ExprEngineObjC.cpp revision e81ce256b62717dd846bd19aecc4115a0dcd4995
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 ExplodedNode *Pred = *DI; 162 163 if (msg.isInstanceMessage()) { 164 SVal recVal = msg.getReceiverSVal(); 165 if (!recVal.isUndef()) { 166 // Bifurcate the state into nil and non-nil ones. 167 DefinedOrUnknownSVal receiverVal = cast<DefinedOrUnknownSVal>(recVal); 168 169 ProgramStateRef state = Pred->getState(); 170 ProgramStateRef notNilState, nilState; 171 llvm::tie(notNilState, nilState) = state->assume(receiverVal); 172 173 // There are three cases: can be nil or non-nil, must be nil, must be 174 // non-nil. We ignore must be nil, and merge the rest two into non-nil. 175 // FIXME: This ignores many potential bugs (<rdar://problem/11733396>). 176 // Revisit once we have lazier constraints. 177 if (nilState && !notNilState) { 178 continue; 179 } 180 181 // Check if the "raise" message was sent. 182 assert(notNilState); 183 if (msg.getSelector() == RaiseSel) { 184 // If we raise an exception, for now treat it as a sink. 185 // Eventually we will want to handle exceptions properly. 186 Bldr.generateNode(currentStmt, Pred, Pred->getState(), true); 187 continue; 188 } 189 190 // Generate a transition to non-Nil state. 191 if (notNilState != state) 192 Pred = Bldr.generateNode(currentStmt, Pred, notNilState); 193 194 // Evaluate the call. 195 defaultEvalCall(Bldr, Pred, msg); 196 } 197 } else { 198 // Check for special class methods. 199 if (const ObjCInterfaceDecl *Iface = msg.getReceiverInterface()) { 200 if (!NSExceptionII) { 201 ASTContext &Ctx = getContext(); 202 NSExceptionII = &Ctx.Idents.get("NSException"); 203 } 204 205 if (isSubclass(Iface, NSExceptionII)) { 206 enum { NUM_RAISE_SELECTORS = 2 }; 207 208 // Lazily create a cache of the selectors. 209 if (!NSExceptionInstanceRaiseSelectors) { 210 ASTContext &Ctx = getContext(); 211 NSExceptionInstanceRaiseSelectors = 212 new Selector[NUM_RAISE_SELECTORS]; 213 SmallVector<IdentifierInfo*, NUM_RAISE_SELECTORS> II; 214 unsigned idx = 0; 215 216 // raise:format: 217 II.push_back(&Ctx.Idents.get("raise")); 218 II.push_back(&Ctx.Idents.get("format")); 219 NSExceptionInstanceRaiseSelectors[idx++] = 220 Ctx.Selectors.getSelector(II.size(), &II[0]); 221 222 // raise:format:arguments: 223 II.push_back(&Ctx.Idents.get("arguments")); 224 NSExceptionInstanceRaiseSelectors[idx++] = 225 Ctx.Selectors.getSelector(II.size(), &II[0]); 226 } 227 228 Selector S = msg.getSelector(); 229 bool RaisesException = false; 230 for (unsigned i = 0; i < NUM_RAISE_SELECTORS; ++i) { 231 if (S == NSExceptionInstanceRaiseSelectors[i]) { 232 RaisesException = true; 233 break; 234 } 235 } 236 if (RaisesException) { 237 // If we raise an exception, for now treat it as a sink. 238 // Eventually we will want to handle exceptions properly. 239 Bldr.generateNode(currentStmt, Pred, Pred->getState(), true); 240 continue; 241 } 242 243 } 244 } 245 246 // Evaluate the call. 247 defaultEvalCall(Bldr, Pred, msg); 248 } 249 } 250 251 ExplodedNodeSet dstPostvisit; 252 getCheckerManager().runCheckersForPostCall(dstPostvisit, dstEval, msg, *this); 253 254 // Finally, perform the post-condition check of the ObjCMessageExpr and store 255 // the created nodes in 'Dst'. 256 getCheckerManager().runCheckersForPostObjCMessage(Dst, dstPostvisit, 257 msg, *this); 258} 259