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/AST/StmtObjC.h" 15 #include "clang/StaticAnalyzer/Core/CheckerManager.h" 16 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" 17 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 18 19 using namespace clang; 20 using namespace ento; 21 22 void ExprEngine::VisitLvalObjCIvarRefExpr(const ObjCIvarRefExpr *Ex, 23 ExplodedNode *Pred, 24 ExplodedNodeSet &Dst) { 25 ProgramStateRef state = Pred->getState(); 26 const LocationContext *LCtx = Pred->getLocationContext(); 27 SVal baseVal = state->getSVal(Ex->getBase(), LCtx); 28 SVal location = state->getLValue(Ex->getDecl(), baseVal); 29 30 ExplodedNodeSet dstIvar; 31 StmtNodeBuilder Bldr(Pred, dstIvar, *currBldrCtx); 32 Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, location)); 33 34 // Perform the post-condition check of the ObjCIvarRefExpr and store 35 // the created nodes in 'Dst'. 36 getCheckerManager().runCheckersForPostStmt(Dst, dstIvar, Ex, *this); 37 } 38 39 void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S, 40 ExplodedNode *Pred, 41 ExplodedNodeSet &Dst) { 42 getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this); 43 } 44 45 void ExprEngine::VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S, 46 ExplodedNode *Pred, 47 ExplodedNodeSet &Dst) { 48 49 // ObjCForCollectionStmts are processed in two places. This method 50 // handles the case where an ObjCForCollectionStmt* occurs as one of the 51 // statements within a basic block. This transfer function does two things: 52 // 53 // (1) binds the next container value to 'element'. This creates a new 54 // node in the ExplodedGraph. 55 // 56 // (2) binds the value 0/1 to the ObjCForCollectionStmt* itself, indicating 57 // whether or not the container has any more elements. This value 58 // will be tested in ProcessBranch. We need to explicitly bind 59 // this value because a container can contain nil elements. 60 // 61 // FIXME: Eventually this logic should actually do dispatches to 62 // 'countByEnumeratingWithState:objects:count:' (NSFastEnumeration). 63 // This will require simulating a temporary NSFastEnumerationState, either 64 // through an SVal or through the use of MemRegions. This value can 65 // be affixed to the ObjCForCollectionStmt* instead of 0/1; when the loop 66 // terminates we reclaim the temporary (it goes out of scope) and we 67 // we can test if the SVal is 0 or if the MemRegion is null (depending 68 // on what approach we take). 69 // 70 // For now: simulate (1) by assigning either a symbol or nil if the 71 // container is empty. Thus this transfer function will by default 72 // result in state splitting. 73 74 const Stmt *elem = S->getElement(); 75 ProgramStateRef state = Pred->getState(); 76 SVal elementV; 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 evalLocation(dstLocation, S, elem, Pred, state, elementV, NULL, false); 89 90 ExplodedNodeSet Tmp; 91 StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx); 92 93 for (ExplodedNodeSet::iterator NI = dstLocation.begin(), 94 NE = dstLocation.end(); NI!=NE; ++NI) { 95 Pred = *NI; 96 ProgramStateRef state = Pred->getState(); 97 const LocationContext *LCtx = Pred->getLocationContext(); 98 99 // Handle the case where the container still has elements. 100 SVal TrueV = svalBuilder.makeTruthVal(1); 101 ProgramStateRef hasElems = state->BindExpr(S, LCtx, TrueV); 102 103 // Handle the case where the container has no elements. 104 SVal FalseV = svalBuilder.makeTruthVal(0); 105 ProgramStateRef noElems = state->BindExpr(S, LCtx, FalseV); 106 107 if (loc::MemRegionVal *MV = dyn_cast<loc::MemRegionVal>(&elementV)) 108 if (const TypedValueRegion *R = 109 dyn_cast<TypedValueRegion>(MV->getRegion())) { 110 // FIXME: The proper thing to do is to really iterate over the 111 // container. We will do this with dispatch logic to the store. 112 // For now, just 'conjure' up a symbolic value. 113 QualType T = R->getValueType(); 114 assert(Loc::isLocType(T)); 115 SymbolRef Sym = SymMgr.conjureSymbol(elem, LCtx, T, 116 currBldrCtx->blockCount()); 117 SVal V = svalBuilder.makeLoc(Sym); 118 hasElems = hasElems->bindLoc(elementV, V); 119 120 // Bind the location to 'nil' on the false branch. 121 SVal nilV = svalBuilder.makeIntVal(0, T); 122 noElems = noElems->bindLoc(elementV, nilV); 123 } 124 125 // Create the new nodes. 126 Bldr.generateNode(S, Pred, hasElems); 127 Bldr.generateNode(S, Pred, noElems); 128 } 129 130 // Finally, run any custom checkers. 131 // FIXME: Eventually all pre- and post-checks should live in VisitStmt. 132 getCheckerManager().runCheckersForPostStmt(Dst, Tmp, S, *this); 133 } 134 135 static bool isSubclass(const ObjCInterfaceDecl *Class, IdentifierInfo *II) { 136 if (!Class) 137 return false; 138 if (Class->getIdentifier() == II) 139 return true; 140 return isSubclass(Class->getSuperClass(), II); 141 } 142 143 void ExprEngine::VisitObjCMessage(const ObjCMessageExpr *ME, 144 ExplodedNode *Pred, 145 ExplodedNodeSet &Dst) { 146 CallEventManager &CEMgr = getStateManager().getCallEventManager(); 147 CallEventRef<ObjCMethodCall> Msg = 148 CEMgr.getObjCMethodCall(ME, Pred->getState(), Pred->getLocationContext()); 149 150 // Handle the previsits checks. 151 ExplodedNodeSet dstPrevisit; 152 getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred, 153 *Msg, *this); 154 ExplodedNodeSet dstGenericPrevisit; 155 getCheckerManager().runCheckersForPreCall(dstGenericPrevisit, dstPrevisit, 156 *Msg, *this); 157 158 // Proceed with evaluate the message expression. 159 ExplodedNodeSet dstEval; 160 StmtNodeBuilder Bldr(dstGenericPrevisit, dstEval, *currBldrCtx); 161 162 for (ExplodedNodeSet::iterator DI = dstGenericPrevisit.begin(), 163 DE = dstGenericPrevisit.end(); DI != DE; ++DI) { 164 ExplodedNode *Pred = *DI; 165 ProgramStateRef State = Pred->getState(); 166 CallEventRef<ObjCMethodCall> UpdatedMsg = Msg.cloneWithState(State); 167 168 if (UpdatedMsg->isInstanceMessage()) { 169 SVal recVal = UpdatedMsg->getReceiverSVal(); 170 if (!recVal.isUndef()) { 171 // Bifurcate the state into nil and non-nil ones. 172 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 173 174 ProgramStateRef notNilState, nilState; 175 llvm::tie(notNilState, nilState) = State->assume(receiverVal); 176 177 // There are three cases: can be nil or non-nil, must be nil, must be 178 // non-nil. We ignore must be nil, and merge the rest two into non-nil. 179 // FIXME: This ignores many potential bugs (<rdar://problem/11733396>). 180 // Revisit once we have lazier constraints. 181 if (nilState && !notNilState) { 182 continue; 183 } 184 185 // Check if the "raise" message was sent. 186 assert(notNilState); 187 if (Msg->getSelector() == RaiseSel) { 188 // If we raise an exception, for now treat it as a sink. 189 // Eventually we will want to handle exceptions properly. 190 Bldr.generateSink(currStmt, Pred, State); 191 continue; 192 } 193 194 // Generate a transition to non-Nil state. 195 if (notNilState != State) { 196 Pred = Bldr.generateNode(currStmt, Pred, notNilState); 197 assert(Pred && "Should have cached out already!"); 198 } 199 } 200 } else { 201 // Check for special class methods. 202 if (const ObjCInterfaceDecl *Iface = Msg->getReceiverInterface()) { 203 if (!NSExceptionII) { 204 ASTContext &Ctx = getContext(); 205 NSExceptionII = &Ctx.Idents.get("NSException"); 206 } 207 208 if (isSubclass(Iface, NSExceptionII)) { 209 enum { NUM_RAISE_SELECTORS = 2 }; 210 211 // Lazily create a cache of the selectors. 212 if (!NSExceptionInstanceRaiseSelectors) { 213 ASTContext &Ctx = getContext(); 214 NSExceptionInstanceRaiseSelectors = 215 new Selector[NUM_RAISE_SELECTORS]; 216 SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II; 217 unsigned idx = 0; 218 219 // raise:format: 220 II.push_back(&Ctx.Idents.get("raise")); 221 II.push_back(&Ctx.Idents.get("format")); 222 NSExceptionInstanceRaiseSelectors[idx++] = 223 Ctx.Selectors.getSelector(II.size(), &II[0]); 224 225 // raise:format:arguments: 226 II.push_back(&Ctx.Idents.get("arguments")); 227 NSExceptionInstanceRaiseSelectors[idx++] = 228 Ctx.Selectors.getSelector(II.size(), &II[0]); 229 } 230 231 Selector S = Msg->getSelector(); 232 bool RaisesException = false; 233 for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i) { 234 if (S == NSExceptionInstanceRaiseSelectors[i]) { 235 RaisesException = true; 236 break; 237 } 238 } 239 if (RaisesException) { 240 // If we raise an exception, for now treat it as a sink. 241 // Eventually we will want to handle exceptions properly. 242 Bldr.generateSink(currStmt, Pred, Pred->getState()); 243 continue; 244 } 245 246 } 247 } 248 } 249 250 defaultEvalCall(Bldr, Pred, *UpdatedMsg); 251 } 252 253 ExplodedNodeSet dstPostvisit; 254 getCheckerManager().runCheckersForPostCall(dstPostvisit, dstEval, 255 *Msg, *this); 256 257 // Finally, perform the post-condition check of the ObjCMessageExpr and store 258 // the created nodes in 'Dst'. 259 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstPostvisit, 260 *Msg, *this); 261 } 262
