Environment.cpp revision 7f9b1d963d4b7e2faff7305733e3453130b402fe 
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      // For special C0xx nullptr case, make a null pointer SVal.
83      case Stmt::CXXNullPtrLiteralExprClass:
84        return svalBuilder.makeNull();
85      case Stmt::ExprWithCleanupsClass:
86        E = cast<ExprWithCleanups>(E)->getSubExpr();
87        continue;
88      case Stmt::CXXBindTemporaryExprClass:
89        E = cast<CXXBindTemporaryExpr>(E)->getSubExpr();
90        continue;
91      case Stmt::ObjCPropertyRefExprClass:
92        return loc::ObjCPropRef(cast<ObjCPropertyRefExpr>(E));
93      case Stmt::ReturnStmtClass: {
94        const ReturnStmt *RS = cast<ReturnStmt>(E);
95        if (const Expr *RE = RS->getRetValue()) {
96          E = RE;
97          continue;
98        }
99        return UndefinedVal();
100      }
101
102      // Handle all other Stmt* using a lookup.
103      default:
104        break;
105    };
106    break;
107  }
108  return lookupExpr(EnvironmentEntry(E, LCtx));
109}
110
111Environment EnvironmentManager::bindExpr(Environment Env,
112                                         const EnvironmentEntry &E,
113                                         SVal V,
114                                         bool Invalidate) {
115  if (V.isUnknown()) {
116    if (Invalidate)
117      return Environment(F.remove(Env.ExprBindings, E));
118    else
119      return Env;
120  }
121  return Environment(F.add(Env.ExprBindings, E, V));
122}
123
124static inline EnvironmentEntry MakeLocation(const EnvironmentEntry &E) {
125  const Stmt *S = E.getStmt();
126  S = (const Stmt*) (((uintptr_t) S) | 0x1);
127  return EnvironmentEntry(S, E.getLocationContext());
128}
129
130Environment EnvironmentManager::bindExprAndLocation(Environment Env,
131                                                    const EnvironmentEntry &E,
132                                                    SVal location, SVal V) {
133  return Environment(F.add(F.add(Env.ExprBindings, MakeLocation(E), location),
134                           E, V));
135}
136
137namespace {
138class MarkLiveCallback : public SymbolVisitor {
139  SymbolReaper &SymReaper;
140public:
141  MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
142  bool VisitSymbol(SymbolRef sym) {
143    SymReaper.markLive(sym);
144    return true;
145  }
146  bool VisitMemRegion(const MemRegion *R) {
147    SymReaper.markLive(R);
148    return true;
149  }
150};
151} // end anonymous namespace
152
153// In addition to mapping from EnvironmentEntry - > SVals in the Environment,
154// we also maintain a mapping from EnvironmentEntry -> SVals (locations)
155// that were used during a load and store.
156static inline bool IsLocation(const EnvironmentEntry &E) {
157  const Stmt *S = E.getStmt();
158  return (bool) (((uintptr_t) S) & 0x1);
159}
160
161// removeDeadBindings:
162//  - Remove subexpression bindings.
163//  - Remove dead block expression bindings.
164//  - Keep live block expression bindings:
165//   - Mark their reachable symbols live in SymbolReaper,
166//     see ScanReachableSymbols.
167//   - Mark the region in DRoots if the binding is a loc::MemRegionVal.
168Environment
169EnvironmentManager::removeDeadBindings(Environment Env,
170                                       SymbolReaper &SymReaper,
171                                       ProgramStateRef ST) {
172
173  // We construct a new Environment object entirely, as this is cheaper than
174  // individually removing all the subexpression bindings (which will greatly
175  // outnumber block-level expression bindings).
176  Environment NewEnv = getInitialEnvironment();
177
178  SmallVector<std::pair<EnvironmentEntry, SVal>, 10> deferredLocations;
179
180  MarkLiveCallback CB(SymReaper);
181  ScanReachableSymbols RSScaner(ST, CB);
182
183  llvm::ImmutableMapRef<EnvironmentEntry,SVal>
184    EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
185             F.getTreeFactory());
186
187  // Iterate over the block-expr bindings.
188  for (Environment::iterator I = Env.begin(), E = Env.end();
189       I != E; ++I) {
190
191    const EnvironmentEntry &BlkExpr = I.getKey();
192    // For recorded locations (used when evaluating loads and stores), we
193    // consider them live only when their associated normal expression is
194    // also live.
195    // NOTE: This assumes that loads/stores that evaluated to UnknownVal
196    // still have an entry in the map.
197    if (IsLocation(BlkExpr)) {
198      deferredLocations.push_back(std::make_pair(BlkExpr, I.getData()));
199      continue;
200    }
201    const SVal &X = I.getData();
202
203    if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
204      // Copy the binding to the new map.
205      EBMapRef = EBMapRef.add(BlkExpr, X);
206
207      // If the block expr's value is a memory region, then mark that region.
208      if (isa<loc::MemRegionVal>(X)) {
209        const MemRegion *R = cast<loc::MemRegionVal>(X).getRegion();
210        SymReaper.markLive(R);
211      }
212
213      // Mark all symbols in the block expr's value live.
214      RSScaner.scan(X);
215      continue;
216    }
217
218    // Otherwise the expression is dead with a couple exceptions.
219    // Do not misclean LogicalExpr or ConditionalOperator.  It is dead at the
220    // beginning of itself, but we need its UndefinedVal to determine its
221    // SVal.
222    if (X.isUndef() && cast<UndefinedVal>(X).getData())
223      EBMapRef = EBMapRef.add(BlkExpr, X);
224  }
225
226  // Go through he deferred locations and add them to the new environment if
227  // the correspond Stmt* is in the map as well.
228  for (SmallVectorImpl<std::pair<EnvironmentEntry, SVal> >::iterator
229      I = deferredLocations.begin(), E = deferredLocations.end(); I != E; ++I) {
230    const EnvironmentEntry &En = I->first;
231    const Stmt *S = (Stmt*) (((uintptr_t) En.getStmt()) & (uintptr_t) ~0x1);
232    if (EBMapRef.lookup(EnvironmentEntry(S, En.getLocationContext())))
233      EBMapRef = EBMapRef.add(En, I->second);
234  }
235
236  NewEnv.ExprBindings = EBMapRef.asImmutableMap();
237  return NewEnv;
238}
239
240void Environment::print(raw_ostream &Out, const char *NL,
241                        const char *Sep) const {
242  printAux(Out, false, NL, Sep);
243  printAux(Out, true, NL, Sep);
244}
245
246void Environment::printAux(raw_ostream &Out, bool printLocations,
247                           const char *NL,
248                           const char *Sep) const{
249
250  bool isFirst = true;
251
252  for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
253    const EnvironmentEntry &En = I.getKey();
254    if (IsLocation(En)) {
255      if (!printLocations)
256        continue;
257    }
258    else {
259      if (printLocations)
260        continue;
261    }
262
263    if (isFirst) {
264      Out << NL << NL
265          << (printLocations ? "Load/Store locations:" : "Expressions:")
266          << NL;
267      isFirst = false;
268    } else {
269      Out << NL;
270    }
271
272    const Stmt *S = En.getStmt();
273    if (printLocations) {
274      S = (Stmt*) (((uintptr_t) S) & ((uintptr_t) ~0x1));
275    }
276
277    Out << " (" << (void*) En.getLocationContext() << ',' << (void*) S << ") ";
278    LangOptions LO; // FIXME.
279    S->printPretty(Out, 0, PrintingPolicy(LO));
280    Out << " : " << I.getData();
281  }
282}
283