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 #include "llvm/Support/raw_ostream.h"
20
21 using namespace clang;
22 using namespace ento;
23
ignoreTransparentExprs(const Expr * E)24 static const Expr *ignoreTransparentExprs(const Expr *E) {
25 E = E->IgnoreParens();
26
27 switch (E->getStmtClass()) {
28 case Stmt::OpaqueValueExprClass:
29 E = cast<OpaqueValueExpr>(E)->getSourceExpr();
30 break;
31 case Stmt::ExprWithCleanupsClass:
32 E = cast<ExprWithCleanups>(E)->getSubExpr();
33 break;
34 case Stmt::CXXBindTemporaryExprClass:
35 E = cast<CXXBindTemporaryExpr>(E)->getSubExpr();
36 break;
37 case Stmt::SubstNonTypeTemplateParmExprClass:
38 E = cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement();
39 break;
40 default:
41 // This is the base case: we can't look through more than we already have.
42 return E;
43 }
44
45 return ignoreTransparentExprs(E);
46 }
47
ignoreTransparentExprs(const Stmt * S)48 static const Stmt *ignoreTransparentExprs(const Stmt *S) {
49 if (const Expr *E = dyn_cast<Expr>(S))
50 return ignoreTransparentExprs(E);
51 return S;
52 }
53
EnvironmentEntry(const Stmt * S,const LocationContext * L)54 EnvironmentEntry::EnvironmentEntry(const Stmt *S, const LocationContext *L)
55 : std::pair<const Stmt *,
56 const StackFrameContext *>(ignoreTransparentExprs(S),
57 L ? L->getCurrentStackFrame()
58 : nullptr) {}
59
lookupExpr(const EnvironmentEntry & E) const60 SVal Environment::lookupExpr(const EnvironmentEntry &E) const {
61 const SVal* X = ExprBindings.lookup(E);
62 if (X) {
63 SVal V = *X;
64 return V;
65 }
66 return UnknownVal();
67 }
68
getSVal(const EnvironmentEntry & Entry,SValBuilder & svalBuilder) const69 SVal Environment::getSVal(const EnvironmentEntry &Entry,
70 SValBuilder& svalBuilder) const {
71 const Stmt *S = Entry.getStmt();
72 const LocationContext *LCtx = Entry.getLocationContext();
73
74 switch (S->getStmtClass()) {
75 case Stmt::CXXBindTemporaryExprClass:
76 case Stmt::ExprWithCleanupsClass:
77 case Stmt::GenericSelectionExprClass:
78 case Stmt::OpaqueValueExprClass:
79 case Stmt::ParenExprClass:
80 case Stmt::SubstNonTypeTemplateParmExprClass:
81 llvm_unreachable("Should have been handled by ignoreTransparentExprs");
82
83 case Stmt::AddrLabelExprClass:
84 case Stmt::CharacterLiteralClass:
85 case Stmt::CXXBoolLiteralExprClass:
86 case Stmt::CXXScalarValueInitExprClass:
87 case Stmt::ImplicitValueInitExprClass:
88 case Stmt::IntegerLiteralClass:
89 case Stmt::ObjCBoolLiteralExprClass:
90 case Stmt::CXXNullPtrLiteralExprClass:
91 case Stmt::ObjCStringLiteralClass:
92 case Stmt::StringLiteralClass:
93 // Known constants; defer to SValBuilder.
94 return svalBuilder.getConstantVal(cast<Expr>(S)).getValue();
95
96 case Stmt::ReturnStmtClass: {
97 const ReturnStmt *RS = cast<ReturnStmt>(S);
98 if (const Expr *RE = RS->getRetValue())
99 return getSVal(EnvironmentEntry(RE, LCtx), svalBuilder);
100 return UndefinedVal();
101 }
102
103 // Handle all other Stmt* using a lookup.
104 default:
105 return lookupExpr(EnvironmentEntry(S, LCtx));
106 }
107 }
108
bindExpr(Environment Env,const EnvironmentEntry & E,SVal V,bool Invalidate)109 Environment EnvironmentManager::bindExpr(Environment Env,
110 const EnvironmentEntry &E,
111 SVal V,
112 bool Invalidate) {
113 if (V.isUnknown()) {
114 if (Invalidate)
115 return Environment(F.remove(Env.ExprBindings, E));
116 else
117 return Env;
118 }
119 return Environment(F.add(Env.ExprBindings, E, V));
120 }
121
122 namespace {
123 class MarkLiveCallback : public SymbolVisitor {
124 SymbolReaper &SymReaper;
125 public:
MarkLiveCallback(SymbolReaper & symreaper)126 MarkLiveCallback(SymbolReaper &symreaper) : SymReaper(symreaper) {}
VisitSymbol(SymbolRef sym)127 bool VisitSymbol(SymbolRef sym) override {
128 SymReaper.markLive(sym);
129 return true;
130 }
VisitMemRegion(const MemRegion * R)131 bool VisitMemRegion(const MemRegion *R) override {
132 SymReaper.markLive(R);
133 return true;
134 }
135 };
136 } // end anonymous namespace
137
138 // removeDeadBindings:
139 // - Remove subexpression bindings.
140 // - Remove dead block expression bindings.
141 // - Keep live block expression bindings:
142 // - Mark their reachable symbols live in SymbolReaper,
143 // see ScanReachableSymbols.
144 // - Mark the region in DRoots if the binding is a loc::MemRegionVal.
145 Environment
removeDeadBindings(Environment Env,SymbolReaper & SymReaper,ProgramStateRef ST)146 EnvironmentManager::removeDeadBindings(Environment Env,
147 SymbolReaper &SymReaper,
148 ProgramStateRef ST) {
149
150 // We construct a new Environment object entirely, as this is cheaper than
151 // individually removing all the subexpression bindings (which will greatly
152 // outnumber block-level expression bindings).
153 Environment NewEnv = getInitialEnvironment();
154
155 MarkLiveCallback CB(SymReaper);
156 ScanReachableSymbols RSScaner(ST, CB);
157
158 llvm::ImmutableMapRef<EnvironmentEntry,SVal>
159 EBMapRef(NewEnv.ExprBindings.getRootWithoutRetain(),
160 F.getTreeFactory());
161
162 // Iterate over the block-expr bindings.
163 for (Environment::iterator I = Env.begin(), E = Env.end();
164 I != E; ++I) {
165
166 const EnvironmentEntry &BlkExpr = I.getKey();
167 const SVal &X = I.getData();
168
169 if (SymReaper.isLive(BlkExpr.getStmt(), BlkExpr.getLocationContext())) {
170 // Copy the binding to the new map.
171 EBMapRef = EBMapRef.add(BlkExpr, X);
172
173 // If the block expr's value is a memory region, then mark that region.
174 if (Optional<loc::MemRegionVal> R = X.getAs<loc::MemRegionVal>())
175 SymReaper.markLive(R->getRegion());
176
177 // Mark all symbols in the block expr's value live.
178 RSScaner.scan(X);
179 continue;
180 } else {
181 SymExpr::symbol_iterator SI = X.symbol_begin(), SE = X.symbol_end();
182 for (; SI != SE; ++SI)
183 SymReaper.maybeDead(*SI);
184 }
185 }
186
187 NewEnv.ExprBindings = EBMapRef.asImmutableMap();
188 return NewEnv;
189 }
190
print(raw_ostream & Out,const char * NL,const char * Sep) const191 void Environment::print(raw_ostream &Out, const char *NL,
192 const char *Sep) const {
193 bool isFirst = true;
194
195 for (Environment::iterator I = begin(), E = end(); I != E; ++I) {
196 const EnvironmentEntry &En = I.getKey();
197
198 if (isFirst) {
199 Out << NL << NL
200 << "Expressions:"
201 << NL;
202 isFirst = false;
203 } else {
204 Out << NL;
205 }
206
207 const Stmt *S = En.getStmt();
208 assert(S != nullptr && "Expected non-null Stmt");
209
210 Out << " (" << (const void*) En.getLocationContext() << ','
211 << (const void*) S << ") ";
212 LangOptions LO; // FIXME.
213 S->printPretty(Out, nullptr, PrintingPolicy(LO));
214 Out << " : " << I.getData();
215 }
216 }
217