ExprEngineObjC.cpp revision 8bef8238181a30e52dea380789a7e2d760eac532
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 18using namespace clang; 19using namespace ento; 20 21void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex, 22 ExplodedNode *Pred, 23 ExplodedNodeSet &Dst) { 24 ProgramStateRef state = Pred->getState(); 25 const LocationContext *LCtx = Pred->getLocationContext(); 26 SVal baseVal = state->getSVal(Ex->getBase(), LCtx); 27 SVal location = state->getLValue(Ex->getDecl(), baseVal); 28 29 ExplodedNodeSet dstIvar; 30 StmtNodeBuilder Bldr(Pred, dstIvar, *currentBuilderContext); 31 Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, 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 ProgramStateRef state = Pred->getState(); 75 SVal elementV; 76 StmtNodeBuilder Bldr(Pred, Dst, *currentBuilderContext); 77 78 if (const DeclStmt *DS = dyn_cast<DeclStmt>(elem)) { 79 const VarDecl *elemD = cast<VarDecl>(DS->getSingleDecl()); 80 assert(elemD->getInit() == 0); 81 elementV = state->getLValue(elemD, Pred->getLocationContext()); 82 } 83 else { 84 elementV = state->getSVal(elem, Pred->getLocationContext()); 85 } 86 87 ExplodedNodeSet dstLocation; 88 Bldr.takeNodes(Pred); 89 evalLocation(dstLocation, elem, Pred, state, elementV, NULL, false); 90 Bldr.addNodes(dstLocation); 91 92 for (ExplodedNodeSet::iterator NI = dstLocation.begin(), 93 NE = dstLocation.end(); NI!=NE; ++NI) { 94 Pred = *NI; 95 ProgramStateRef state = Pred->getState(); 96 const LocationContext *LCtx = Pred->getLocationContext(); 97 98 // Handle the case where the container still has elements. 99 SVal TrueV = svalBuilder.makeTruthVal(1); 100 ProgramStateRef hasElems = state->BindExpr(S, LCtx, TrueV); 101 102 // Handle the case where the container has no elements. 103 SVal FalseV = svalBuilder.makeTruthVal(0); 104 ProgramStateRef noElems = state->BindExpr(S, LCtx, FalseV); 105 106 if (loc::MemRegionVal *MV = dyn_cast<loc::MemRegionVal>(&elementV)) 107 if (const TypedValueRegion *R = 108 dyn_cast<TypedValueRegion>(MV->getRegion())) { 109 // FIXME: The proper thing to do is to really iterate over the 110 // container. We will do this with dispatch logic to the store. 111 // For now, just 'conjure' up a symbolic value. 112 QualType T = R->getValueType(); 113 assert(Loc::isLocType(T)); 114 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 115 SymbolRef Sym = SymMgr.getConjuredSymbol(elem, T, Count); 116 SVal V = svalBuilder.makeLoc(Sym); 117 hasElems = hasElems->bindLoc(elementV, V); 118 119 // Bind the location to 'nil' on the false branch. 120 SVal nilV = svalBuilder.makeIntVal(0, T); 121 noElems = noElems->bindLoc(elementV, nilV); 122 } 123 124 // Create the new nodes. 125 Bldr.generateNode(S, Pred, hasElems); 126 Bldr.generateNode(S, Pred, noElems); 127 } 128} 129 130void ExprEngine::VisitObjCMessage(const ObjCMessage &msg, 131 ExplodedNode *Pred, 132 ExplodedNodeSet &Dst) { 133 134 // Handle the previsits checks. 135 ExplodedNodeSet dstPrevisit; 136 getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred, 137 msg, *this); 138 139 // Proceed with evaluate the message expression. 140 ExplodedNodeSet dstEval; 141 StmtNodeBuilder Bldr(dstPrevisit, dstEval, *currentBuilderContext); 142 143 for (ExplodedNodeSet::iterator DI = dstPrevisit.begin(), 144 DE = dstPrevisit.end(); DI != DE; ++DI) { 145 146 ExplodedNode *Pred = *DI; 147 bool RaisesException = false; 148 149 if (const Expr *Receiver = msg.getInstanceReceiver()) { 150 ProgramStateRef state = Pred->getState(); 151 SVal recVal = state->getSVal(Receiver, Pred->getLocationContext()); 152 if (!recVal.isUndef()) { 153 // Bifurcate the state into nil and non-nil ones. 154 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 155 156 ProgramStateRef 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 continue; 163 } 164 165 // Check if the "raise" message was sent. 166 assert(notNilState); 167 if (msg.getSelector() == RaiseSel) 168 RaisesException = true; 169 170 // If we raise an exception, for now treat it as a sink. 171 // Eventually we will want to handle exceptions properly. 172 // Dispatch to plug-in transfer function. 173 evalObjCMessage(Bldr, msg, Pred, notNilState, RaisesException); 174 } 175 } 176 else if (const ObjCInterfaceDecl *Iface = msg.getReceiverInterface()) { 177 IdentifierInfo* ClsName = Iface->getIdentifier(); 178 Selector S = msg.getSelector(); 179 180 // Check for special instance methods. 181 if (!NSExceptionII) { 182 ASTContext &Ctx = getContext(); 183 NSExceptionII = &Ctx.Idents.get("NSException"); 184 } 185 186 if (ClsName == NSExceptionII) { 187 enum { NUM_RAISE_SELECTORS = 2 }; 188 189 // Lazily create a cache of the selectors. 190 if (!NSExceptionInstanceRaiseSelectors) { 191 ASTContext &Ctx = getContext(); 192 NSExceptionInstanceRaiseSelectors = 193 new Selector[NUM_RAISE_SELECTORS]; 194 SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II; 195 unsigned idx = 0; 196 197 // raise:format: 198 II.push_back(&Ctx.Idents.get("raise")); 199 II.push_back(&Ctx.Idents.get("format")); 200 NSExceptionInstanceRaiseSelectors[idx++] = 201 Ctx.Selectors.getSelector(II.size(), &II[0]); 202 203 // raise:format::arguments: 204 II.push_back(&Ctx.Idents.get("arguments")); 205 NSExceptionInstanceRaiseSelectors[idx++] = 206 Ctx.Selectors.getSelector(II.size(), &II[0]); 207 } 208 209 for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i) 210 if (S == NSExceptionInstanceRaiseSelectors[i]) { 211 RaisesException = true; 212 break; 213 } 214 } 215 216 // If we raise an exception, for now treat it as a sink. 217 // Eventually we will want to handle exceptions properly. 218 // Dispatch to plug-in transfer function. 219 evalObjCMessage(Bldr, msg, Pred, Pred->getState(), RaisesException); 220 } 221 } 222 223 // Finally, perform the post-condition check of the ObjCMessageExpr and store 224 // the created nodes in 'Dst'. 225 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstEval, msg, *this); 226} 227 228void ExprEngine::evalObjCMessage(StmtNodeBuilder &Bldr, 229 const ObjCMessage &msg, 230 ExplodedNode *Pred, 231 ProgramStateRef state, 232 bool GenSink) { 233 // First handle the return value. 234 SVal ReturnValue = UnknownVal(); 235 236 // Some method families have known return values. 237 switch (msg.getMethodFamily()) { 238 default: 239 break; 240 case OMF_autorelease: 241 case OMF_retain: 242 case OMF_self: { 243 // These methods return their receivers. 244 const Expr *ReceiverE = msg.getInstanceReceiver(); 245 if (ReceiverE) 246 ReturnValue = state->getSVal(ReceiverE, Pred->getLocationContext()); 247 break; 248 } 249 } 250 251 // If we failed to figure out the return value, use a conjured value instead. 252 if (ReturnValue.isUnknown()) { 253 SValBuilder &SVB = getSValBuilder(); 254 QualType ResultTy = msg.getResultType(getContext()); 255 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 256 const Expr *CurrentE = cast<Expr>(currentStmt); 257 ReturnValue = SVB.getConjuredSymbolVal(NULL, CurrentE, ResultTy, Count); 258 } 259 260 // Bind the return value. 261 const LocationContext *LCtx = Pred->getLocationContext(); 262 state = state->BindExpr(currentStmt, LCtx, ReturnValue); 263 264 // Invalidate the arguments (and the receiver) 265 state = invalidateArguments(state, CallOrObjCMessage(msg, state, LCtx), LCtx); 266 267 // And create the new node. 268 Bldr.generateNode(msg.getOriginExpr(), Pred, state, GenSink); 269 assert(Bldr.hasGeneratedNodes()); 270} 271 272