1 //== ObjCSelfInitChecker.cpp - Checker for 'self' initialization -*- C++ -*--=//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines ObjCSelfInitChecker, a builtin check that checks for uses of
11 // 'self' before proper initialization.
13 //===----------------------------------------------------------------------===//
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.
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]).
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.
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.
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.
37 //===----------------------------------------------------------------------===//
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"
49 using namespace clang;
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);
58 class ObjCSelfInitChecker : public Checker< check::PostObjCMessage,
59 check::PostStmt<ObjCIvarRefExpr>,
60 check::PreStmt<ReturnStmt>,
65 mutable std::unique_ptr<BugType> BT;
67 void checkForInvalidSelf(const Expr *E, CheckerContext &C,
68 const char *errorStr) const;
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;
79 void checkPreCall(const CallEvent &CE, CheckerContext &C) const;
80 void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
82 void printState(raw_ostream &Out, ProgramStateRef State,
83 const char *NL, const char *Sep) const override;
85 } // end anonymous namespace
91 /// Value came from 'self'.
93 /// Value came from the result of an initializer (e.g. [super init]).
94 SelfFlag_InitRes = 0x2
98 REGISTER_MAP_WITH_PROGRAMSTATE(SelfFlag, SymbolRef, unsigned)
99 REGISTER_TRAIT_WITH_PROGRAMSTATE(CalledInit, bool)
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)
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;
114 static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) {
115 return getSelfFlags(val, C.getState());
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);
127 static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) {
128 return getSelfFlags(val, C) & flag;
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
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.
144 void ObjCSelfInitChecker::checkForInvalidSelf(const Expr *E, CheckerContext &C,
145 const char *errorStr) const {
149 if (!C.getState()->get<CalledInit>())
152 if (!isInvalidSelf(E, C))
155 // Generate an error node.
156 ExplodedNode *N = C.generateErrorNode();
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));
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.
172 // FIXME: A callback should disable checkers at the start of functions.
173 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
174 C.getCurrentAnalysisDeclContext()->getDecl())))
177 if (isInitMessage(Msg)) {
178 // Tag the return value as the result of an initializer.
179 ProgramStateRef state = C.getState();
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);
186 SVal V = C.getSVal(Msg.getOriginExpr());
187 addSelfFlag(state, V, SelfFlag_InitRes, C);
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
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())))
206 "Instance variable used while 'self' is not set to the result of "
207 "'[(super or self) init...]'");
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())))
217 checkForInvalidSelf(S->getRetValue(), C,
218 "Returning 'self' while it is not set to the result of "
219 "'[(super or self) init...]'");
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
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:
230 // if (!(self = [super init]))
232 // if (!(self = _commonInit(self)))
235 // Until we can use inter-procedural analysis, in such a call, transfer the
236 // SelfFlags to the result of the call.
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())))
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
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));
258 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
259 unsigned selfFlags = getSelfFlags(argV, C);
260 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
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())))
273 ProgramStateRef state = C.getState();
274 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
277 state = state->remove<PreCallSelfFlags>();
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.
286 addSelfFlag(state, state->getSVal(argV.castAs<Loc>()), prevFlags, C);
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
292 // EX: self = performMoreInitialization(self)
293 addSelfFlag(state, CE.getReturnValue(), prevFlags, C);
298 C.addTransition(state);
301 void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad,
303 CheckerContext &C) const {
304 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
305 C.getCurrentAnalysisDeclContext()->getDecl())))
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,
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)) {
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);
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>();
344 if (FlagMap.isEmpty() && !DidCallInit && !PreCallFlags)
347 Out << Sep << NL << *this << " :" << NL;
350 Out << " An init method has been called." << NL;
352 if (PreCallFlags != SelfFlag_None) {
353 if (PreCallFlags & SelfFlag_Self) {
354 Out << " An argument of the current call came from the 'self' variable."
357 if (PreCallFlags & SelfFlag_InitRes) {
358 Out << " An argument of the current call came from an init method."
364 for (SelfFlagTy::iterator I = FlagMap.begin(), E = FlagMap.end();
366 Out << I->first << " : ";
368 if (I->second == SelfFlag_None)
371 if (I->second & SelfFlag_Self)
372 Out << "self variable";
374 if (I->second & SelfFlag_InitRes) {
375 if (I->second != SelfFlag_InitRes)
377 Out << "result of init method";
385 // FIXME: A callback should disable checkers at the start of functions.
386 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) {
390 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND);
393 if (!isInitializationMethod(MD))
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();
404 if (II == NSObjectII)
407 return ID != nullptr;
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())
415 if (!location.getAs<loc::MemRegionVal>())
418 loc::MemRegionVal MRV = location.castAs<loc::MemRegionVal>();
419 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts()))
420 return (DR->getDecl() == analCtx->getSelfDecl());
425 static bool isInitializationMethod(const ObjCMethodDecl *MD) {
426 return MD->getMethodFamily() == OMF_init;
429 static bool isInitMessage(const ObjCMethodCall &Call) {
430 return Call.getMethodFamily() == OMF_init;
433 //===----------------------------------------------------------------------===//
435 //===----------------------------------------------------------------------===//
437 void ento::registerObjCSelfInitChecker(CheckerManager &mgr) {
438 mgr.registerChecker<ObjCSelfInitChecker>();