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 "ClangSACheckers.h"
40 #include "clang/StaticAnalyzer/Core/Checker.h"
41 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
42 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
43 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
44 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
45 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
46 #include "clang/AST/ParentMap.h"
48 using namespace clang;
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);
57 class ObjCSelfInitChecker : public Checker< check::PostObjCMessage,
58 check::PostStmt<ObjCIvarRefExpr>,
59 check::PreStmt<ReturnStmt>,
65 void checkPostObjCMessage(const ObjCMethodCall &Msg, CheckerContext &C) const;
66 void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const;
67 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
68 void checkLocation(SVal location, bool isLoad, const Stmt *S,
69 CheckerContext &C) const;
70 void checkBind(SVal loc, SVal val, const Stmt *S, CheckerContext &C) const;
72 void checkPreCall(const CallEvent &CE, CheckerContext &C) const;
73 void checkPostCall(const CallEvent &CE, CheckerContext &C) const;
75 void printState(raw_ostream &Out, ProgramStateRef State,
76 const char *NL, const char *Sep) const;
78 } // end anonymous namespace
82 class InitSelfBug : public BugType {
83 const std::string desc;
85 InitSelfBug() : BugType("Missing \"self = [(super or self) init...]\"",
86 categories::CoreFoundationObjectiveC) {}
89 } // end anonymous namespace
93 /// \brief No flag set.
95 /// \brief Value came from 'self'.
97 /// \brief Value came from the result of an initializer (e.g. [super init]).
98 SelfFlag_InitRes = 0x2
102 REGISTER_MAP_WITH_PROGRAMSTATE(SelfFlag, SymbolRef, unsigned)
103 REGISTER_TRAIT_WITH_PROGRAMSTATE(CalledInit, bool)
105 /// \brief A call receiving a reference to 'self' invalidates the object that
106 /// 'self' contains. This keeps the "self flags" assigned to the 'self'
107 /// object before the call so we can assign them to the new object that 'self'
108 /// points to after the call.
109 REGISTER_TRAIT_WITH_PROGRAMSTATE(PreCallSelfFlags, unsigned)
111 static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state) {
112 if (SymbolRef sym = val.getAsSymbol())
113 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym))
114 return (SelfFlagEnum)*attachedFlags;
115 return SelfFlag_None;
118 static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) {
119 return getSelfFlags(val, C.getState());
122 static void addSelfFlag(ProgramStateRef state, SVal val,
123 SelfFlagEnum flag, CheckerContext &C) {
124 // We tag the symbol that the SVal wraps.
125 if (SymbolRef sym = val.getAsSymbol())
126 state = state->set<SelfFlag>(sym, getSelfFlags(val, state) | flag);
127 C.addTransition(state);
130 static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) {
131 return getSelfFlags(val, C) & flag;
134 /// \brief Returns true of the value of the expression is the object that 'self'
135 /// points to and is an object that did not come from the result of calling
137 static bool isInvalidSelf(const Expr *E, CheckerContext &C) {
138 SVal exprVal = C.getState()->getSVal(E, C.getLocationContext());
139 if (!hasSelfFlag(exprVal, SelfFlag_Self, C))
140 return false; // value did not come from 'self'.
141 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C))
142 return false; // 'self' is properly initialized.
147 static void checkForInvalidSelf(const Expr *E, CheckerContext &C,
148 const char *errorStr) {
152 if (!C.getState()->get<CalledInit>())
155 if (!isInvalidSelf(E, C))
158 // Generate an error node.
159 ExplodedNode *N = C.generateSink();
164 new BugReport(*new InitSelfBug(), errorStr, N);
165 C.emitReport(report);
168 void ObjCSelfInitChecker::checkPostObjCMessage(const ObjCMethodCall &Msg,
169 CheckerContext &C) const {
170 // When encountering a message that does initialization (init rule),
171 // tag the return value so that we know later on that if self has this value
172 // then it is properly initialized.
174 // FIXME: A callback should disable checkers at the start of functions.
175 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
176 C.getCurrentAnalysisDeclContext()->getDecl())))
179 if (isInitMessage(Msg)) {
180 // Tag the return value as the result of an initializer.
181 ProgramStateRef state = C.getState();
183 // FIXME this really should be context sensitive, where we record
184 // the current stack frame (for IPA). Also, we need to clean this
185 // value out when we return from this method.
186 state = state->set<CalledInit>(true);
188 SVal V = state->getSVal(Msg.getOriginExpr(), C.getLocationContext());
189 addSelfFlag(state, V, SelfFlag_InitRes, C);
193 // We don't check for an invalid 'self' in an obj-c message expression to cut
194 // down false positives where logging functions get information from self
195 // (like its class) or doing "invalidation" on self when the initialization
199 void ObjCSelfInitChecker::checkPostStmt(const ObjCIvarRefExpr *E,
200 CheckerContext &C) const {
201 // FIXME: A callback should disable checkers at the start of functions.
202 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
203 C.getCurrentAnalysisDeclContext()->getDecl())))
206 checkForInvalidSelf(E->getBase(), C,
207 "Instance variable used while 'self' is not set to the result of "
208 "'[(super or self) init...]'");
211 void ObjCSelfInitChecker::checkPreStmt(const ReturnStmt *S,
212 CheckerContext &C) const {
213 // FIXME: A callback should disable checkers at the start of functions.
214 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
215 C.getCurrentAnalysisDeclContext()->getDecl())))
218 checkForInvalidSelf(S->getRetValue(), C,
219 "Returning 'self' while it is not set to the result of "
220 "'[(super or self) init...]'");
223 // When a call receives a reference to 'self', [Pre/Post]Call pass
224 // the SelfFlags from the object 'self' points to before the call to the new
225 // object after the call. This is to avoid invalidation of 'self' by logging
227 // Another common pattern in classes with multiple initializers is to put the
228 // subclass's common initialization bits into a static function that receives
229 // the value of 'self', e.g:
231 // if (!(self = [super init]))
233 // if (!(self = _commonInit(self)))
236 // Until we can use inter-procedural analysis, in such a call, transfer the
237 // SelfFlags to the result of the call.
239 void ObjCSelfInitChecker::checkPreCall(const CallEvent &CE,
240 CheckerContext &C) const {
241 // FIXME: A callback should disable checkers at the start of functions.
242 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
243 C.getCurrentAnalysisDeclContext()->getDecl())))
246 ProgramStateRef state = C.getState();
247 unsigned NumArgs = CE.getNumArgs();
248 // If we passed 'self' as and argument to the call, record it in the state
249 // to be propagated after the call.
250 // Note, we could have just given up, but try to be more optimistic here and
251 // assume that the functions are going to continue initialization or will not
253 for (unsigned i = 0; i < NumArgs; ++i) {
254 SVal argV = CE.getArgSVal(i);
255 if (isSelfVar(argV, C)) {
256 unsigned selfFlags = getSelfFlags(state->getSVal(cast<Loc>(argV)), C);
257 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
259 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
260 unsigned selfFlags = getSelfFlags(argV, C);
261 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
267 void ObjCSelfInitChecker::checkPostCall(const CallEvent &CE,
268 CheckerContext &C) const {
269 // FIXME: A callback should disable checkers at the start of functions.
270 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
271 C.getCurrentAnalysisDeclContext()->getDecl())))
274 ProgramStateRef state = C.getState();
275 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
278 state = state->remove<PreCallSelfFlags>();
280 unsigned NumArgs = CE.getNumArgs();
281 for (unsigned i = 0; i < NumArgs; ++i) {
282 SVal argV = CE.getArgSVal(i);
283 if (isSelfVar(argV, C)) {
284 // If the address of 'self' is being passed to the call, assume that the
285 // 'self' after the call will have the same flags.
287 addSelfFlag(state, state->getSVal(cast<Loc>(argV)), prevFlags, C);
289 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
290 // If 'self' is passed to the call by value, assume that the function
291 // returns 'self'. So assign the flags, which were set on 'self' to the
293 // EX: self = performMoreInitialization(self)
294 addSelfFlag(state, CE.getReturnValue(), prevFlags, C);
299 C.addTransition(state);
302 void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad,
304 CheckerContext &C) const {
305 // Tag the result of a load from 'self' so that we can easily know that the
306 // value is the object that 'self' points to.
307 ProgramStateRef state = C.getState();
308 if (isSelfVar(location, C))
309 addSelfFlag(state, state->getSVal(cast<Loc>(location)), SelfFlag_Self, C);
313 void ObjCSelfInitChecker::checkBind(SVal loc, SVal val, const Stmt *S,
314 CheckerContext &C) const {
315 // Allow assignment of anything to self. Self is a local variable in the
316 // initializer, so it is legal to assign anything to it, like results of
317 // static functions/method calls. After self is assigned something we cannot
318 // reason about, stop enforcing the rules.
319 // (Only continue checking if the assigned value should be treated as self.)
320 if ((isSelfVar(loc, C)) &&
321 !hasSelfFlag(val, SelfFlag_InitRes, C) &&
322 !hasSelfFlag(val, SelfFlag_Self, C) &&
323 !isSelfVar(val, C)) {
325 // Stop tracking the checker-specific state in the state.
326 ProgramStateRef State = C.getState();
327 State = State->remove<CalledInit>();
328 if (SymbolRef sym = loc.getAsSymbol())
329 State = State->remove<SelfFlag>(sym);
330 C.addTransition(State);
334 void ObjCSelfInitChecker::printState(raw_ostream &Out, ProgramStateRef State,
335 const char *NL, const char *Sep) const {
336 SelfFlagTy FlagMap = State->get<SelfFlag>();
337 bool DidCallInit = State->get<CalledInit>();
338 SelfFlagEnum PreCallFlags = (SelfFlagEnum)State->get<PreCallSelfFlags>();
340 if (FlagMap.isEmpty() && !DidCallInit && !PreCallFlags)
343 Out << Sep << NL << "ObjCSelfInitChecker:" << NL;
346 Out << " An init method has been called." << NL;
348 if (PreCallFlags != SelfFlag_None) {
349 if (PreCallFlags & SelfFlag_Self) {
350 Out << " An argument of the current call came from the 'self' variable."
353 if (PreCallFlags & SelfFlag_InitRes) {
354 Out << " An argument of the current call came from an init method."
360 for (SelfFlagTy::iterator I = FlagMap.begin(), E = FlagMap.end();
362 Out << I->first << " : ";
364 if (I->second == SelfFlag_None)
367 if (I->second & SelfFlag_Self)
368 Out << "self variable";
370 if (I->second & SelfFlag_InitRes) {
371 if (I->second != SelfFlag_InitRes)
373 Out << "result of init method";
381 // FIXME: A callback should disable checkers at the start of functions.
382 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) {
386 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND);
389 if (!isInitializationMethod(MD))
392 // self = [super init] applies only to NSObject subclasses.
393 // For instance, NSProxy doesn't implement -init.
394 ASTContext &Ctx = MD->getASTContext();
395 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
396 ObjCInterfaceDecl *ID = MD->getClassInterface()->getSuperClass();
397 for ( ; ID ; ID = ID->getSuperClass()) {
398 IdentifierInfo *II = ID->getIdentifier();
400 if (II == NSObjectII)
409 /// \brief Returns true if the location is 'self'.
410 static bool isSelfVar(SVal location, CheckerContext &C) {
411 AnalysisDeclContext *analCtx = C.getCurrentAnalysisDeclContext();
412 if (!analCtx->getSelfDecl())
414 if (!isa<loc::MemRegionVal>(location))
417 loc::MemRegionVal MRV = cast<loc::MemRegionVal>(location);
418 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts()))
419 return (DR->getDecl() == analCtx->getSelfDecl());
424 static bool isInitializationMethod(const ObjCMethodDecl *MD) {
425 return MD->getMethodFamily() == OMF_init;
428 static bool isInitMessage(const ObjCMethodCall &Call) {
429 return Call.getMethodFamily() == OMF_init;
432 //===----------------------------------------------------------------------===//
434 //===----------------------------------------------------------------------===//
436 void ento::registerObjCSelfInitChecker(CheckerManager &mgr) {
437 mgr.registerChecker<ObjCSelfInitChecker>();