ObjCSelfInitChecker.cpp revision eaf969bf4b657f0c4577f38a39f8c4ef1d9272fc
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 "ExprEngineInternalChecks.h" 50#include "clang/StaticAnalyzer/PathSensitive/CheckerVisitor.h" 51#include "clang/StaticAnalyzer/PathSensitive/GRStateTrait.h" 52#include "clang/StaticAnalyzer/BugReporter/BugType.h" 53#include "clang/Analysis/DomainSpecific/CocoaConventions.h" 54#include "clang/AST/ParentMap.h" 55 56using namespace clang; 57using namespace ento; 58 59static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND); 60static bool isInitializationMethod(const ObjCMethodDecl *MD); 61static bool isInitMessage(const ObjCMessage &msg); 62static bool isSelfVar(SVal location, CheckerContext &C); 63 64namespace { 65enum SelfFlagEnum { 66 /// \brief No flag set. 67 SelfFlag_None = 0x0, 68 /// \brief Value came from 'self'. 69 SelfFlag_Self = 0x1, 70 /// \brief Value came from the result of an initializer (e.g. [super init]). 71 SelfFlag_InitRes = 0x2 72}; 73} 74 75namespace { 76class ObjCSelfInitChecker : public CheckerVisitor<ObjCSelfInitChecker> { 77 /// \brief A call receiving a reference to 'self' invalidates the object that 78 /// 'self' contains. This field keeps the "self flags" assigned to the 'self' 79 /// object before the call and assign them to the new object that 'self' 80 /// points to after the call. 81 SelfFlagEnum preCallSelfFlags; 82 83public: 84 static void *getTag() { static int tag = 0; return &tag; } 85 void postVisitObjCMessage(CheckerContext &C, ObjCMessage msg); 86 void PostVisitObjCIvarRefExpr(CheckerContext &C, const ObjCIvarRefExpr *E); 87 void PreVisitReturnStmt(CheckerContext &C, const ReturnStmt *S); 88 void PreVisitGenericCall(CheckerContext &C, const CallExpr *CE); 89 void PostVisitGenericCall(CheckerContext &C, const CallExpr *CE); 90 virtual void visitLocation(CheckerContext &C, const Stmt *S, SVal location, 91 bool isLoad); 92}; 93} // end anonymous namespace 94 95void ento::registerObjCSelfInitChecker(ExprEngine &Eng) { 96 if (Eng.getContext().getLangOptions().ObjC1) 97 Eng.registerCheck(new ObjCSelfInitChecker()); 98} 99 100namespace { 101 102class InitSelfBug : public BugType { 103 const std::string desc; 104public: 105 InitSelfBug() : BugType("missing \"self = [{initializer}]\"", 106 "missing \"self = [{initializer}]\"") {} 107}; 108 109} // end anonymous namespace 110 111typedef llvm::ImmutableMap<SymbolRef, unsigned> SelfFlag; 112 113namespace clang { 114namespace ento { 115 template<> 116 struct GRStateTrait<SelfFlag> : public GRStatePartialTrait<SelfFlag> { 117 static void* GDMIndex() { 118 static int index = 0; 119 return &index; 120 } 121 }; 122} 123} 124 125static SelfFlagEnum getSelfFlags(SVal val, const GRState *state) { 126 if (SymbolRef sym = val.getAsSymbol()) 127 if (const unsigned *attachedFlags = state->get<SelfFlag>(sym)) 128 return (SelfFlagEnum)*attachedFlags; 129 return SelfFlag_None; 130} 131 132static SelfFlagEnum getSelfFlags(SVal val, CheckerContext &C) { 133 return getSelfFlags(val, C.getState()); 134} 135 136static void addSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) { 137 const GRState *state = C.getState(); 138 // FIXME: We tag the symbol that the SVal wraps but this is conceptually 139 // wrong, we should tag the SVal; the fact that there is a symbol behind the 140 // SVal is irrelevant. 141 if (SymbolRef sym = val.getAsSymbol()) 142 C.addTransition(state->set<SelfFlag>(sym, getSelfFlags(val, C) | flag)); 143} 144 145static bool hasSelfFlag(SVal val, SelfFlagEnum flag, CheckerContext &C) { 146 return getSelfFlags(val, C) & flag; 147} 148 149/// \brief Returns true of the value of the expression is the object that 'self' 150/// points to and is an object that did not come from the result of calling 151/// an initializer. 152static bool isInvalidSelf(const Expr *E, CheckerContext &C) { 153 SVal exprVal = C.getState()->getSVal(E); 154 if (!hasSelfFlag(exprVal, SelfFlag_Self, C)) 155 return false; // value did not come from 'self'. 156 if (hasSelfFlag(exprVal, SelfFlag_InitRes, C)) 157 return false; // 'self' is properly initialized. 158 159 return true; 160} 161 162static void checkForInvalidSelf(const Expr *E, CheckerContext &C, 163 const char *errorStr) { 164 if (!E) 165 return; 166 if (!isInvalidSelf(E, C)) 167 return; 168 169 // Generate an error node. 170 ExplodedNode *N = C.generateSink(); 171 if (!N) 172 return; 173 174 EnhancedBugReport *report = 175 new EnhancedBugReport(*new InitSelfBug(), errorStr, N); 176 C.EmitReport(report); 177} 178 179void ObjCSelfInitChecker::postVisitObjCMessage(CheckerContext &C, 180 ObjCMessage msg) { 181 // When encountering a message that does initialization (init rule), 182 // tag the return value so that we know later on that if self has this value 183 // then it is properly initialized. 184 185 // FIXME: A callback should disable checkers at the start of functions. 186 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( 187 C.getCurrentAnalysisContext()->getDecl()))) 188 return; 189 190 if (isInitMessage(msg)) { 191 // Tag the return value as the result of an initializer. 192 const GRState *state = C.getState(); 193 SVal V = state->getSVal(msg.getOriginExpr()); 194 addSelfFlag(V, SelfFlag_InitRes, C); 195 return; 196 } 197 198 // We don't check for an invalid 'self' in an obj-c message expression to cut 199 // down false positives where logging functions get information from self 200 // (like its class) or doing "invalidation" on self when the initialization 201 // fails. 202} 203 204void ObjCSelfInitChecker::PostVisitObjCIvarRefExpr(CheckerContext &C, 205 const ObjCIvarRefExpr *E) { 206 // FIXME: A callback should disable checkers at the start of functions. 207 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( 208 C.getCurrentAnalysisContext()->getDecl()))) 209 return; 210 211 checkForInvalidSelf(E->getBase(), C, 212 "Using an ivar before setting 'self' to the result of an initializer"); 213} 214 215void ObjCSelfInitChecker::PreVisitReturnStmt(CheckerContext &C, 216 const ReturnStmt *S) { 217 // FIXME: A callback should disable checkers at the start of functions. 218 if (!shouldRunOnFunctionOrMethod(dyn_cast<NamedDecl>( 219 C.getCurrentAnalysisContext()->getDecl()))) 220 return; 221 222 checkForInvalidSelf(S->getRetValue(), C, 223 "Returning 'self' before setting it to the result of an initializer"); 224} 225 226// When a call receives a reference to 'self', [Pre/Post]VisitGenericCall pass 227// the SelfFlags from the object 'self' point to before the call, to the new 228// object after the call. 229 230void ObjCSelfInitChecker::PreVisitGenericCall(CheckerContext &C, 231 const CallExpr *CE) { 232 const GRState *state = C.getState(); 233 for (CallExpr::const_arg_iterator 234 I = CE->arg_begin(), E = CE->arg_end(); I != E; ++I) { 235 SVal argV = state->getSVal(*I); 236 if (isSelfVar(argV, C)) { 237 preCallSelfFlags = getSelfFlags(state->getSVal(cast<Loc>(argV)), C); 238 return; 239 } 240 } 241} 242 243void ObjCSelfInitChecker::PostVisitGenericCall(CheckerContext &C, 244 const CallExpr *CE) { 245 const GRState *state = C.getState(); 246 for (CallExpr::const_arg_iterator 247 I = CE->arg_begin(), E = CE->arg_end(); I != E; ++I) { 248 SVal argV = state->getSVal(*I); 249 if (isSelfVar(argV, C)) { 250 addSelfFlag(state->getSVal(cast<Loc>(argV)), preCallSelfFlags, C); 251 return; 252 } 253 } 254} 255 256void ObjCSelfInitChecker::visitLocation(CheckerContext &C, const Stmt *S, 257 SVal location, bool isLoad) { 258 // Tag the result of a load from 'self' so that we can easily know that the 259 // value is the object that 'self' points to. 260 const GRState *state = C.getState(); 261 if (isSelfVar(location, C)) 262 addSelfFlag(state->getSVal(cast<Loc>(location)), SelfFlag_Self, C); 263} 264 265// FIXME: A callback should disable checkers at the start of functions. 266static bool shouldRunOnFunctionOrMethod(const NamedDecl *ND) { 267 if (!ND) 268 return false; 269 270 const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(ND); 271 if (!MD) 272 return false; 273 if (!isInitializationMethod(MD)) 274 return false; 275 276 // self = [super init] applies only to NSObject subclasses. 277 // For instance, NSProxy doesn't implement -init. 278 ASTContext& Ctx = MD->getASTContext(); 279 IdentifierInfo* NSObjectII = &Ctx.Idents.get("NSObject"); 280 ObjCInterfaceDecl* ID = MD->getClassInterface()->getSuperClass(); 281 for ( ; ID ; ID = ID->getSuperClass()) { 282 IdentifierInfo *II = ID->getIdentifier(); 283 284 if (II == NSObjectII) 285 break; 286 } 287 if (!ID) 288 return false; 289 290 return true; 291} 292 293/// \brief Returns true if the location is 'self'. 294static bool isSelfVar(SVal location, CheckerContext &C) { 295 AnalysisContext *analCtx = C.getCurrentAnalysisContext(); 296 if (!analCtx->getSelfDecl()) 297 return false; 298 if (!isa<loc::MemRegionVal>(location)) 299 return false; 300 301 loc::MemRegionVal MRV = cast<loc::MemRegionVal>(location); 302 if (const DeclRegion *DR = dyn_cast<DeclRegion>(MRV.getRegion())) 303 return (DR->getDecl() == analCtx->getSelfDecl()); 304 305 return false; 306} 307 308static bool isInitializationMethod(const ObjCMethodDecl *MD) { 309 // Init methods with prefix like '-(id)_init' are private and the requirements 310 // are less strict so we don't check those. 311 return MD->isInstanceMethod() && 312 cocoa::deriveNamingConvention(MD->getSelector(), 313 /*ignorePrefix=*/false) == cocoa::InitRule; 314} 315 316static bool isInitMessage(const ObjCMessage &msg) { 317 return cocoa::deriveNamingConvention(msg.getSelector()) == cocoa::InitRule; 318} 319