clang 8.0.0

ObjCSelfInitChecker.cpp
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1 //== ObjCSelfInitChecker.cpp - Checker for 'self' initialization -*- 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 defines ObjCSelfInitChecker, a builtin check that checks for uses of
11 // 'self' before proper initialization.
12 //
13 //===----------------------------------------------------------------------===//
14
15 // This checks initialization methods to verify that they assign 'self' to the
16 // result of an initialization call (e.g. [super init], or [self initWith..])
17 // before using 'self' or any instance variable.
18 //
19 // To perform the required checking, values are tagged with flags that indicate
20 // 1) if the object is the one pointed to by 'self', and 2) if the object
21 // is the result of an initializer (e.g. [super init]).
22 //
23 // Uses of an object that is true for 1) but not 2) trigger a diagnostic.
24 // The uses that are currently checked are:
25 // - Using instance variables.
26 // - Returning the object.
27 //
28 // Note that we don't check for an invalid 'self' that is the receiver of an
29 // obj-c message expression to cut down false positives where logging functions
30 // get information from self (like its class) or doing "invalidation" on self
31 // when the initialization fails.
32 //
33 // Because the object that 'self' points to gets invalidated when a call
34 // receives a reference to 'self', the checker keeps track and passes the flags
35 // for 1) and 2) to the new object that 'self' points to after the call.
36 //
37 //===----------------------------------------------------------------------===//
38
39 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
40 #include "clang/AST/ParentMap.h"
41 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
42 #include "clang/StaticAnalyzer/Core/Checker.h"
43 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
44 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
45 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
46 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
47 #include "llvm/Support/raw_ostream.h"
48
49 using namespace clang;
50 using namespace ento;
51
52 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND);
53 static bool isInitializationMethod(const ObjCMethodDecl *MD);
54 static bool isInitMessage(const ObjCMethodCall &Msg);
55 static bool isSelfVar(SVal location, CheckerContext &C);
56
57 namespace {
58 class ObjCSelfInitChecker : public Checker< check::PostObjCMessage,
59 check::PostStmt<ObjCIvarRefExpr>,
60 check::PreStmt<ReturnStmt>,
61 check::PreCall,
62 check::PostCall,
63 check::Location,
64 check::Bind > {
65 mutable std::unique_ptr<BugType> BT;
66
67 void checkForInvalidSelf(const Expr *E, CheckerContext &C,
68 const char *errorStr) const;
69
70 public:
71 ObjCSelfInitChecker() {}
72 void checkPostObjCMessage(const ObjCMethodCall &Msg, CheckerContext &C) const;
73 void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const;
74 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
75 void checkLocation(SVal location, bool isLoad, const Stmt *S,
76 CheckerContext &C) const;
77 void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
78
79 void checkPreCall(const CallEvent &CE, CheckerContext &C) const;
80 void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
81
82 void printState(raw_ostream &Out, ProgramStateRef State,
83 const char *NL, const char *Sep) const override;
84 };
85 } // end anonymous namespace
86
87 namespace {
88 enum SelfFlagEnum {
89 /// No flag set.
90 SelfFlag_None = 0x0,
91 /// Value came from 'self'.
92 SelfFlag_Self = 0x1,
93 /// Value came from the result of an initializer (e.g. [super init]).
94 SelfFlag_InitRes = 0x2
95 };
96 }
97
98 REGISTER_MAP_WITH_PROGRAMSTATE(SelfFlag, SymbolRef, unsigned)
99 REGISTER_TRAIT_WITH_PROGRAMSTATE(CalledInit, bool)
100
101 /// A call receiving a reference to 'self' invalidates the object that
102 /// 'self' contains. This keeps the "self flags" assigned to the 'self'
103 /// object before the call so we can assign them to the new object that 'self'
104 /// points to after the call.
105 REGISTER_TRAIT_WITH_PROGRAMSTATE(PreCallSelfFlags, unsigned)
106
107 static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state) {
108 if (SymbolRef sym = val.getAsSymbol())
109 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym))
110 return (SelfFlagEnum)*attachedFlags;
111 return SelfFlag_None;
112 }
113
114 static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) {
115 return getSelfFlags(val, C.getState());
116 }
117
118 static void addSelfFlag(ProgramStateRef state, SVal val,
119 SelfFlagEnum flag, CheckerContext &C) {
120 // We tag the symbol that the SVal wraps.
121 if (SymbolRef sym = val.getAsSymbol()) {
122 state = state->set<SelfFlag>(sym, getSelfFlags(val, state) | flag);
123 C.addTransition(state);
124 }
125 }
126
127 static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) {
128 return getSelfFlags(val, C) & flag;
129 }
130
131 /// Returns true of the value of the expression is the object that 'self'
132 /// points to and is an object that did not come from the result of calling
133 /// an initializer.
134 static bool isInvalidSelf(const Expr *E, CheckerContext &C) {
135 SVal exprVal = C.getSVal(E);
136 if (!hasSelfFlag(exprVal, SelfFlag_Self, C))
137 return false; // value did not come from 'self'.
138 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C))
139 return false; // 'self' is properly initialized.
140
141 return true;
142 }
143
144 void ObjCSelfInitChecker::checkForInvalidSelf(const Expr *E, CheckerContext &C,
145 const char *errorStr) const {
146 if (!E)
147 return;
148
149 if (!C.getState()->get<CalledInit>())
150 return;
151
152 if (!isInvalidSelf(E, C))
153 return;
154
155 // Generate an error node.
156 ExplodedNode *N = C.generateErrorNode();
157 if (!N)
158 return;
159
160 if (!BT)
161 BT.reset(new BugType(this, "Missing \"self = [(super or self) init...]\"",
162 categories::CoreFoundationObjectiveC));
163 C.emitReport(llvm::make_unique<BugReport>(*BT, errorStr, N));
164 }
165
166 void ObjCSelfInitChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
167 CheckerContext &C) const {
168 // When encountering a message that does initialization (init rule),
169 // tag the return value so that we know later on that if self has this value
170 // then it is properly initialized.
171
172 // FIXME: A callback should disable checkers at the start of functions.
173 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
174 C.getCurrentAnalysisDeclContext()->getDecl())))
175 return;
176
177 if (isInitMessage(Msg)) {
178 // Tag the return value as the result of an initializer.
179 ProgramStateRef state = C.getState();
180
181 // FIXME this really should be context sensitive, where we record
182 // the current stack frame (for IPA). Also, we need to clean this
183 // value out when we return from this method.
184 state = state->set<CalledInit>(true);
185
186 SVal V = C.getSVal(Msg.getOriginExpr());
187 addSelfFlag(state, V, SelfFlag_InitRes, C);
188 return;
189 }
190
191 // We don't check for an invalid 'self' in an obj-c message expression to cut
192 // down false positives where logging functions get information from self
193 // (like its class) or doing "invalidation" on self when the initialization
194 // fails.
195 }
196
197 void ObjCSelfInitChecker::checkPostStmt(const ObjCIvarRefExpr *E,
198 CheckerContext &C) const {
199 // FIXME: A callback should disable checkers at the start of functions.
200 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
201 C.getCurrentAnalysisDeclContext()->getDecl())))
202 return;
203
204 checkForInvalidSelf(
205 E->getBase(), C,
206 "Instance variable used while 'self' is not set to the result of "
207 "'[(super or self) init...]'");
208 }
209
210 void ObjCSelfInitChecker::checkPreStmt(const ReturnStmt *S,
211 CheckerContext &C) const {
212 // FIXME: A callback should disable checkers at the start of functions.
213 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
214 C.getCurrentAnalysisDeclContext()->getDecl())))
215 return;
216
217 checkForInvalidSelf(S->getRetValue(), C,
218 "Returning 'self' while it is not set to the result of "
219 "'[(super or self) init...]'");
220 }
221
222 // When a call receives a reference to 'self', [Pre/Post]Call pass
223 // the SelfFlags from the object 'self' points to before the call to the new
224 // object after the call. This is to avoid invalidation of 'self' by logging
225 // functions.
226 // Another common pattern in classes with multiple initializers is to put the
227 // subclass's common initialization bits into a static function that receives
228 // the value of 'self', e.g:
229 // @code
230 // if (!(self = [super init]))
231 // return nil;
232 // if (!(self = _commonInit(self)))
233 // return nil;
234 // @endcode
235 // Until we can use inter-procedural analysis, in such a call, transfer the
236 // SelfFlags to the result of the call.
237
238 void ObjCSelfInitChecker::checkPreCall(const CallEvent &CE,
239 CheckerContext &C) const {
240 // FIXME: A callback should disable checkers at the start of functions.
241 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
242 C.getCurrentAnalysisDeclContext()->getDecl())))
243 return;
244
245 ProgramStateRef state = C.getState();
246 unsigned NumArgs = CE.getNumArgs();
247 // If we passed 'self' as and argument to the call, record it in the state
248 // to be propagated after the call.
249 // Note, we could have just given up, but try to be more optimistic here and
250 // assume that the functions are going to continue initialization or will not
251 // modify self.
252 for (unsigned i = 0; i < NumArgs; ++i) {
253 SVal argV = CE.getArgSVal(i);
254 if (isSelfVar(argV, C)) {
255 unsigned selfFlags = getSelfFlags(state->getSVal(argV.castAs<Loc>()), C);
256 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
257 return;
258 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
259 unsigned selfFlags = getSelfFlags(argV, C);
260 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
261 return;
262 }
263 }
264 }
265
266 void ObjCSelfInitChecker::checkPostCall(const CallEvent &CE,
267 CheckerContext &C) const {
268 // FIXME: A callback should disable checkers at the start of functions.
269 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
270 C.getCurrentAnalysisDeclContext()->getDecl())))
271 return;
272
273 ProgramStateRef state = C.getState();
274 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
275 if (!prevFlags)
276 return;
277 state = state->remove<PreCallSelfFlags>();
278
279 unsigned NumArgs = CE.getNumArgs();
280 for (unsigned i = 0; i < NumArgs; ++i) {
281 SVal argV = CE.getArgSVal(i);
282 if (isSelfVar(argV, C)) {
283 // If the address of 'self' is being passed to the call, assume that the
284 // 'self' after the call will have the same flags.
285 // EX: log(&self)
286 addSelfFlag(state, state->getSVal(argV.castAs<Loc>()), prevFlags, C);
287 return;
288 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
289 // If 'self' is passed to the call by value, assume that the function
290 // returns 'self'. So assign the flags, which were set on 'self' to the
291 // return value.
292 // EX: self = performMoreInitialization(self)
293 addSelfFlag(state, CE.getReturnValue(), prevFlags, C);
294 return;
295 }
296 }
297
298 C.addTransition(state);
299 }
300
301 void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad,
302 const Stmt *S,
303 CheckerContext &C) const {
304 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
305 C.getCurrentAnalysisDeclContext()->getDecl())))
306 return;
307
308 // Tag the result of a load from 'self' so that we can easily know that the
309 // value is the object that 'self' points to.
310 ProgramStateRef state = C.getState();
311 if (isSelfVar(location, C))
312 addSelfFlag(state, state->getSVal(location.castAs<Loc>()), SelfFlag_Self,
313 C);
314 }
315
316
317 void ObjCSelfInitChecker::checkBind(SVal loc, SVal val, const Stmt *S,
318 CheckerContext &C) const {
319 // Allow assignment of anything to self. Self is a local variable in the
320 // initializer, so it is legal to assign anything to it, like results of
321 // static functions/method calls. After self is assigned something we cannot
322 // reason about, stop enforcing the rules.
323 // (Only continue checking if the assigned value should be treated as self.)
324 if ((isSelfVar(loc, C)) &&
325 !hasSelfFlag(val, SelfFlag_InitRes, C) &&
326 !hasSelfFlag(val, SelfFlag_Self, C) &&
327 !isSelfVar(val, C)) {
328
329 // Stop tracking the checker-specific state in the state.
330 ProgramStateRef State = C.getState();
331 State = State->remove<CalledInit>();
332 if (SymbolRef sym = loc.getAsSymbol())
333 State = State->remove<SelfFlag>(sym);
334 C.addTransition(State);
335 }
336 }
337
338 void ObjCSelfInitChecker::printState(raw_ostream &Out, ProgramStateRef State,
339 const char *NL, const char *Sep) const {
340 SelfFlagTy FlagMap = State->get<SelfFlag>();
341 bool DidCallInit = State->get<CalledInit>();
342 SelfFlagEnum PreCallFlags = (SelfFlagEnum)State->get<PreCallSelfFlags>();
343
344 if (FlagMap.isEmpty() && !DidCallInit && !PreCallFlags)
345 return;
346
347 Out << Sep << NL << *this << " :" << NL;
348
349 if (DidCallInit)
350 Out << " An init method has been called." << NL;
351
352 if (PreCallFlags != SelfFlag_None) {
353 if (PreCallFlags & SelfFlag_Self) {
354 Out << " An argument of the current call came from the 'self' variable."
355 << NL;
356 }
357 if (PreCallFlags & SelfFlag_InitRes) {
358 Out << " An argument of the current call came from an init method."
359 << NL;
360 }
361 }
362
363 Out << NL;
364 for (SelfFlagTy::iterator I = FlagMap.begin(), E = FlagMap.end();
365 I != E; ++I) {
366 Out << I->first << " : ";
367
368 if (I->second == SelfFlag_None)
369 Out << "none";
370
371 if (I->second & SelfFlag_Self)
372 Out << "self variable";
373
374 if (I->second & SelfFlag_InitRes) {
375 if (I->second != SelfFlag_InitRes)
376 Out << " | ";
377 Out << "result of init method";
378 }
379
380 Out << NL;
381 }
382 }
383
384
385 // FIXME: A callback should disable checkers at the start of functions.
386 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) {
387 if (!ND)
388 return false;
389
390 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND);
391 if (!MD)
392 return false;
393 if (!isInitializationMethod(MD))
394 return false;
395
396 // self = [super init] applies only to NSObject subclasses.
397 // For instance, NSProxy doesn't implement -init.
398 ASTContext &Ctx = MD->getASTContext();
399 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
400 ObjCInterfaceDecl *ID = MD->getClassInterface()->getSuperClass();
401 for ( ; ID ; ID = ID->getSuperClass()) {
402 IdentifierInfo *II = ID->getIdentifier();
403
404 if (II == NSObjectII)
405 break;
406 }
407 return ID != nullptr;
408 }
409
410 /// Returns true if the location is 'self'.
411 static bool isSelfVar(SVal location, CheckerContext &C) {
412 AnalysisDeclContext *analCtx = C.getCurrentAnalysisDeclContext();
413 if (!analCtx->getSelfDecl())
414 return false;
415 if (!location.getAs<loc::MemRegionVal>())
416 return false;
417
418 loc::MemRegionVal MRV = location.castAs<loc::MemRegionVal>();
419 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts()))
420 return (DR->getDecl() == analCtx->getSelfDecl());
421
422 return false;
423 }
424
425 static bool isInitializationMethod(const ObjCMethodDecl *MD) {
426 return MD->getMethodFamily() == OMF_init;
427 }
428
429 static bool isInitMessage(const ObjCMethodCall &Call) {
430 return Call.getMethodFamily() == OMF_init;
431 }
432
433 //===----------------------------------------------------------------------===//
434 // Registration.
435 //===----------------------------------------------------------------------===//
436
437 void ento::registerObjCSelfInitChecker(CheckerManager &mgr) {
438 mgr.registerChecker<ObjCSelfInitChecker>();
439 }
clang::Builtin::ID
ID
Definition: Builtins.h:49
ento
clang::ento::categories::CoreFoundationObjectiveC
const char *const CoreFoundationObjectiveC
Definition: CommonBugCategories.cpp:15
SelfFlagEnum
SelfFlagEnum
Definition: ObjCSelfInitChecker.cpp:88
clang::ObjCMethodDecl::getClassInterface
ObjCInterfaceDecl * getClassInterface()
Definition: DeclObjC.cpp:1144
clang::ento::SymbolRef
const SymExpr * SymbolRef
Definition: PathDiagnostic.h:59
clang::Stmt
Stmt - This represents one statement.
Definition: Stmt.h:66
clang::ento::ProgramStateRef
IntrusiveRefCntPtr< const ProgramState > ProgramStateRef
Definition: ProgramState_Fwd.h:38
BugType.h
clang::ObjCMethodDecl
ObjCMethodDecl - Represents an instance or class method declaration.
Definition: DeclObjC.h:139
clang::NamedDecl::getIdentifier
IdentifierInfo * getIdentifier() const
Get the identifier that names this declaration, if there is one.
Definition: Decl.h:270
clang::IdentifierInfo
One of these records is kept for each identifier that is lexed.
Definition: IdentifierTable.h:58
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:134
clang::ASTContext
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:155
State
LineState State
Definition: UnwrappedLineFormatter.cpp:877
clang::AnalysisDeclContext
AnalysisDeclContext contains the context data for the function or method under analysis.
Definition: AnalysisDeclContext.h:70
Checker.h
CheckerManager.h
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:748
clang::ASTContext::Idents
IdentifierTable & Idents
Definition: ASTContext.h:566
isInitMessage
static bool isInitMessage(const ObjCMethodCall &Msg)
Definition: ObjCSelfInitChecker.cpp:429
isInitializationMethod
static bool isInitializationMethod(const ObjCMethodDecl *MD)
Definition: ObjCSelfInitChecker.cpp:425
clang::ObjCMethodDecl::getMethodFamily
ObjCMethodFamily getMethodFamily() const
Determines the family of this method.
Definition: DeclObjC.cpp:986
clang::ObjCMethodCall
Represents any expression that calls an Objective-C method.
Definition: CallEvent.h:970
addSelfFlag
static void addSelfFlag(ProgramStateRef state, SVal val, SelfFlagEnum flag, CheckerContext &C)
Definition: ObjCSelfInitChecker.cpp:118
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:107
clang::ObjCInterfaceDecl
Represents an ObjC class declaration.
Definition: DeclObjC.h:1172
clang::Expr
This represents one expression.
Definition: Expr.h:106
ParentMap.h
shouldRunOnFunctionOrMethod
static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND)
Definition: ObjCSelfInitChecker.cpp:386
clang::ObjCInterfaceDecl::getSuperClass
ObjCInterfaceDecl * getSuperClass() const
Definition: DeclObjC.cpp:338
clang::ReturnStmt
ReturnStmt - This represents a return, optionally of an expression: return; return 4;...
Definition: Stmt.h:2443
BuiltinCheckerRegistration.h
clang::AnalysisDeclContext::getSelfDecl
const ImplicitParamDecl * getSelfDecl() const
Return the ImplicitParamDecl* associated with &#39;self&#39; if this AnalysisDeclContext wraps an ObjCMethodD...
Definition: AnalysisDeclContext.cpp:147
hasSelfFlag
static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C)
Definition: ObjCSelfInitChecker.cpp:127
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:34
clang::IdentifierTable::get
IdentifierInfo & get(StringRef Name)
Return the identifier token info for the specified named identifier.
Definition: IdentifierTable.h:519
clang::ReturnStmt::getRetValue
Expr * getRetValue()
Definition: Stmt.h:2476
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:85
clang::Decl::getASTContext
ASTContext & getASTContext() const LLVM_READONLY
Definition: DeclBase.cpp:376
isSelfVar
static bool isSelfVar(SVal location, CheckerContext &C)
Returns true if the location is &#39;self&#39;.
Definition: ObjCSelfInitChecker.cpp:411
clang::ObjCMethodCall::getOriginExpr
virtual const ObjCMessageExpr * getOriginExpr() const
Definition: CallEvent.h:994
clang
Dataflow Directional Tag Classes.
Definition: CFGReachabilityAnalysis.h:22
clang::ObjCMethodCall::getMethodFamily
ObjCMethodFamily getMethodFamily() const
Definition: CallEvent.h:1014
clang::ObjCIvarRefExpr::getBase
const Expr * getBase() const
Definition: ExprObjC.h:547
clang::ObjCIvarRefExpr
ObjCIvarRefExpr - A reference to an ObjC instance variable.
Definition: ExprObjC.h:513
clang::OMF_init
Definition: IdentifierTable.h:621
clang::NamedDecl
This represents a decl that may have a name.
Definition: Decl.h:249
ProgramStateTrait.h
CallEvent.h
CallEvent
CheckerContext.h