ObjCSelfInitChecker.cpp revision 85f3d76c0ecfdefcf83ea44a57b7a16119c8a045
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 wih 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// FIXME (rdar://7937506): In the case of: 38// [super init]; 39// return self; 40// Have an extra PathDiagnosticPiece in the path that says "called [super init], 41// but didn't assign the result to self." 42 43//===----------------------------------------------------------------------===// 44 45// FIXME: Somehow stick the link to Apple's documentation about initializing 46// objects in the diagnostics. 47// http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Articles/ocAllocInit.html 48 49#include "ClangSACheckers.h" 50#include "clang/StaticAnalyzer/Core/Checker.h" 51#include "clang/StaticAnalyzer/Core/CheckerManager.h" 52#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h" 53#include "clang/StaticAnalyzer/Core/PathSensitive/GRStateTrait.h" 54#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h" 55#include "clang/AST/ParentMap.h" 56 57using namespace clang; 58using namespace ento; 59 60static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND); 61static bool isInitializationMethod(const ObjCMethodDecl *MD); 62static bool isInitMessage(const ObjCMessage &msg); 63static bool isSelfVar(SVal location, CheckerContext &C); 64 65namespace { 66class ObjCSelfInitChecker : public Checker< 67 check::PostObjCMessage, 68 check::PostStmt<ObjCIvarRefExpr>, 69 check::PreStmt<ReturnStmt>, 70 check::PreStmt<CallExpr>, 71 check::PostStmt<CallExpr>, 72 check::Location > { 73public: 74 void checkPostObjCMessage(ObjCMessage msg, CheckerContext &C) const; 75 void checkPostStmt(const ObjCIvarRefExpr *E, CheckerContext &C) const; 76 void checkPreStmt(const ReturnStmt *S, CheckerContext &C) const; 77 void checkPreStmt(const CallExpr *CE, CheckerContext &C) const; 78 void checkPostStmt(const CallExpr *CE, CheckerContext &C) const; 79 void checkLocation(SVal location, bool isLoad, CheckerContext &C) const; 80}; 81} // end anonymous namespace 82 83namespace { 84 85class InitSelfBug : public BugType { 86 const std::string desc; 87public: 88 InitSelfBug() : BugType("missing \"self = [(super or self) init...]\"", 89 "missing \"self = [(super or self) init...]\"") {} 90}; 91 92} // end anonymous namespace 93 94namespace { 95enum SelfFlagEnum { 96 /// \brief No flag set. 97 SelfFlag_None = 0x0, 98 /// \brief Value came from 'self'. 99 SelfFlag_Self = 0x1, 100 /// \brief Value came from the result of an initializer (e.g. [super init]). 101 SelfFlag_InitRes = 0x2 102}; 103} 104 105typedef llvm::ImmutableMap<SymbolRef, unsigned> SelfFlag; 106namespace { struct CalledInit {}; } 107namespace { struct PreCallSelfFlags {}; } 108 109namespace clang { 110namespace ento { 111 template<> 112 struct GRStateTrait<SelfFlag> : public GRStatePartialTrait<SelfFlag> { 113 static void* GDMIndex() { static int index = 0; return &index; } 114 }; 115 template <> 116 struct GRStateTrait<CalledInit> : public GRStatePartialTrait<bool> { 117 static void *GDMIndex() { static int index = 0; return &index; } 118 }; 119 120 /// \brief A call receiving a reference to 'self' invalidates the object that 121 /// 'self' contains. This keeps the "self flags" assigned to the 'self' 122 /// object before the call so we can assign them to the new object that 'self' 123 /// points to after the call. 124 template <> 125 struct GRStateTrait<PreCallSelfFlags> : public GRStatePartialTrait<unsigned> { 126 static void *GDMIndex() { static int index = 0; return &index; } 127 }; 128} 129} 130 131static SelfFlagEnum getSelfFlags(SVal val, const GRState *state) { 132 if (SymbolRef sym = val.getAsSymbol()) 133 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym)) 134 return (SelfFlagEnum)*attachedFlags; 135 return SelfFlag_None; 136} 137 138static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) { 139 return getSelfFlags(val, C.getState()); 140} 141 142static void addSelfFlag(const GRState *state, SVal val, 143 SelfFlagEnum flag, CheckerContext &C) { 144 // We tag the symbol that the SVal wraps. 145 if (SymbolRef sym = val.getAsSymbol()) 146 C.addTransition(state->set<SelfFlag>(sym, getSelfFlags(val, C) | flag)); 147} 148 149static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) { 150 return getSelfFlags(val, C) & flag; 151} 152 153/// \brief Returns true of the value of the expression is the object that 'self' 154/// points to and is an object that did not come from the result of calling 155/// an initializer. 156static bool isInvalidSelf(const Expr *E, CheckerContext &C) { 157 SVal exprVal = C.getState()->getSVal(E); 158 if (!hasSelfFlag(exprVal, SelfFlag_Self, C)) 159 return false; // value did not come from 'self'. 160 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C)) 161 return false; // 'self' is properly initialized. 162 163 return true; 164} 165 166static void checkForInvalidSelf(const Expr *E, CheckerContext &C, 167 const char *errorStr) { 168 if (!E) 169 return; 170 171 if (!C.getState()->get<CalledInit>()) 172 return; 173 174 if (!isInvalidSelf(E, C)) 175 return; 176 177 // Generate an error node. 178 ExplodedNode *N = C.generateSink(); 179 if (!N) 180 return; 181 182 EnhancedBugReport *report = 183 new EnhancedBugReport(*new InitSelfBug(), errorStr, N); 184 C.EmitReport(report); 185} 186 187void ObjCSelfInitChecker::checkPostObjCMessage(ObjCMessage msg, 188 CheckerContext &C) const { 189 // When encountering a message that does initialization (init rule), 190 // tag the return value so that we know later on that if self has this value 191 // then it is properly initialized. 192 193 // FIXME: A callback should disable checkers at the start of functions. 194 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( 195 C.getCurrentAnalysisContext()->getDecl()))) 196 return; 197 198 if (isInitMessage(msg)) { 199 // Tag the return value as the result of an initializer. 200 const GRState *state = C.getState(); 201 202 // FIXME this really should be context sensitive, where we record 203 // the current stack frame (for IPA). Also, we need to clean this 204 // value out when we return from this method. 205 state = state->set<CalledInit>(true); 206 207 SVal V = state->getSVal(msg.getOriginExpr()); 208 addSelfFlag(state, V, SelfFlag_InitRes, C); 209 return; 210 } 211 212 // 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 215 // fails. 216} 217 218void 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.getCurrentAnalysisContext()->getDecl()))) 223 return; 224 225 checkForInvalidSelf(E->getBase(), C, 226 "Instance variable used while 'self' is not set to the result of " 227 "'[(super or self) init...]'"); 228} 229 230void 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.getCurrentAnalysisContext()->getDecl()))) 235 return; 236 237 checkForInvalidSelf(S->getRetValue(), C, 238 "Returning 'self' while it is not set to the result of " 239 "'[(super or self) init...]'"); 240} 241 242// 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 245// functions. 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: 249// @code 250// if (!(self = [super init])) 251// return nil; 252// if (!(self = _commonInit(self))) 253// return nil; 254// @endcode 255// Until we can use inter-procedural analysis, in such a call, transfer the 256// SelfFlags to the result of the call. 257 258void ObjCSelfInitChecker::checkPreStmt(const CallExpr *CE, 259 CheckerContext &C) const { 260 const GRState *state = C.getState(); 261 for (CallExpr::const_arg_iterator 262 I = CE->arg_begin(), E = CE->arg_end(); I != E; ++I) { 263 SVal argV = state->getSVal(*I); 264 if (isSelfVar(argV, C)) { 265 unsigned selfFlags = getSelfFlags(state->getSVal(cast<Loc>(argV)), C); 266 C.addTransition(state->set<PreCallSelfFlags>(selfFlags)); 267 return; 268 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) { 269 unsigned selfFlags = getSelfFlags(argV, C); 270 C.addTransition(state->set<PreCallSelfFlags>(selfFlags)); 271 return; 272 } 273 } 274} 275 276void ObjCSelfInitChecker::checkPostStmt(const CallExpr *CE, 277 CheckerContext &C) const { 278 const GRState *state = C.getState(); 279 for (CallExpr::const_arg_iterator 280 I = CE->arg_begin(), E = CE->arg_end(); I != E; ++I) { 281 SVal argV = state->getSVal(*I); 282 if (isSelfVar(argV, C)) { 283 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>(); 284 state = state->remove<PreCallSelfFlags>(); 285 addSelfFlag(state, state->getSVal(cast<Loc>(argV)), prevFlags, C); 286 return; 287 } else if (hasSelfFlag(argV, SelfFlag_Self, C)) { 288 SelfFlagEnum prevFlags = (SelfFlagEnum)state->get<PreCallSelfFlags>(); 289 state = state->remove<PreCallSelfFlags>(); 290 addSelfFlag(state, state->getSVal(CE), prevFlags, C); 291 return; 292 } 293 } 294} 295 296void ObjCSelfInitChecker::checkLocation(SVal location, bool isLoad, 297 CheckerContext &C) const { 298 // Tag the result of a load from 'self' so that we can easily know that the 299 // value is the object that 'self' points to. 300 const GRState *state = C.getState(); 301 if (isSelfVar(location, C)) 302 addSelfFlag(state, state->getSVal(cast<Loc>(location)), SelfFlag_Self, C); 303} 304 305// FIXME: A callback should disable checkers at the start of functions. 306static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) { 307 if (!ND) 308 return false; 309 310 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND); 311 if (!MD) 312 return false; 313 if (!isInitializationMethod(MD)) 314 return false; 315 316 // self = [super init] applies only to NSObject subclasses. 317 // For instance, NSProxy doesn't implement -init. 318 ASTContext& Ctx = MD->getASTContext(); 319 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject"); 320 ObjCInterfaceDecl* ID = MD->getClassInterface()->getSuperClass(); 321 for ( ; ID ; ID = ID->getSuperClass()) { 322 IdentifierInfo *II = ID->getIdentifier(); 323 324 if (II == NSObjectII) 325 break; 326 } 327 if (!ID) 328 return false; 329 330 return true; 331} 332 333/// \brief Returns true if the location is 'self'. 334static bool isSelfVar(SVal location, CheckerContext &C) { 335 AnalysisContext *analCtx = C.getCurrentAnalysisContext(); 336 if (!analCtx->getSelfDecl()) 337 return false; 338 if (!isa<loc::MemRegionVal>(location)) 339 return false; 340 341 loc::MemRegionVal MRV = cast<loc::MemRegionVal>(location); 342 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.getRegion())) 343 return (DR->getDecl() == analCtx->getSelfDecl()); 344 345 return false; 346} 347 348static bool isInitializationMethod(const ObjCMethodDecl *MD) { 349 return MD->getMethodFamily() == OMF_init; 350} 351 352static bool isInitMessage(const ObjCMessage &msg) { 353 return msg.getMethodFamily() == OMF_init; 354} 355 356//===----------------------------------------------------------------------===// 357// Registration. 358//===----------------------------------------------------------------------===// 359 360void ento::registerObjCSelfInitChecker(CheckerManager &mgr) { 361 mgr.registerChecker<ObjCSelfInitChecker>(); 362} 363