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/CheckerContext.h"
43 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
44 #include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.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 ObjCMessage &msg);
54 static bool isSelfVar(SVal location, CheckerContext &C);
57 class ObjCSelfInitChecker : public Checker< check::PreObjCMessage,
58 check::PostObjCMessage,
59 check::PostStmt<ObjCIvarRefExpr>,
60 check::PreStmt<ReturnStmt>,
61 check::PreStmt<CallExpr>,
62 check::PostStmt<CallExpr>,
65 void checkPreObjCMessage(ObjCMessage msg, CheckerContext &C) const;
66 void checkPostObjCMessage(ObjCMessage msg, CheckerContext &C) const;
67 void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const;
68 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const;
69 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
70 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const;
71 void checkLocation(SVal location, bool isLoad, const Stmt *S,
72 CheckerContext &C) const;
74 void checkPreStmt(const CallOrObjCMessage &CE, CheckerContext &C) const;
75 void checkPostStmt(const CallOrObjCMessage &CE, CheckerContext &C) 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 typedef llvm::ImmutableMap<SymbolRef, unsigned> SelfFlag;
103 namespace { struct CalledInit {}; }
104 namespace { struct PreCallSelfFlags {}; }
109 struct ProgramStateTrait<SelfFlag> : public ProgramStatePartialTrait<SelfFlag> {
110 static void *GDMIndex() { static int index = 0; return &index; }
113 struct ProgramStateTrait<CalledInit> : public ProgramStatePartialTrait<bool> {
114 static void *GDMIndex() { static int index = 0; return &index; }
117 /// \brief A call receiving a reference to 'self' invalidates the object that
118 /// 'self' contains. This keeps the "self flags" assigned to the 'self'
119 /// object before the call so we can assign them to the new object that 'self'
120 /// points to after the call.
122 struct ProgramStateTrait<PreCallSelfFlags> : public ProgramStatePartialTrait<unsigned> {
123 static void *GDMIndex() { static int index = 0; return &index; }
128 static SelfFlagEnum getSelfFlags(SVal val, ProgramStateRef state) {
129 if (SymbolRef sym = val.getAsSymbol())
130 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym))
131 return (SelfFlagEnum)*attachedFlags;
132 return SelfFlag_None;
135 static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) {
136 return getSelfFlags(val, C.getState());
139 static void addSelfFlag(ProgramStateRef state, SVal val,
140 SelfFlagEnum flag, CheckerContext &C) {
141 // We tag the symbol that the SVal wraps.
142 if (SymbolRef sym = val.getAsSymbol())
143 C.addTransition(state->set<SelfFlag>(sym, getSelfFlags(val, C) | flag));
146 static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) {
147 return getSelfFlags(val, C) & flag;
150 /// \brief Returns true of the value of the expression is the object that 'self'
151 /// points to and is an object that did not come from the result of calling
153 static bool isInvalidSelf(const Expr *E, CheckerContext &C) {
154 SVal exprVal = C.getState()->getSVal(E, C.getLocationContext());
155 if (!hasSelfFlag(exprVal, SelfFlag_Self, C))
156 return false; // value did not come from 'self'.
157 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C))
158 return false; // 'self' is properly initialized.
163 static void checkForInvalidSelf(const Expr *E, CheckerContext &C,
164 const char *errorStr) {
168 if (!C.getState()->get<CalledInit>())
171 if (!isInvalidSelf(E, C))
174 // Generate an error node.
175 ExplodedNode *N = C.generateSink();
180 new BugReport(*new InitSelfBug(), errorStr, N);
181 C.EmitReport(report);
184 void ObjCSelfInitChecker::checkPostObjCMessage(ObjCMessage msg,
185 CheckerContext &C) const {
186 // When encountering a message that does initialization (init rule),
187 // tag the return value so that we know later on that if self has this value
188 // then it is properly initialized.
190 // FIXME: A callback should disable checkers at the start of functions.
191 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
192 C.getCurrentAnalysisDeclContext()->getDecl())))
195 if (isInitMessage(msg)) {
196 // Tag the return value as the result of an initializer.
197 ProgramStateRef state = C.getState();
199 // FIXME this really should be context sensitive, where we record
200 // the current stack frame (for IPA). Also, we need to clean this
201 // value out when we return from this method.
202 state = state->set<CalledInit>(true);
204 SVal V = state->getSVal(msg.getMessageExpr(), C.getLocationContext());
205 addSelfFlag(state, V, SelfFlag_InitRes, C);
209 CallOrObjCMessage MsgWrapper(msg, C.getState(), C.getLocationContext());
210 checkPostStmt(MsgWrapper, C);
212 // We don't check for an invalid 'self' in an obj-c message expression to cut
213 // down false positives where logging functions get information from self
214 // (like its class) or doing "invalidation" on self when the initialization
218 void ObjCSelfInitChecker::checkPostStmt(const ObjCIvarRefExpr *E,
219 CheckerContext &C) const {
220 // FIXME: A callback should disable checkers at the start of functions.
221 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
222 C.getCurrentAnalysisDeclContext()->getDecl())))
225 checkForInvalidSelf(E->getBase(), C,
226 "Instance variable used while 'self' is not set to the result of "
227 "'[(super or self) init...]'");
230 void ObjCSelfInitChecker::checkPreStmt(const ReturnStmt *S,
231 CheckerContext &C) const {
232 // FIXME: A callback should disable checkers at the start of functions.
233 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>(
234 C.getCurrentAnalysisDeclContext()->getDecl())))
237 checkForInvalidSelf(S->getRetValue(), C,
238 "Returning 'self' while it is not set to the result of "
239 "'[(super or self) init...]'");
242 // When a call receives a reference to 'self', [Pre/Post]VisitGenericCall pass
243 // the SelfFlags from the object 'self' point to before the call, to the new
244 // object after the call. This is to avoid invalidation of 'self' by logging
246 // Another common pattern in classes with multiple initializers is to put the
247 // subclass's common initialization bits into a static function that receives
248 // the value of 'self', e.g:
250 // if (!(self = [super init]))
252 // if (!(self = _commonInit(self)))
255 // Until we can use inter-procedural analysis, in such a call, transfer the
256 // SelfFlags to the result of the call.
258 void ObjCSelfInitChecker::checkPreStmt(const CallExpr *CE,
259 CheckerContext &C) const {
260 CallOrObjCMessage CEWrapper(CE, C.getState(), C.getLocationContext());
261 checkPreStmt(CEWrapper, C);
264 void ObjCSelfInitChecker::checkPostStmt(const CallExpr *CE,
265 CheckerContext &C) const {
266 CallOrObjCMessage CEWrapper(CE, C.getState(), C.getLocationContext());
267 checkPostStmt(CEWrapper, C);
270 void ObjCSelfInitChecker::checkPreObjCMessage(ObjCMessage Msg,
271 CheckerContext &C) const {
272 CallOrObjCMessage MsgWrapper(Msg, C.getState(), C.getLocationContext());
273 checkPreStmt(MsgWrapper, C);
276 void ObjCSelfInitChecker::checkPreStmt(const CallOrObjCMessage &CE,
277 CheckerContext &C) const {
278 ProgramStateRef state = C.getState();
279 unsigned NumArgs = CE.getNumArgs();
280 // If we passed 'self' as and argument to the call, record it in the state
281 // to be propagated after the call.
282 // Note, we could have just given up, but try to be more optimistic here and
283 // assume that the functions are going to continue initialization or will not
285 for (unsigned i = 0; i < NumArgs; ++i) {
286 SVal argV = CE.getArgSVal(i);
287 if (isSelfVar(argV, C)) {
288 unsigned selfFlags = getSelfFlags(state->getSVal(cast<Loc>(argV)), C);
289 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
291 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
292 unsigned selfFlags = getSelfFlags(argV, C);
293 C.addTransition(state->set<PreCallSelfFlags>(selfFlags));
299 void ObjCSelfInitChecker::checkPostStmt(const CallOrObjCMessage &CE,
300 CheckerContext &C) const {
301 ProgramStateRef state = C.getState();
302 unsigned NumArgs = CE.getNumArgs();
303 for (unsigned i = 0; i < NumArgs; ++i) {
304 SVal argV = CE.getArgSVal(i);
305 if (isSelfVar(argV, C)) {
306 // If the address of 'self' is being passed to the call, assume that the
307 // 'self' after the call will have the same flags.
309 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
310 state = state->remove<PreCallSelfFlags>();
311 addSelfFlag(state, state->getSVal(cast<Loc>(argV)), prevFlags, C);
313 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) {
314 // If 'self' is passed to the call by value, assume that the function
315 // returns 'self'. So assign the flags, which were set on 'self' to the
317 // EX: self = performMoreInitialization(self)
318 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>();
319 state = state->remove<PreCallSelfFlags>();
320 const Expr *CallExpr = CE.getOriginExpr();
322 addSelfFlag(state, state->getSVal(CallExpr, C.getLocationContext()),
329 void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad,
331 CheckerContext &C) const {
332 // Tag the result of a load from 'self' so that we can easily know that the
333 // value is the object that 'self' points to.
334 ProgramStateRef state = C.getState();
335 if (isSelfVar(location, C))
336 addSelfFlag(state, state->getSVal(cast<Loc>(location)), SelfFlag_Self, C);
339 // FIXME: A callback should disable checkers at the start of functions.
340 static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) {
344 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND);
347 if (!isInitializationMethod(MD))
350 // self = [super init] applies only to NSObject subclasses.
351 // For instance, NSProxy doesn't implement -init.
352 ASTContext &Ctx = MD->getASTContext();
353 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject");
354 ObjCInterfaceDecl *ID = MD->getClassInterface()->getSuperClass();
355 for ( ; ID ; ID = ID->getSuperClass()) {
356 IdentifierInfo *II = ID->getIdentifier();
358 if (II == NSObjectII)
367 /// \brief Returns true if the location is 'self'.
368 static bool isSelfVar(SVal location, CheckerContext &C) {
369 AnalysisDeclContext *analCtx = C.getCurrentAnalysisDeclContext();
370 if (!analCtx->getSelfDecl())
372 if (!isa<loc::MemRegionVal>(location))
375 loc::MemRegionVal MRV = cast<loc::MemRegionVal>(location);
376 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.stripCasts()))
377 return (DR->getDecl() == analCtx->getSelfDecl());
382 static bool isInitializationMethod(const ObjCMethodDecl *MD) {
383 return MD->getMethodFamily() == OMF_init;
386 static bool isInitMessage(const ObjCMessage &msg) {
387 return msg.getMethodFamily() == OMF_init;
390 //===----------------------------------------------------------------------===//
392 //===----------------------------------------------------------------------===//
394 void ento::registerObjCSelfInitChecker(CheckerManager &mgr) {
395 mgr.registerChecker<ObjCSelfInitChecker>();