ExprEngineObjC.cpp revision 226633
1//=-- ExprEngineObjC.cpp - ExprEngine support for Objective-C ---*- 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 file defines ExprEngine's support for Objective-C expressions. 11// 12//===----------------------------------------------------------------------===// 13 14#include "clang/StaticAnalyzer/Core/CheckerManager.h" 15#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h" 17#include "clang/Analysis/Support/SaveAndRestore.h" 18 19using namespace clang; 20using namespace ento; 21 22void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex, 23 ExplodedNode *Pred, 24 ExplodedNodeSet &Dst) { 25 26 const ProgramState *state = Pred->getState(); 27 SVal baseVal = state->getSVal(Ex->getBase()); 28 SVal location = state->getLValue(Ex->getDecl(), baseVal); 29 30 ExplodedNodeSet dstIvar; 31 MakeNode(dstIvar, Ex, Pred, state->BindExpr(Ex, location)); 32 33 // Perform the post-condition check of the ObjCIvarRefExpr and store 34 // the created nodes in 'Dst'. 35 getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this); 36} 37 38void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S, 39 ExplodedNode *Pred, 40 ExplodedNodeSet &Dst) { 41 getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this); 42} 43 44void ExprEngine::VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S, 45 ExplodedNode *Pred, 46 ExplodedNodeSet &Dst) { 47 48 // ObjCForCollectionStmts are processed in two places. This method 49 // handles the case where an ObjCForCollectionStmt* occurs as one of the 50 // statements within a basic block. This transfer function does two things: 51 // 52 // (1) binds the next container value to 'element'. This creates a new 53 // node in the ExplodedGraph. 54 // 55 // (2) binds the value 0/1 to the ObjCForCollectionStmt* itself, indicating 56 // whether or not the container has any more elements. This value 57 // will be tested in ProcessBranch. We need to explicitly bind 58 // this value because a container can contain nil elements. 59 // 60 // FIXME: Eventually this logic should actually do dispatches to 61 // 'countByEnumeratingWithState:objects:count:' (NSFastEnumeration). 62 // This will require simulating a temporary NSFastEnumerationState, either 63 // through an SVal or through the use of MemRegions. This value can 64 // be affixed to the ObjCForCollectionStmt* instead of 0/1; when the loop 65 // terminates we reclaim the temporary (it goes out of scope) and we 66 // we can test if the SVal is 0 or if the MemRegion is null (depending 67 // on what approach we take). 68 // 69 // For now: simulate (1) by assigning either a symbol or nil if the 70 // container is empty. Thus this transfer function will by default 71 // result in state splitting. 72 73 const Stmt *elem = S->getElement(); 74 const ProgramState *state = Pred->getState(); 75 SVal elementV; 76 77 if (const DeclStmt *DS = dyn_cast<DeclStmt>(elem)) { 78 const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl()); 79 assert(elemD->getInit() == 0); 80 elementV = state->getLValue(elemD, Pred->getLocationContext()); 81 } 82 else { 83 elementV = state->getSVal(elem); 84 } 85 86 ExplodedNodeSet dstLocation; 87 evalLocation(dstLocation, elem, Pred, state, elementV, NULL, false); 88 89 if (dstLocation.empty()) 90 return; 91 92 for (ExplodedNodeSet::iterator NI = dstLocation.begin(), 93 NE = dstLocation.end(); NI!=NE; ++NI) { 94 Pred = *NI; 95 const ProgramState *state = Pred->getState(); 96 97 // Handle the case where the container still has elements. 98 SVal TrueV = svalBuilder.makeTruthVal(1); 99 const ProgramState *hasElems = state->BindExpr(S, TrueV); 100 101 // Handle the case where the container has no elements. 102 SVal FalseV = svalBuilder.makeTruthVal(0); 103 const ProgramState *noElems = state->BindExpr(S, FalseV); 104 105 if (loc::MemRegionVal *MV = dyn_cast<loc::MemRegionVal>(&elementV)) 106 if (const TypedValueRegion *R = 107 dyn_cast<TypedValueRegion>(MV->getRegion())) { 108 // FIXME: The proper thing to do is to really iterate over the 109 // container. We will do this with dispatch logic to the store. 110 // For now, just 'conjure' up a symbolic value. 111 QualType T = R->getValueType(); 112 assert(Loc::isLocType(T)); 113 unsigned Count = Builder->getCurrentBlockCount(); 114 SymbolRef Sym = SymMgr.getConjuredSymbol(elem, T, Count); 115 SVal V = svalBuilder.makeLoc(Sym); 116 hasElems = hasElems->bindLoc(elementV, V); 117 118 // Bind the location to 'nil' on the false branch. 119 SVal nilV = svalBuilder.makeIntVal(0, T); 120 noElems = noElems->bindLoc(elementV, nilV); 121 } 122 123 // Create the new nodes. 124 MakeNode(Dst, S, Pred, hasElems); 125 MakeNode(Dst, S, Pred, noElems); 126 } 127} 128 129void ExprEngine::VisitObjCMessage(const ObjCMessage &msg, 130 ExplodedNode *Pred, 131 ExplodedNodeSet &Dst) { 132 133 // Handle the previsits checks. 134 ExplodedNodeSet dstPrevisit; 135 getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred, 136 msg, *this); 137 138 // Proceed with evaluate the message expression. 139 ExplodedNodeSet dstEval; 140 141 for (ExplodedNodeSet::iterator DI = dstPrevisit.begin(), 142 DE = dstPrevisit.end(); DI != DE; ++DI) { 143 144 ExplodedNode *Pred = *DI; 145 bool RaisesException = false; 146 SaveAndRestore<bool> OldSink(Builder->BuildSinks); 147 SaveOr OldHasGen(Builder->hasGeneratedNode); 148 149 if (const Expr *Receiver = msg.getInstanceReceiver()) { 150 const ProgramState *state = Pred->getState(); 151 SVal recVal = state->getSVal(Receiver); 152 if (!recVal.isUndef()) { 153 // Bifurcate the state into nil and non-nil ones. 154 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 155 156 const ProgramState *notNilState, *nilState; 157 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 158 159 // There are three cases: can be nil or non-nil, must be nil, must be 160 // non-nil. We ignore must be nil, and merge the rest two into non-nil. 161 if (nilState && !notNilState) { 162 dstEval.insert(Pred); 163 continue; 164 } 165 166 // Check if the "raise" message was sent. 167 assert(notNilState); 168 if (msg.getSelector() == RaiseSel) 169 RaisesException = true; 170 171 // Check if we raise an exception. For now treat these as sinks. 172 // Eventually we will want to handle exceptions properly. 173 if (RaisesException) 174 Builder->BuildSinks = true; 175 176 // Dispatch to plug-in transfer function. 177 evalObjCMessage(dstEval, msg, Pred, notNilState); 178 } 179 } 180 else if (const ObjCInterfaceDecl *Iface = msg.getReceiverInterface()) { 181 IdentifierInfo* ClsName = Iface->getIdentifier(); 182 Selector S = msg.getSelector(); 183 184 // Check for special instance methods. 185 if (!NSExceptionII) { 186 ASTContext &Ctx = getContext(); 187 NSExceptionII = &Ctx.Idents.get("NSException"); 188 } 189 190 if (ClsName == NSExceptionII) { 191 enum { NUM_RAISE_SELECTORS = 2 }; 192 193 // Lazily create a cache of the selectors. 194 if (!NSExceptionInstanceRaiseSelectors) { 195 ASTContext &Ctx = getContext(); 196 NSExceptionInstanceRaiseSelectors = 197 new Selector[NUM_RAISE_SELECTORS]; 198 SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II; 199 unsigned idx = 0; 200 201 // raise:format: 202 II.push_back(&Ctx.Idents.get("raise")); 203 II.push_back(&Ctx.Idents.get("format")); 204 NSExceptionInstanceRaiseSelectors[idx++] = 205 Ctx.Selectors.getSelector(II.size(), &II[0]); 206 207 // raise:format::arguments: 208 II.push_back(&Ctx.Idents.get("arguments")); 209 NSExceptionInstanceRaiseSelectors[idx++] = 210 Ctx.Selectors.getSelector(II.size(), &II[0]); 211 } 212 213 for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i) 214 if (S == NSExceptionInstanceRaiseSelectors[i]) { 215 RaisesException = true; 216 break; 217 } 218 } 219 220 // Check if we raise an exception. For now treat these as sinks. 221 // Eventually we will want to handle exceptions properly. 222 if (RaisesException) 223 Builder->BuildSinks = true; 224 225 // Dispatch to plug-in transfer function. 226 evalObjCMessage(dstEval, msg, Pred, Pred->getState()); 227 } 228 229 assert(Builder->BuildSinks || Builder->hasGeneratedNode); 230 } 231 232 // Finally, perform the post-condition check of the ObjCMessageExpr and store 233 // the created nodes in 'Dst'. 234 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstEval, msg, *this); 235} 236 237void ExprEngine::evalObjCMessage(ExplodedNodeSet &Dst, const ObjCMessage &msg, 238 ExplodedNode *Pred, 239 const ProgramState *state) { 240 assert (Builder && "StmtNodeBuilder must be defined."); 241 242 // First handle the return value. 243 SVal ReturnValue = UnknownVal(); 244 245 // Some method families have known return values. 246 switch (msg.getMethodFamily()) { 247 default: 248 break; 249 case OMF_autorelease: 250 case OMF_retain: 251 case OMF_self: { 252 // These methods return their receivers. 253 const Expr *ReceiverE = msg.getInstanceReceiver(); 254 if (ReceiverE) 255 ReturnValue = state->getSVal(ReceiverE); 256 break; 257 } 258 } 259 260 // If we failed to figure out the return value, use a conjured value instead. 261 if (ReturnValue.isUnknown()) { 262 SValBuilder &SVB = getSValBuilder(); 263 QualType ResultTy = msg.getResultType(getContext()); 264 unsigned Count = Builder->getCurrentBlockCount(); 265 const Expr *CurrentE = cast<Expr>(currentStmt); 266 ReturnValue = SVB.getConjuredSymbolVal(NULL, CurrentE, ResultTy, Count); 267 } 268 269 // Bind the return value. 270 state = state->BindExpr(currentStmt, ReturnValue); 271 272 // Invalidate the arguments (and the receiver) 273 const LocationContext *LC = Pred->getLocationContext(); 274 state = invalidateArguments(state, CallOrObjCMessage(msg, state), LC); 275 276 // And create the new node. 277 MakeNode(Dst, msg.getOriginExpr(), Pred, state); 278} 279 280