1//== TrustNonnullChecker.cpp --------- API nullability modeling -*- C++ -*--==//
2//
| 1//== TrustNonnullChecker.cpp --------- API nullability modeling -*- C++ -*--==//
2//
|
3// The LLVM Compiler Infrastructure
| 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
4//
| 6//
|
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
| |
8//===----------------------------------------------------------------------===//
9//
10// This checker adds nullability-related assumptions:
11//
12// 1. Methods annotated with _Nonnull
13// which come from system headers actually return a non-null pointer.
14//
15// 2. NSDictionary key is non-null after the keyword subscript operation
16// on read if and only if the resulting expression is non-null.
17//
18// 3. NSMutableDictionary index is non-null after a write operation.
19//
20//===----------------------------------------------------------------------===//
21
22#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
23#include "clang/Analysis/SelectorExtras.h"
24#include "clang/StaticAnalyzer/Core/Checker.h"
25#include "clang/StaticAnalyzer/Core/CheckerManager.h"
26#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
27#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h"
28#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
29
30using namespace clang;
31using namespace ento;
32
33/// Records implications between symbols.
34/// The semantics is:
35/// (antecedent != 0) => (consequent != 0)
36/// These implications are then read during the evaluation of the assumption,
37/// and the appropriate antecedents are applied.
38REGISTER_MAP_WITH_PROGRAMSTATE(NonNullImplicationMap, SymbolRef, SymbolRef)
39
40/// The semantics is:
41/// (antecedent == 0) => (consequent == 0)
42REGISTER_MAP_WITH_PROGRAMSTATE(NullImplicationMap, SymbolRef, SymbolRef)
43
44namespace {
45
46class TrustNonnullChecker : public Checker<check::PostCall,
47 check::PostObjCMessage,
48 check::DeadSymbols,
49 eval::Assume> {
50 // Do not try to iterate over symbols with higher complexity.
51 static unsigned constexpr ComplexityThreshold = 10;
52 Selector ObjectForKeyedSubscriptSel;
53 Selector ObjectForKeySel;
54 Selector SetObjectForKeyedSubscriptSel;
55 Selector SetObjectForKeySel;
56
57public:
58 TrustNonnullChecker(ASTContext &Ctx)
59 : ObjectForKeyedSubscriptSel(
60 getKeywordSelector(Ctx, "objectForKeyedSubscript")),
61 ObjectForKeySel(getKeywordSelector(Ctx, "objectForKey")),
62 SetObjectForKeyedSubscriptSel(
63 getKeywordSelector(Ctx, "setObject", "forKeyedSubscript")),
64 SetObjectForKeySel(getKeywordSelector(Ctx, "setObject", "forKey")) {}
65
66 ProgramStateRef evalAssume(ProgramStateRef State,
67 SVal Cond,
68 bool Assumption) const {
69 const SymbolRef CondS = Cond.getAsSymbol();
70 if (!CondS || CondS->computeComplexity() > ComplexityThreshold)
71 return State;
72
73 for (auto B=CondS->symbol_begin(), E=CondS->symbol_end(); B != E; ++B) {
74 const SymbolRef Antecedent = *B;
75 State = addImplication(Antecedent, State, true);
76 State = addImplication(Antecedent, State, false);
77 }
78
79 return State;
80 }
81
82 void checkPostCall(const CallEvent &Call, CheckerContext &C) const {
83 // Only trust annotations for system headers for non-protocols.
84 if (!Call.isInSystemHeader())
85 return;
86
87 ProgramStateRef State = C.getState();
88
89 if (isNonNullPtr(Call, C))
90 if (auto L = Call.getReturnValue().getAs<Loc>())
| 7//===----------------------------------------------------------------------===//
8//
9// This checker adds nullability-related assumptions:
10//
11// 1. Methods annotated with _Nonnull
12// which come from system headers actually return a non-null pointer.
13//
14// 2. NSDictionary key is non-null after the keyword subscript operation
15// on read if and only if the resulting expression is non-null.
16//
17// 3. NSMutableDictionary index is non-null after a write operation.
18//
19//===----------------------------------------------------------------------===//
20
21#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
22#include "clang/Analysis/SelectorExtras.h"
23#include "clang/StaticAnalyzer/Core/Checker.h"
24#include "clang/StaticAnalyzer/Core/CheckerManager.h"
25#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
26#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerHelpers.h"
27#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
28
29using namespace clang;
30using namespace ento;
31
32/// Records implications between symbols.
33/// The semantics is:
34/// (antecedent != 0) => (consequent != 0)
35/// These implications are then read during the evaluation of the assumption,
36/// and the appropriate antecedents are applied.
37REGISTER_MAP_WITH_PROGRAMSTATE(NonNullImplicationMap, SymbolRef, SymbolRef)
38
39/// The semantics is:
40/// (antecedent == 0) => (consequent == 0)
41REGISTER_MAP_WITH_PROGRAMSTATE(NullImplicationMap, SymbolRef, SymbolRef)
42
43namespace {
44
45class TrustNonnullChecker : public Checker<check::PostCall,
46 check::PostObjCMessage,
47 check::DeadSymbols,
48 eval::Assume> {
49 // Do not try to iterate over symbols with higher complexity.
50 static unsigned constexpr ComplexityThreshold = 10;
51 Selector ObjectForKeyedSubscriptSel;
52 Selector ObjectForKeySel;
53 Selector SetObjectForKeyedSubscriptSel;
54 Selector SetObjectForKeySel;
55
56public:
57 TrustNonnullChecker(ASTContext &Ctx)
58 : ObjectForKeyedSubscriptSel(
59 getKeywordSelector(Ctx, "objectForKeyedSubscript")),
60 ObjectForKeySel(getKeywordSelector(Ctx, "objectForKey")),
61 SetObjectForKeyedSubscriptSel(
62 getKeywordSelector(Ctx, "setObject", "forKeyedSubscript")),
63 SetObjectForKeySel(getKeywordSelector(Ctx, "setObject", "forKey")) {}
64
65 ProgramStateRef evalAssume(ProgramStateRef State,
66 SVal Cond,
67 bool Assumption) const {
68 const SymbolRef CondS = Cond.getAsSymbol();
69 if (!CondS || CondS->computeComplexity() > ComplexityThreshold)
70 return State;
71
72 for (auto B=CondS->symbol_begin(), E=CondS->symbol_end(); B != E; ++B) {
73 const SymbolRef Antecedent = *B;
74 State = addImplication(Antecedent, State, true);
75 State = addImplication(Antecedent, State, false);
76 }
77
78 return State;
79 }
80
81 void checkPostCall(const CallEvent &Call, CheckerContext &C) const {
82 // Only trust annotations for system headers for non-protocols.
83 if (!Call.isInSystemHeader())
84 return;
85
86 ProgramStateRef State = C.getState();
87
88 if (isNonNullPtr(Call, C))
89 if (auto L = Call.getReturnValue().getAs<Loc>())
|
91 State = State->assume(*L, /*Assumption=*/true);
| 90 State = State->assume(*L, /*assumption=*/true);
|
92
93 C.addTransition(State);
94 }
95
96 void checkPostObjCMessage(const ObjCMethodCall &Msg,
97 CheckerContext &C) const {
98 const ObjCInterfaceDecl *ID = Msg.getReceiverInterface();
99 if (!ID)
100 return;
101
102 ProgramStateRef State = C.getState();
103
104 // Index to setter for NSMutableDictionary is assumed to be non-null,
105 // as an exception is thrown otherwise.
106 if (interfaceHasSuperclass(ID, "NSMutableDictionary") &&
107 (Msg.getSelector() == SetObjectForKeyedSubscriptSel ||
108 Msg.getSelector() == SetObjectForKeySel)) {
109 if (auto L = Msg.getArgSVal(1).getAs<Loc>())
| 91
92 C.addTransition(State);
93 }
94
95 void checkPostObjCMessage(const ObjCMethodCall &Msg,
96 CheckerContext &C) const {
97 const ObjCInterfaceDecl *ID = Msg.getReceiverInterface();
98 if (!ID)
99 return;
100
101 ProgramStateRef State = C.getState();
102
103 // Index to setter for NSMutableDictionary is assumed to be non-null,
104 // as an exception is thrown otherwise.
105 if (interfaceHasSuperclass(ID, "NSMutableDictionary") &&
106 (Msg.getSelector() == SetObjectForKeyedSubscriptSel ||
107 Msg.getSelector() == SetObjectForKeySel)) {
108 if (auto L = Msg.getArgSVal(1).getAs<Loc>())
|
110 State = State->assume(*L, /*Assumption=*/true);
| 109 State = State->assume(*L, /*assumption=*/true);
|
111 }
112
113 // Record an implication: index is non-null if the output is non-null.
114 if (interfaceHasSuperclass(ID, "NSDictionary") &&
115 (Msg.getSelector() == ObjectForKeyedSubscriptSel ||
116 Msg.getSelector() == ObjectForKeySel)) {
117 SymbolRef ArgS = Msg.getArgSVal(0).getAsSymbol();
118 SymbolRef RetS = Msg.getReturnValue().getAsSymbol();
119
120 if (ArgS && RetS) {
121 // Emulate an implication: the argument is non-null if
122 // the return value is non-null.
123 State = State->set<NonNullImplicationMap>(RetS, ArgS);
124
125 // Conversely, when the argument is null, the return value
126 // is definitely null.
127 State = State->set<NullImplicationMap>(ArgS, RetS);
128 }
129 }
130
131 C.addTransition(State);
132 }
133
134 void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const {
135 ProgramStateRef State = C.getState();
136
137 State = dropDeadFromGDM<NullImplicationMap>(SymReaper, State);
138 State = dropDeadFromGDM<NonNullImplicationMap>(SymReaper, State);
139
140 C.addTransition(State);
141 }
142
143private:
144
145 /// \returns State with GDM \p MapName where all dead symbols were
146 // removed.
147 template <typename MapName>
148 ProgramStateRef dropDeadFromGDM(SymbolReaper &SymReaper,
149 ProgramStateRef State) const {
150 for (const std::pair<SymbolRef, SymbolRef> &P : State->get<MapName>())
151 if (!SymReaper.isLive(P.first) || !SymReaper.isLive(P.second))
152 State = State->remove<MapName>(P.first);
153 return State;
154 }
155
156 /// \returns Whether we trust the result of the method call to be
157 /// a non-null pointer.
158 bool isNonNullPtr(const CallEvent &Call, CheckerContext &C) const {
159 QualType ExprRetType = Call.getResultType();
160 if (!ExprRetType->isAnyPointerType())
161 return false;
162
163 if (getNullabilityAnnotation(ExprRetType) == Nullability::Nonnull)
164 return true;
165
166 // The logic for ObjC instance method calls is more complicated,
167 // as the return value is nil when the receiver is nil.
168 if (!isa<ObjCMethodCall>(&Call))
169 return false;
170
171 const auto *MCall = cast<ObjCMethodCall>(&Call);
172 const ObjCMethodDecl *MD = MCall->getDecl();
173
174 // Distrust protocols.
175 if (isa<ObjCProtocolDecl>(MD->getDeclContext()))
176 return false;
177
178 QualType DeclRetType = MD->getReturnType();
179 if (getNullabilityAnnotation(DeclRetType) != Nullability::Nonnull)
180 return false;
181
182 // For class messages it is sufficient for the declaration to be
183 // annotated _Nonnull.
184 if (!MCall->isInstanceMessage())
185 return true;
186
187 // Alternatively, the analyzer could know that the receiver is not null.
188 SVal Receiver = MCall->getReceiverSVal();
189 ConditionTruthVal TV = C.getState()->isNonNull(Receiver);
190 if (TV.isConstrainedTrue())
191 return true;
192
193 return false;
194 }
195
196 /// \return Whether \p ID has a superclass by the name \p ClassName.
197 bool interfaceHasSuperclass(const ObjCInterfaceDecl *ID,
198 StringRef ClassName) const {
199 if (ID->getIdentifier()->getName() == ClassName)
200 return true;
201
202 if (const ObjCInterfaceDecl *Super = ID->getSuperClass())
203 return interfaceHasSuperclass(Super, ClassName);
204
205 return false;
206 }
207
208
209 /// \return a state with an optional implication added (if exists)
210 /// from a map of recorded implications.
211 /// If \p Negated is true, checks NullImplicationMap, and assumes
212 /// the negation of \p Antecedent.
213 /// Checks NonNullImplicationMap and assumes \p Antecedent otherwise.
214 ProgramStateRef addImplication(SymbolRef Antecedent,
215 ProgramStateRef InputState,
216 bool Negated) const {
217 if (!InputState)
218 return nullptr;
219 SValBuilder &SVB = InputState->getStateManager().getSValBuilder();
220 const SymbolRef *Consequent =
221 Negated ? InputState->get<NonNullImplicationMap>(Antecedent)
222 : InputState->get<NullImplicationMap>(Antecedent);
223 if (!Consequent)
224 return InputState;
225
226 SVal AntecedentV = SVB.makeSymbolVal(Antecedent);
227 ProgramStateRef State = InputState;
228
229 if ((Negated && InputState->isNonNull(AntecedentV).isConstrainedTrue())
230 || (!Negated && InputState->isNull(AntecedentV).isConstrainedTrue())) {
231 SVal ConsequentS = SVB.makeSymbolVal(*Consequent);
232 State = InputState->assume(ConsequentS.castAs<DefinedSVal>(), Negated);
233 if (!State)
234 return nullptr;
235
236 // Drop implications from the map.
237 if (Negated) {
238 State = State->remove<NonNullImplicationMap>(Antecedent);
239 State = State->remove<NullImplicationMap>(*Consequent);
240 } else {
241 State = State->remove<NullImplicationMap>(Antecedent);
242 State = State->remove<NonNullImplicationMap>(*Consequent);
243 }
244 }
245
246 return State;
247 }
248};
249
250} // end empty namespace
251
| 110 }
111
112 // Record an implication: index is non-null if the output is non-null.
113 if (interfaceHasSuperclass(ID, "NSDictionary") &&
114 (Msg.getSelector() == ObjectForKeyedSubscriptSel ||
115 Msg.getSelector() == ObjectForKeySel)) {
116 SymbolRef ArgS = Msg.getArgSVal(0).getAsSymbol();
117 SymbolRef RetS = Msg.getReturnValue().getAsSymbol();
118
119 if (ArgS && RetS) {
120 // Emulate an implication: the argument is non-null if
121 // the return value is non-null.
122 State = State->set<NonNullImplicationMap>(RetS, ArgS);
123
124 // Conversely, when the argument is null, the return value
125 // is definitely null.
126 State = State->set<NullImplicationMap>(ArgS, RetS);
127 }
128 }
129
130 C.addTransition(State);
131 }
132
133 void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const {
134 ProgramStateRef State = C.getState();
135
136 State = dropDeadFromGDM<NullImplicationMap>(SymReaper, State);
137 State = dropDeadFromGDM<NonNullImplicationMap>(SymReaper, State);
138
139 C.addTransition(State);
140 }
141
142private:
143
144 /// \returns State with GDM \p MapName where all dead symbols were
145 // removed.
146 template <typename MapName>
147 ProgramStateRef dropDeadFromGDM(SymbolReaper &SymReaper,
148 ProgramStateRef State) const {
149 for (const std::pair<SymbolRef, SymbolRef> &P : State->get<MapName>())
150 if (!SymReaper.isLive(P.first) || !SymReaper.isLive(P.second))
151 State = State->remove<MapName>(P.first);
152 return State;
153 }
154
155 /// \returns Whether we trust the result of the method call to be
156 /// a non-null pointer.
157 bool isNonNullPtr(const CallEvent &Call, CheckerContext &C) const {
158 QualType ExprRetType = Call.getResultType();
159 if (!ExprRetType->isAnyPointerType())
160 return false;
161
162 if (getNullabilityAnnotation(ExprRetType) == Nullability::Nonnull)
163 return true;
164
165 // The logic for ObjC instance method calls is more complicated,
166 // as the return value is nil when the receiver is nil.
167 if (!isa<ObjCMethodCall>(&Call))
168 return false;
169
170 const auto *MCall = cast<ObjCMethodCall>(&Call);
171 const ObjCMethodDecl *MD = MCall->getDecl();
172
173 // Distrust protocols.
174 if (isa<ObjCProtocolDecl>(MD->getDeclContext()))
175 return false;
176
177 QualType DeclRetType = MD->getReturnType();
178 if (getNullabilityAnnotation(DeclRetType) != Nullability::Nonnull)
179 return false;
180
181 // For class messages it is sufficient for the declaration to be
182 // annotated _Nonnull.
183 if (!MCall->isInstanceMessage())
184 return true;
185
186 // Alternatively, the analyzer could know that the receiver is not null.
187 SVal Receiver = MCall->getReceiverSVal();
188 ConditionTruthVal TV = C.getState()->isNonNull(Receiver);
189 if (TV.isConstrainedTrue())
190 return true;
191
192 return false;
193 }
194
195 /// \return Whether \p ID has a superclass by the name \p ClassName.
196 bool interfaceHasSuperclass(const ObjCInterfaceDecl *ID,
197 StringRef ClassName) const {
198 if (ID->getIdentifier()->getName() == ClassName)
199 return true;
200
201 if (const ObjCInterfaceDecl *Super = ID->getSuperClass())
202 return interfaceHasSuperclass(Super, ClassName);
203
204 return false;
205 }
206
207
208 /// \return a state with an optional implication added (if exists)
209 /// from a map of recorded implications.
210 /// If \p Negated is true, checks NullImplicationMap, and assumes
211 /// the negation of \p Antecedent.
212 /// Checks NonNullImplicationMap and assumes \p Antecedent otherwise.
213 ProgramStateRef addImplication(SymbolRef Antecedent,
214 ProgramStateRef InputState,
215 bool Negated) const {
216 if (!InputState)
217 return nullptr;
218 SValBuilder &SVB = InputState->getStateManager().getSValBuilder();
219 const SymbolRef *Consequent =
220 Negated ? InputState->get<NonNullImplicationMap>(Antecedent)
221 : InputState->get<NullImplicationMap>(Antecedent);
222 if (!Consequent)
223 return InputState;
224
225 SVal AntecedentV = SVB.makeSymbolVal(Antecedent);
226 ProgramStateRef State = InputState;
227
228 if ((Negated && InputState->isNonNull(AntecedentV).isConstrainedTrue())
229 || (!Negated && InputState->isNull(AntecedentV).isConstrainedTrue())) {
230 SVal ConsequentS = SVB.makeSymbolVal(*Consequent);
231 State = InputState->assume(ConsequentS.castAs<DefinedSVal>(), Negated);
232 if (!State)
233 return nullptr;
234
235 // Drop implications from the map.
236 if (Negated) {
237 State = State->remove<NonNullImplicationMap>(Antecedent);
238 State = State->remove<NullImplicationMap>(*Consequent);
239 } else {
240 State = State->remove<NullImplicationMap>(Antecedent);
241 State = State->remove<NonNullImplicationMap>(*Consequent);
242 }
243 }
244
245 return State;
246 }
247};
248
249} // end empty namespace
250
|
252
| |
253void ento::registerTrustNonnullChecker(CheckerManager &Mgr) {
254 Mgr.registerChecker<TrustNonnullChecker>(Mgr.getASTContext());
255}
| 251void ento::registerTrustNonnullChecker(CheckerManager &Mgr) {
252 Mgr.registerChecker<TrustNonnullChecker>(Mgr.getASTContext());
253}
|
| 254
255bool ento::shouldRegisterTrustNonnullChecker(const LangOptions &LO) {
256 return true;
257}
|
| |