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 
20 using namespace clang;
21 using namespace ento;
22 
23 SVal 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 
32 SVal 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 
133 Environment 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 
146 static 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 
152 Environment 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 
159 namespace {
160 class MarkLiveCallback : public SymbolVisitor {
161   SymbolReaper &SymReaper;
162 public:
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.
178 static 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.
190 Environment
191 EnvironmentManager::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 
255 void 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 
261 void 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 << " (" << (const void*) En.getLocationContext() << ','
293       << (const void*) S << ") ";
294     LangOptions LO; // FIXME.
295     S->printPretty(Out, 0, PrintingPolicy(LO));
296     Out << " : " << I.getData();
297   }
298 }
299