206    // consider them live only when their associated normal expression is
207    // also live.
208    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
209    // still have an entry in the map.
210    if (IsLocation(BlkExpr)) {
211      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
212      continue;
213    }
214    const SVal &X = I.getData();
215
216    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
217      // Copy the binding to the new map.
218      EBMapRef = EBMapRef.add(BlkExpr, X);
219
220      // If the block expr's value is a memory region, then mark that region.
221      if (isa<loc::MemRegionVal>(X)) {
222        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
223        SymReaper.markLive(R);
224      }
225
226      // Mark all symbols in the block expr's value live.
227      RSScaner.scan(X);
228      continue;
229    }
230
231    // Otherwise the expression is dead with a couple exceptions.
232    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
233    // beginning of itself, but we need its UndefinedVal to determine its
234    // SVal.
235    if (X.isUndef() && cast<UndefinedVal>(X).getData())
236      EBMapRef = EBMapRef.add(BlkExpr, X);
237  }
238
239  // Go through he deferred locations and add them to the new environment if
240  // the correspond Stmt* is in the map as well.
241  for (SmallVectorImpl<std::pair<EnvironmentEntry, SVal> >::iterator
242      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
243    const EnvironmentEntry &En = I->first;
244    const Stmt *S = (Stmt*) (((uintptr_t) En.getStmt()) & (uintptr_t) ~0x1);
245    if (EBMapRef.lookup(EnvironmentEntry(S, En.getLocationContext())))
246      EBMapRef = EBMapRef.add(En, I->second);
247  }
248
249  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
250  return NewEnv;
251}
252
253void Environment::print(raw_ostream &Out, const char *NL,
254                        const char *Sep) const {
255  printAux(Out, false, NL, Sep);
256  printAux(Out, true, NL, Sep);
257}
258
259void Environment::printAux(raw_ostream &Out, bool printLocations,
260                           const char *NL,
261                           const char *Sep) const{
262
263  bool isFirst = true;
264
265  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
266    const EnvironmentEntry &En = I.getKey();
267    if (IsLocation(En)) {
268      if (!printLocations)
269        continue;
270    }
271    else {
272      if (printLocations)
273        continue;
274    }
275
276    if (isFirst) {
277      Out << NL << NL
278          << (printLocations ? "Load/Store locations:" : "Expressions:")
279          << NL;
280      isFirst = false;
281    } else {
282      Out << NL;
283    }
284
285    const Stmt *S = En.getStmt();
286    if (printLocations) {
287      S = (Stmt*) (((uintptr_t) S) & ((uintptr_t) ~0x1));
288    }
289
290    Out << " (" << (void*) En.getLocationContext() << ',' << (void*) S << ") ";
291    LangOptions LO; // FIXME.
292    S->printPretty(Out, 0, PrintingPolicy(LO));
293    Out << " : " << I.getData();
294  }
295}
296