ExprEngineObjC.cpp revision 96479da6ad9d921d875e7be29fe1bfa127be8069
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/Calls.h" 17#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 18 19using namespace clang; 20using namespace ento; 21 22void 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, *currentBuilderContext); 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 39void ExprEngine::VisitObjCAtSynchronizedStmt(const ObjCAtSynchronizedStmt *S, 40 ExplodedNode *Pred, 41 ExplodedNodeSet &Dst) { 42 getCheckerManager().runCheckersForPreStmt(Dst, Pred, S, *this); 43} 44 45void 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, *currentBuilderContext); 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 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 116 SymbolRef Sym = SymMgr.getConjuredSymbol(elem, LCtx, T, Count); 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 135static 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 143void ExprEngine::VisitObjCMessage(const ObjCMethodCall &msg, 144 ExplodedNode *Pred, 145 ExplodedNodeSet &Dst) { 146 147 // Handle the previsits checks. 148 ExplodedNodeSet dstPrevisit; 149 getCheckerManager().runCheckersForPreObjCMessage(dstPrevisit, Pred, 150 msg, *this); 151 ExplodedNodeSet dstGenericPrevisit; 152 getCheckerManager().runCheckersForPreCall(dstGenericPrevisit, dstPrevisit, 153 msg, *this); 154 155 // Proceed with evaluate the message expression. 156 ExplodedNodeSet dstEval; 157 StmtNodeBuilder Bldr(dstGenericPrevisit, dstEval, *currentBuilderContext); 158 159 for (ExplodedNodeSet::iterator DI = dstGenericPrevisit.begin(), 160 DE = dstGenericPrevisit.end(); DI != DE; ++DI) { 161 162 ExplodedNode *Pred = *DI; 163 bool RaisesException = false; 164 165 if (msg.isInstanceMessage()) { 166 SVal recVal = msg.getReceiverSVal(); 167 if (!recVal.isUndef()) { 168 // Bifurcate the state into nil and non-nil ones. 169 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 170 171 ProgramStateRef state = Pred->getState(); 172 ProgramStateRef notNilState, nilState; 173 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 174 175 // There are three cases: can be nil or non-nil, must be nil, must be 176 // non-nil. We ignore must be nil, and merge the rest two into non-nil. 177 // FIXME: This ignores many potential bugs (<rdar://problem/11733396>). 178 // Revisit once we have lazier constraints. 179 if (nilState && !notNilState) { 180 continue; 181 } 182 183 // Check if the "raise" message was sent. 184 assert(notNilState); 185 if (msg.getSelector() == RaiseSel) 186 RaisesException = true; 187 188 // If we raise an exception, for now treat it as a sink. 189 // Eventually we will want to handle exceptions properly. 190 // Dispatch to plug-in transfer function. 191 evalObjCMessage(Bldr, msg, Pred, notNilState, RaisesException); 192 } 193 } else { 194 // Check for special class methods. 195 if (const ObjCInterfaceDecl *Iface = msg.getReceiverInterface()) { 196 if (!NSExceptionII) { 197 ASTContext &Ctx = getContext(); 198 NSExceptionII = &Ctx.Idents.get("NSException"); 199 } 200 201 if (isSubclass(Iface, NSExceptionII)) { 202 enum { NUM_RAISE_SELECTORS = 2 }; 203 204 // Lazily create a cache of the selectors. 205 if (!NSExceptionInstanceRaiseSelectors) { 206 ASTContext &Ctx = getContext(); 207 NSExceptionInstanceRaiseSelectors = 208 new Selector[NUM_RAISE_SELECTORS]; 209 SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II; 210 unsigned idx = 0; 211 212 // raise:format: 213 II.push_back(&Ctx.Idents.get("raise")); 214 II.push_back(&Ctx.Idents.get("format")); 215 NSExceptionInstanceRaiseSelectors[idx++] = 216 Ctx.Selectors.getSelector(II.size(), &II[0]); 217 218 // raise:format:arguments: 219 II.push_back(&Ctx.Idents.get("arguments")); 220 NSExceptionInstanceRaiseSelectors[idx++] = 221 Ctx.Selectors.getSelector(II.size(), &II[0]); 222 } 223 224 Selector S = msg.getSelector(); 225 for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i) { 226 if (S == NSExceptionInstanceRaiseSelectors[i]) { 227 RaisesException = true; 228 break; 229 } 230 } 231 } 232 } 233 234 // If we raise an exception, for now treat it as a sink. 235 // Eventually we will want to handle exceptions properly. 236 // Dispatch to plug-in transfer function. 237 evalObjCMessage(Bldr, msg, Pred, Pred->getState(), RaisesException); 238 } 239 } 240 241 ExplodedNodeSet dstPostvisit; 242 getCheckerManager().runCheckersForPostCall(dstPostvisit, dstEval, msg, *this); 243 244 // Finally, perform the post-condition check of the ObjCMessageExpr and store 245 // the created nodes in 'Dst'. 246 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstPostvisit, 247 msg, *this); 248} 249 250void ExprEngine::evalObjCMessage(StmtNodeBuilder &Bldr, 251 const ObjCMethodCall &msg, 252 ExplodedNode *Pred, 253 ProgramStateRef state, 254 bool GenSink) { 255 // First handle the return value. 256 SVal ReturnValue = UnknownVal(); 257 258 // Some method families have known return values. 259 switch (msg.getMethodFamily()) { 260 default: 261 break; 262 case OMF_autorelease: 263 case OMF_retain: 264 case OMF_self: { 265 // These methods return their receivers. 266 ReturnValue = msg.getReceiverSVal(); 267 break; 268 } 269 } 270 271 const LocationContext *LCtx = Pred->getLocationContext(); 272 unsigned BlockCount = currentBuilderContext->getCurrentBlockCount(); 273 274 // If we failed to figure out the return value, use a conjured value instead. 275 if (ReturnValue.isUnknown()) { 276 SValBuilder &SVB = getSValBuilder(); 277 QualType ResultTy = msg.getResultType(); 278 const Expr *CurrentE = cast<Expr>(currentStmt); 279 ReturnValue = SVB.getConjuredSymbolVal(NULL, CurrentE, LCtx, ResultTy, 280 BlockCount); 281 } 282 283 // Bind the return value. 284 state = state->BindExpr(currentStmt, LCtx, ReturnValue); 285 286 // Invalidate the arguments (and the receiver) 287 state = msg.invalidateRegions(BlockCount, state); 288 289 // And create the new node. 290 Bldr.generateNode(currentStmt, Pred, state, GenSink); 291 assert(Bldr.hasGeneratedNodes()); 292} 293 294