clang 10.0.0git

ObjCSelfInitChecker.cpp
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1 //== ObjCSelfInitChecker.cpp - Checker for 'self' initialization -*- C++ -*--=//
2 //
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
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This defines ObjCSelfInitChecker, a builtin check that checks for uses of
10 // 'self' before proper initialization.
11 //
12 //===----------------------------------------------------------------------===//
13
14 // This checks initialization methods to verify that they assign 'self' to the
15 // result of an initialization call (e.g. [super init], or [self initWith..])
16 // before using 'self' or any instance variable.
17 //
18 // To perform the required checking, values are tagged with flags that indicate
19 // 1) if the object is the one pointed to by 'self', and 2) if the object
20 // is the result of an initializer (e.g. [super init]).
21 //
22 // Uses of an object that is true for 1) but not 2) trigger a diagnostic.
23 // The uses that are currently checked are:
24 // - Using instance variables.
25 // - Returning the object.
26 //
27 // Note that we don't check for an invalid 'self' that is the receiver of an
28 // obj-c message expression to cut down false positives where logging functions
29 // get information from self (like its class) or doing "invalidation" on self
30 // when the initialization fails.
31 //
32 // Because the object that 'self' points to gets invalidated when a call
33 // receives a reference to 'self', the checker keeps track and passes the flags
34 // for 1) and 2) to the new object that 'self' points to after the call.
35 //
36 //===----------------------------------------------------------------------===//
37
38 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
39 #include "clang/AST/ParentMap.h"
40 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
41 #include "clang/StaticAnalyzer/Core/Checker.h"
42 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
43 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
44 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
45 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
46 #include "llvm/Support/raw_ostream.h"
47
48 using namespace clang;
49 using namespace ento;
50
51 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND);
52 static bool isInitializationMethod(const ObjCMethodDecl *MD);
53 static bool isInitMessage(const ObjCMethodCall &Msg);
54 static bool isSelfVar(SVal location, CheckerContext &C);
55
56 namespace {
57 class ObjCSelfInitChecker : public Checker< check::PostObjCMessage,
58 check::PostStmt<ObjCIvarRefExpr>,
59 check::PreStmt<ReturnStmt>,
60 check::PreCall,
61 check::PostCall,
62 check::Location,
63 check::Bind > {
64 mutable std::unique_ptr<BugType> BT;
65
66 void checkForInvalidSelf(const Expr *E, CheckerContext &C,
67 const char *errorStr) const;
68
69 public:
70 ObjCSelfInitChecker() {}
71 void checkPostObjCMessage(const ObjCMethodCall &Msg, CheckerContext &C) const;
72 void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const;
73 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
74 void checkLocation(SVal location, bool isLoad, const Stmt *S,
75 CheckerContext &C) const;
76 void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
77
78 void checkPreCall(const CallEvent &CE, CheckerContext &C) const;
79 void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
80
81 void printState(raw_ostream &Out, ProgramStateRef State,
82 const char *NL, const char *Sep) const override;
83 };
84 } // end anonymous namespace
85
86 namespace {
87 enum SelfFlagEnum {
88 /// No flag set.
89 SelfFlag_None = 0x0,
90 /// Value came from 'self'.
91 SelfFlag_Self = 0x1,
92 /// Value came from the result of an initializer (e.g. [super init]).
93 SelfFlag_InitRes = 0x2
94 };
95 }
96
97 REGISTER_MAP_WITH_PROGRAMSTATE(SelfFlag, SymbolRef, unsigned)
98 REGISTER_TRAIT_WITH_PROGRAMSTATE(CalledInit, bool)
99
100 /// A call receiving a reference to 'self' invalidates the object that
101 /// 'self' contains. This keeps the "self flags" assigned to the 'self'
102 /// object before the call so we can assign them to the new object that 'self'
103 /// points to after the call.
104 REGISTER_TRAIT_WITH_PROGRAMSTATE(PreCallSelfFlags, unsigned)
105
106 static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state) {
107 if (SymbolRef sym = val.getAsSymbol())
108 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym))
109 return (SelfFlagEnum)*attachedFlags;
110 return SelfFlag_None;
111 }
112
113 static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) {
114 return getSelfFlags(val, C.getState());
115 }
116
117 static void addSelfFlag(ProgramStateRef state, SVal val,
118 SelfFlagEnum flag, CheckerContext &C) {
119 // We tag the symbol that the SVal wraps.
120 if (SymbolRef sym = val.getAsSymbol()) {
121 state = state->set<SelfFlag>(sym, getSelfFlags(val, state) | flag);
122 C.addTransition(state);
123 }
124 }
125
126 static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) {
127 return getSelfFlags(val, C) & flag;
128 }
129
130 /// Returns true of the value of the expression is the object that 'self'
131 /// points to and is an object that did not come from the result of calling
132 /// an initializer.
133 static bool isInvalidSelf(const Expr *E, CheckerContext &C) {
134 SVal exprVal = C.getSVal(E);
135 if (!hasSelfFlag(exprVal, SelfFlag_Self, C))
136 return false; // value did not come from 'self'.
137 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C))
138 return false; // 'self' is properly initialized.
139
140 return true;
141 }
142
143 void ObjCSelfInitChecker::checkForInvalidSelf(const Expr *E, CheckerContext &C,
144 const char *errorStr) const {
145 if (!E)
146 return;
147
148 if (!C.getState()->get<CalledInit>())
149 return;
150
151 if (!isInvalidSelf(E, C))
152 return;
153
154 // Generate an error node.
155 ExplodedNode *N = C.generateErrorNode();
156 if (!N)
157 return;
158
159 if (!BT)
160 BT.reset(new BugType(this, "Missing \"self = [(super or self) init...]\"",
161 categories::CoreFoundationObjectiveC));
162 C.emitReport(std::make_unique<PathSensitiveBugReport>(*BT, errorStr, N));
163 }
164
165 void ObjCSelfInitChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
166 CheckerContext &C) const {
167 // When encountering a message that does initialization (init rule),
168 // tag the return value so that we know later on that if self has this value
169 // then it is properly initialized.
170
171 // FIXME: A callback should disable checkers at the start of functions.
172 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
173 C.getCurrentAnalysisDeclContext()->getDecl())))
174 return;
175
176 if (isInitMessage(Msg)) {
177 // Tag the return value as the result of an initializer.
178 ProgramStateRef state = C.getState();
179
180 // FIXME this really should be context sensitive, where we record
181 // the current stack frame (for IPA). Also, we need to clean this
182 // value out when we return from this method.
183 state = state->set<CalledInit>(true);
184
185 SVal V = C.getSVal(Msg.getOriginExpr());
186 addSelfFlag(state, V, SelfFlag_InitRes, C);
187 return;
188 }
189
190 // We don't check for an invalid 'self' in an obj-c message expression to cut
191 // down false positives where logging functions get information from self
192 // (like its class) or doing "invalidation" on self when the initialization
193 // fails.
194 }
195
196 void ObjCSelfInitChecker::checkPostStmt(const ObjCIvarRefExpr *E,
197 CheckerContext &C) const {
198 // FIXME: A callback should disable checkers at the start of functions.
199 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
200 C.getCurrentAnalysisDeclContext()->getDecl())))
201 return;
202
203 checkForInvalidSelf(
204 E->getBase(), C,
205 "Instance variable used while 'self' is not set to the result of "
206 "'[(super or self) init...]'");
207 }
208
209 void ObjCSelfInitChecker::checkPreStmt(const ReturnStmt *S,
210 CheckerContext &C) const {
211 // FIXME: A callback should disable checkers at the start of functions.
212 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
213 C.getCurrentAnalysisDeclContext()->getDecl())))
214 return;
215
216 checkForInvalidSelf(S->getRetValue(), C,
217 "Returning 'self' while it is not set to the result of "
218 "'[(super or self) init...]'");
219 }
220
221 // When a call receives a reference to 'self', [Pre/Post]Call pass
222 // the SelfFlags from the object 'self' points to before the call to the new
223 // object after the call. This is to avoid invalidation of 'self' by logging
224 // functions.
225 // Another common pattern in classes with multiple initializers is to put the
226 // subclass's common initialization bits into a static function that receives
227 // the value of 'self', e.g:
228 // @code
229 // if (!(self = [super init]))
230 // return nil;
231 // if (!(self = _commonInit(self)))
232 // return nil;
233 // @endcode
234 // Until we can use inter-procedural analysis, in such a call, transfer the
235 // SelfFlags to the result of the call.
236
237 void ObjCSelfInitChecker::checkPreCall(const CallEvent &CE,
238 CheckerContext &C) const {
239 // FIXME: A callback should disable checkers at the start of functions.
240 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
241 C.getCurrentAnalysisDeclContext()->getDecl())))
242 return;
243
244 ProgramStateRef state = C.getState();
245 unsigned NumArgs = CE.getNumArgs();
246 // If we passed 'self' as and argument to the call, record it in the state
247 // to be propagated after the call.
248 // Note, we could have just given up, but try to be more optimistic here and
249 // assume that the functions are going to continue initialization or will not
250 // modify self.
251 for (unsigned i = 0; i < NumArgs; ++i) {
252 SVal argV = CE.getArgSVal(i);
253 if (isSelfVar(argV, C)) {
254 unsigned selfFlags = getSelfFlags(state->getSVal(argV.castAs<Loc>()), C);
255 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
256 return;
257 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
258 unsigned selfFlags = getSelfFlags(argV, C);
259 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
260 return;
261 }
262 }
263 }
264
265 void ObjCSelfInitChecker::checkPostCall(const CallEvent &CE,
266 CheckerContext &C) const {
267 // FIXME: A callback should disable checkers at the start of functions.
268 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
269 C.getCurrentAnalysisDeclContext()->getDecl())))
270 return;
271
272 ProgramStateRef state = C.getState();
273 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
274 if (!prevFlags)
275 return;
276 state = state->remove<PreCallSelfFlags>();
277
278 unsigned NumArgs = CE.getNumArgs();
279 for (unsigned i = 0; i < NumArgs; ++i) {
280 SVal argV = CE.getArgSVal(i);
281 if (isSelfVar(argV, C)) {
282 // If the address of 'self' is being passed to the call, assume that the
283 // 'self' after the call will have the same flags.
284 // EX: log(&self)
285 addSelfFlag(state, state->getSVal(argV.castAs<Loc>()), prevFlags, C);
286 return;
287 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
288 // If 'self' is passed to the call by value, assume that the function
289 // returns 'self'. So assign the flags, which were set on 'self' to the
290 // return value.
291 // EX: self = performMoreInitialization(self)
292 addSelfFlag(state, CE.getReturnValue(), prevFlags, C);
293 return;
294 }
295 }
296
297 C.addTransition(state);
298 }
299
300 void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad,
301 const Stmt *S,
302 CheckerContext &C) const {
303 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
304 C.getCurrentAnalysisDeclContext()->getDecl())))
305 return;
306
307 // Tag the result of a load from 'self' so that we can easily know that the
308 // value is the object that 'self' points to.
309 ProgramStateRef state = C.getState();
310 if (isSelfVar(location, C))
311 addSelfFlag(state, state->getSVal(location.castAs<Loc>()), SelfFlag_Self,
312 C);
313 }
314
315
316 void ObjCSelfInitChecker::checkBind(SVal loc, SVal val, const Stmt *S,
317 CheckerContext &C) const {
318 // Allow assignment of anything to self. Self is a local variable in the
319 // initializer, so it is legal to assign anything to it, like results of
320 // static functions/method calls. After self is assigned something we cannot
321 // reason about, stop enforcing the rules.
322 // (Only continue checking if the assigned value should be treated as self.)
323 if ((isSelfVar(loc, C)) &&
324 !hasSelfFlag(val, SelfFlag_InitRes, C) &&
325 !hasSelfFlag(val, SelfFlag_Self, C) &&
326 !isSelfVar(val, C)) {
327
328 // Stop tracking the checker-specific state in the state.
329 ProgramStateRef State = C.getState();
330 State = State->remove<CalledInit>();
331 if (SymbolRef sym = loc.getAsSymbol())
332 State = State->remove<SelfFlag>(sym);
333 C.addTransition(State);
334 }
335 }
336
337 void ObjCSelfInitChecker::printState(raw_ostream &Out, ProgramStateRef State,
338 const char *NL, const char *Sep) const {
339 SelfFlagTy FlagMap = State->get<SelfFlag>();
340 bool DidCallInit = State->get<CalledInit>();
341 SelfFlagEnum PreCallFlags = (SelfFlagEnum)State->get<PreCallSelfFlags>();
342
343 if (FlagMap.isEmpty() && !DidCallInit && !PreCallFlags)
344 return;
345
346 Out << Sep << NL << *this << " :" << NL;
347
348 if (DidCallInit)
349 Out << " An init method has been called." << NL;
350
351 if (PreCallFlags != SelfFlag_None) {
352 if (PreCallFlags & SelfFlag_Self) {
353 Out << " An argument of the current call came from the 'self' variable."
354 << NL;
355 }
356 if (PreCallFlags & SelfFlag_InitRes) {
357 Out << " An argument of the current call came from an init method."
358 << NL;
359 }
360 }
361
362 Out << NL;
363 for (SelfFlagTy::iterator I = FlagMap.begin(), E = FlagMap.end();
364 I != E; ++I) {
365 Out << I->first << " : ";
366
367 if (I->second == SelfFlag_None)
368 Out << "none";
369
370 if (I->second & SelfFlag_Self)
371 Out << "self variable";
372
373 if (I->second & SelfFlag_InitRes) {
374 if (I->second != SelfFlag_InitRes)
375 Out << " | ";
376 Out << "result of init method";
377 }
378
379 Out << NL;
380 }
381 }
382
383
384 // FIXME: A callback should disable checkers at the start of functions.
385 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) {
386 if (!ND)
387 return false;
388
389 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND);
390 if (!MD)
391 return false;
392 if (!isInitializationMethod(MD))
393 return false;
394
395 // self = [super init] applies only to NSObject subclasses.
396 // For instance, NSProxy doesn't implement -init.
397 ASTContext &Ctx = MD->getASTContext();
398 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
399 ObjCInterfaceDecl *ID = MD->getClassInterface()->getSuperClass();
400 for ( ; ID ; ID = ID->getSuperClass()) {
401 IdentifierInfo *II = ID->getIdentifier();
402
403 if (II == NSObjectII)
404 break;
405 }
406 return ID != nullptr;
407 }
408
409 /// Returns true if the location is 'self'.
410 static bool isSelfVar(SVal location, CheckerContext &C) {
411 AnalysisDeclContext *analCtx = C.getCurrentAnalysisDeclContext();
412 if (!analCtx->getSelfDecl())
413 return false;
414 if (!location.getAs<loc::MemRegionVal>())
415 return false;
416
417 loc::MemRegionVal MRV = location.castAs<loc::MemRegionVal>();
418 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts()))
419 return (DR->getDecl() == analCtx->getSelfDecl());
420
421 return false;
422 }
423
424 static bool isInitializationMethod(const ObjCMethodDecl *MD) {
425 return MD->getMethodFamily() == OMF_init;
426 }
427
428 static bool isInitMessage(const ObjCMethodCall &Call) {
429 return Call.getMethodFamily() == OMF_init;
430 }
431
432 //===----------------------------------------------------------------------===//
433 // Registration.
434 //===----------------------------------------------------------------------===//
435
436 void ento::registerObjCSelfInitChecker(CheckerManager &mgr) {
437 mgr.registerChecker<ObjCSelfInitChecker>();
438 }
439
440 bool ento::shouldRegisterObjCSelfInitChecker(const LangOptions &LO) {
441 return true;
442 }
clang::Builtin::ID
ID
Definition: Builtins.h:46
ento
clang::ento::categories::CoreFoundationObjectiveC
const char *const CoreFoundationObjectiveC
Definition: CommonBugCategories.cpp:14
SelfFlagEnum
SelfFlagEnum
Definition: ObjCSelfInitChecker.cpp:87
clang::ObjCMethodDecl::getClassInterface
ObjCInterfaceDecl * getClassInterface()
Definition: DeclObjC.cpp:1155
clang::Stmt
Stmt - This represents one statement.
Definition: Stmt.h:66
clang::ento::ProgramStateRef
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Definition: ProgramState_Fwd.h:37
BugType.h
clang::ObjCMethodDecl
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:138
clang::NamedDecl::getIdentifier
IdentifierInfo * getIdentifier() const
Get the identifier that names this declaration, if there is one.
Definition: Decl.h:244
clang::IdentifierInfo
One of these records is kept for each identifier that is lexed.
Definition: IdentifierTable.h:57
isInvalidSelf
static bool isInvalidSelf(const Expr *E, CheckerContext &C)
Returns true of the value of the expression is the object that &#39;self&#39; points to and is an object that...
Definition: ObjCSelfInitChecker.cpp:133
clang::ento::SymbolRef
const SymExpr * SymbolRef
Definition: SymExpr.h:110
clang::ASTContext
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:168
State
LineState State
Definition: UnwrappedLineFormatter.cpp:932
clang::AnalysisDeclContext
AnalysisDeclContext contains the context data for the function or method under analysis.
Definition: AnalysisDeclContext.h:69
Checker.h
CheckerManager.h
clang::LangOptions
Keeps track of the various options that can be enabled, which controls the dialect of C or C++ that i...
Definition: LangOptions.h:53
clang::CodeGen::state
i32 captured_struct **param SharedsTy A type which contains references the shared variables *param Shareds Context with the list of shared variables from the p *TaskFunction *param Data Additional data for task generation like final * state
Definition: CGOpenMPRuntime.h:802
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IdentifierTable & Idents
Definition: ASTContext.h:580
isInitMessage
static bool isInitMessage(const ObjCMethodCall &Msg)
Definition: ObjCSelfInitChecker.cpp:428
isInitializationMethod
static bool isInitializationMethod(const ObjCMethodDecl *MD)
Definition: ObjCSelfInitChecker.cpp:424
clang::ObjCMethodDecl::getMethodFamily
ObjCMethodFamily getMethodFamily() const
Determines the family of this method.
Definition: DeclObjC.cpp:997
clang::ObjCMethodCall
Represents any expression that calls an Objective-C method.
Definition: CallEvent.h:938
addSelfFlag
static void addSelfFlag(ProgramStateRef state, SVal val, SelfFlagEnum flag, CheckerContext &C)
Definition: ObjCSelfInitChecker.cpp:117
getSelfFlags
static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state)
A call receiving a reference to &#39;self&#39; invalidates the object that &#39;self&#39; contains.
Definition: ObjCSelfInitChecker.cpp:106
clang::ObjCInterfaceDecl
Represents an ObjC class declaration.
Definition: DeclObjC.h:1186
clang::Expr
This represents one expression.
Definition: Expr.h:108
ParentMap.h
V
#define V(N, I)
Definition: ASTContext.h:2941
shouldRunOnFunctionOrMethod
static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND)
Definition: ObjCSelfInitChecker.cpp:385
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ObjCInterfaceDecl * getSuperClass() const
Definition: DeclObjC.cpp:337
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ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:2636
BuiltinCheckerRegistration.h
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const ImplicitParamDecl * getSelfDecl() const
Return the ImplicitParamDecl* associated with &#39;self&#39; if this AnalysisDeclContext wraps an ObjCMethodD...
Definition: AnalysisDeclContext.cpp:148
hasSelfFlag
static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C)
Definition: ObjCSelfInitChecker.cpp:126
REGISTER_TRAIT_WITH_PROGRAMSTATE
#define REGISTER_TRAIT_WITH_PROGRAMSTATE(Name, Type)
Declares a program state trait for type Type called Name, and introduce a type named NameTy...
Definition: ProgramStateTrait.h:33
clang::IdentifierTable::get
IdentifierInfo & get(StringRef Name)
Return the identifier token info for the specified named identifier.
Definition: IdentifierTable.h:529
clang::ReturnStmt::getRetValue
Expr * getRetValue()
Definition: Stmt.h:2669
REGISTER_MAP_WITH_PROGRAMSTATE
#define REGISTER_MAP_WITH_PROGRAMSTATE(Name, Key, Value)
Declares an immutable map of type NameTy, suitable for placement into the ProgramState.
Definition: ProgramStateTrait.h:84
clang::Decl::getASTContext
ASTContext & getASTContext() const LLVM_READONLY
Definition: DeclBase.cpp:377
isSelfVar
static bool isSelfVar(SVal location, CheckerContext &C)
Returns true if the location is &#39;self&#39;.
Definition: ObjCSelfInitChecker.cpp:410
clang::ObjCMethodCall::getOriginExpr
virtual const ObjCMessageExpr * getOriginExpr() const
Definition: CallEvent.h:962
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:21
clang::ObjCMethodCall::getMethodFamily
ObjCMethodFamily getMethodFamily() const
Definition: CallEvent.h:982
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const Expr * getBase() const
Definition: ExprObjC.h:580
clang::ObjCIvarRefExpr
ObjCIvarRefExpr - A reference to an ObjC instance variable.
Definition: ExprObjC.h:546
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Definition: IdentifierTable.h:633
clang::NamedDecl
This represents a decl that may have a name.
Definition: Decl.h:223
ProgramStateTrait.h
CallEvent.h
CallEvent
CheckerContext.h