1//===- Store.cpp - Interface for maps from Locations to Values ------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file defined the types Store and StoreManager. 10// 11//===----------------------------------------------------------------------===// 12 13#include "clang/StaticAnalyzer/Core/PathSensitive/Store.h" 14#include "clang/AST/ASTContext.h" 15#include "clang/AST/CXXInheritance.h" 16#include "clang/AST/CharUnits.h" 17#include "clang/AST/Decl.h" 18#include "clang/AST/DeclCXX.h" 19#include "clang/AST/DeclObjC.h" 20#include "clang/AST/Expr.h" 21#include "clang/AST/Type.h" 22#include "clang/Basic/LLVM.h" 23#include "clang/StaticAnalyzer/Core/PathSensitive/BasicValueFactory.h" 24#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" 25#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h" 26#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 27#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h" 28#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h" 29#include "clang/StaticAnalyzer/Core/PathSensitive/StoreRef.h" 30#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h" 31#include "llvm/ADT/APSInt.h" 32#include "llvm/ADT/Optional.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/Support/Casting.h" 35#include "llvm/Support/ErrorHandling.h" 36#include <cassert> 37#include <cstdint> 38 39using namespace clang; 40using namespace ento; 41 42StoreManager::StoreManager(ProgramStateManager &stateMgr) 43 : svalBuilder(stateMgr.getSValBuilder()), StateMgr(stateMgr), 44 MRMgr(svalBuilder.getRegionManager()), Ctx(stateMgr.getContext()) {} 45 46StoreRef StoreManager::enterStackFrame(Store OldStore, 47 const CallEvent &Call, 48 const StackFrameContext *LCtx) { 49 StoreRef Store = StoreRef(OldStore, *this); 50 51 SmallVector<CallEvent::FrameBindingTy, 16> InitialBindings; 52 Call.getInitialStackFrameContents(LCtx, InitialBindings); 53 54 for (const auto &I : InitialBindings) 55 Store = Bind(Store.getStore(), I.first.castAs<Loc>(), I.second); 56 57 return Store; 58} 59 60const ElementRegion *StoreManager::MakeElementRegion(const SubRegion *Base, 61 QualType EleTy, 62 uint64_t index) { 63 NonLoc idx = svalBuilder.makeArrayIndex(index); 64 return MRMgr.getElementRegion(EleTy, idx, Base, svalBuilder.getContext()); 65} 66 67const ElementRegion *StoreManager::GetElementZeroRegion(const SubRegion *R, 68 QualType T) { 69 NonLoc idx = svalBuilder.makeZeroArrayIndex(); 70 assert(!T.isNull()); 71 return MRMgr.getElementRegion(T, idx, R, Ctx); 72} 73 74const MemRegion *StoreManager::castRegion(const MemRegion *R, QualType CastToTy) { 75 ASTContext &Ctx = StateMgr.getContext(); 76 77 // Handle casts to Objective-C objects. 78 if (CastToTy->isObjCObjectPointerType()) 79 return R->StripCasts(); 80 81 if (CastToTy->isBlockPointerType()) { 82 // FIXME: We may need different solutions, depending on the symbol 83 // involved. Blocks can be casted to/from 'id', as they can be treated 84 // as Objective-C objects. This could possibly be handled by enhancing 85 // our reasoning of downcasts of symbolic objects. 86 if (isa<CodeTextRegion>(R) || isa<SymbolicRegion>(R)) 87 return R; 88 89 // We don't know what to make of it. Return a NULL region, which 90 // will be interpreted as UnknownVal. 91 return nullptr; 92 } 93 94 // Now assume we are casting from pointer to pointer. Other cases should 95 // already be handled. 96 QualType PointeeTy = CastToTy->getPointeeType(); 97 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy); 98 99 // Handle casts to void*. We just pass the region through. 100 if (CanonPointeeTy.getLocalUnqualifiedType() == Ctx.VoidTy) 101 return R; 102 103 // Handle casts from compatible types. 104 if (R->isBoundable()) 105 if (const auto *TR = dyn_cast<TypedValueRegion>(R)) { 106 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType()); 107 if (CanonPointeeTy == ObjTy) 108 return R; 109 } 110 111 // Process region cast according to the kind of the region being cast. 112 switch (R->getKind()) { 113 case MemRegion::CXXThisRegionKind: 114 case MemRegion::CodeSpaceRegionKind: 115 case MemRegion::StackLocalsSpaceRegionKind: 116 case MemRegion::StackArgumentsSpaceRegionKind: 117 case MemRegion::HeapSpaceRegionKind: 118 case MemRegion::UnknownSpaceRegionKind: 119 case MemRegion::StaticGlobalSpaceRegionKind: 120 case MemRegion::GlobalInternalSpaceRegionKind: 121 case MemRegion::GlobalSystemSpaceRegionKind: 122 case MemRegion::GlobalImmutableSpaceRegionKind: { 123 llvm_unreachable("Invalid region cast"); 124 } 125 126 case MemRegion::FunctionCodeRegionKind: 127 case MemRegion::BlockCodeRegionKind: 128 case MemRegion::BlockDataRegionKind: 129 case MemRegion::StringRegionKind: 130 // FIXME: Need to handle arbitrary downcasts. 131 case MemRegion::SymbolicRegionKind: 132 case MemRegion::AllocaRegionKind: 133 case MemRegion::CompoundLiteralRegionKind: 134 case MemRegion::FieldRegionKind: 135 case MemRegion::ObjCIvarRegionKind: 136 case MemRegion::ObjCStringRegionKind: 137 case MemRegion::VarRegionKind: 138 case MemRegion::CXXTempObjectRegionKind: 139 case MemRegion::CXXBaseObjectRegionKind: 140 case MemRegion::CXXDerivedObjectRegionKind: 141 return MakeElementRegion(cast<SubRegion>(R), PointeeTy); 142 143 case MemRegion::ElementRegionKind: { 144 // If we are casting from an ElementRegion to another type, the 145 // algorithm is as follows: 146 // 147 // (1) Compute the "raw offset" of the ElementRegion from the 148 // base region. This is done by calling 'getAsRawOffset()'. 149 // 150 // (2a) If we get a 'RegionRawOffset' after calling 151 // 'getAsRawOffset()', determine if the absolute offset 152 // can be exactly divided into chunks of the size of the 153 // casted-pointee type. If so, create a new ElementRegion with 154 // the pointee-cast type as the new ElementType and the index 155 // being the offset divded by the chunk size. If not, create 156 // a new ElementRegion at offset 0 off the raw offset region. 157 // 158 // (2b) If we don't a get a 'RegionRawOffset' after calling 159 // 'getAsRawOffset()', it means that we are at offset 0. 160 // 161 // FIXME: Handle symbolic raw offsets. 162 163 const ElementRegion *elementR = cast<ElementRegion>(R); 164 const RegionRawOffset &rawOff = elementR->getAsArrayOffset(); 165 const MemRegion *baseR = rawOff.getRegion(); 166 167 // If we cannot compute a raw offset, throw up our hands and return 168 // a NULL MemRegion*. 169 if (!baseR) 170 return nullptr; 171 172 CharUnits off = rawOff.getOffset(); 173 174 if (off.isZero()) { 175 // Edge case: we are at 0 bytes off the beginning of baseR. We 176 // check to see if type we are casting to is the same as the base 177 // region. If so, just return the base region. 178 if (const auto *TR = dyn_cast<TypedValueRegion>(baseR)) { 179 QualType ObjTy = Ctx.getCanonicalType(TR->getValueType()); 180 QualType CanonPointeeTy = Ctx.getCanonicalType(PointeeTy); 181 if (CanonPointeeTy == ObjTy) 182 return baseR; 183 } 184 185 // Otherwise, create a new ElementRegion at offset 0. 186 return MakeElementRegion(cast<SubRegion>(baseR), PointeeTy); 187 } 188 189 // We have a non-zero offset from the base region. We want to determine 190 // if the offset can be evenly divided by sizeof(PointeeTy). If so, 191 // we create an ElementRegion whose index is that value. Otherwise, we 192 // create two ElementRegions, one that reflects a raw offset and the other 193 // that reflects the cast. 194 195 // Compute the index for the new ElementRegion. 196 int64_t newIndex = 0; 197 const MemRegion *newSuperR = nullptr; 198 199 // We can only compute sizeof(PointeeTy) if it is a complete type. 200 if (!PointeeTy->isIncompleteType()) { 201 // Compute the size in **bytes**. 202 CharUnits pointeeTySize = Ctx.getTypeSizeInChars(PointeeTy); 203 if (!pointeeTySize.isZero()) { 204 // Is the offset a multiple of the size? If so, we can layer the 205 // ElementRegion (with elementType == PointeeTy) directly on top of 206 // the base region. 207 if (off % pointeeTySize == 0) { 208 newIndex = off / pointeeTySize; 209 newSuperR = baseR; 210 } 211 } 212 } 213 214 if (!newSuperR) { 215 // Create an intermediate ElementRegion to represent the raw byte. 216 // This will be the super region of the final ElementRegion. 217 newSuperR = MakeElementRegion(cast<SubRegion>(baseR), Ctx.CharTy, 218 off.getQuantity()); 219 } 220 221 return MakeElementRegion(cast<SubRegion>(newSuperR), PointeeTy, newIndex); 222 } 223 } 224 225 llvm_unreachable("unreachable"); 226} 227 228static bool regionMatchesCXXRecordType(SVal V, QualType Ty) { 229 const MemRegion *MR = V.getAsRegion(); 230 if (!MR) 231 return true; 232 233 const auto *TVR = dyn_cast<TypedValueRegion>(MR); 234 if (!TVR) 235 return true; 236 237 const CXXRecordDecl *RD = TVR->getValueType()->getAsCXXRecordDecl(); 238 if (!RD) 239 return true; 240 241 const CXXRecordDecl *Expected = Ty->getPointeeCXXRecordDecl(); 242 if (!Expected) 243 Expected = Ty->getAsCXXRecordDecl(); 244 245 return Expected->getCanonicalDecl() == RD->getCanonicalDecl(); 246} 247 248SVal StoreManager::evalDerivedToBase(SVal Derived, const CastExpr *Cast) { 249 // Sanity check to avoid doing the wrong thing in the face of 250 // reinterpret_cast. 251 if (!regionMatchesCXXRecordType(Derived, Cast->getSubExpr()->getType())) 252 return UnknownVal(); 253 254 // Walk through the cast path to create nested CXXBaseRegions. 255 SVal Result = Derived; 256 for (CastExpr::path_const_iterator I = Cast->path_begin(), 257 E = Cast->path_end(); 258 I != E; ++I) { 259 Result = evalDerivedToBase(Result, (*I)->getType(), (*I)->isVirtual()); 260 } 261 return Result; 262} 263 264SVal StoreManager::evalDerivedToBase(SVal Derived, const CXXBasePath &Path) { 265 // Walk through the path to create nested CXXBaseRegions. 266 SVal Result = Derived; 267 for (const auto &I : Path) 268 Result = evalDerivedToBase(Result, I.Base->getType(), 269 I.Base->isVirtual()); 270 return Result; 271} 272 273SVal StoreManager::evalDerivedToBase(SVal Derived, QualType BaseType, 274 bool IsVirtual) { 275 const MemRegion *DerivedReg = Derived.getAsRegion(); 276 if (!DerivedReg) 277 return Derived; 278 279 const CXXRecordDecl *BaseDecl = BaseType->getPointeeCXXRecordDecl(); 280 if (!BaseDecl) 281 BaseDecl = BaseType->getAsCXXRecordDecl(); 282 assert(BaseDecl && "not a C++ object?"); 283 284 if (const auto *AlreadyDerivedReg = 285 dyn_cast<CXXDerivedObjectRegion>(DerivedReg)) { 286 if (const auto *SR = 287 dyn_cast<SymbolicRegion>(AlreadyDerivedReg->getSuperRegion())) 288 if (SR->getSymbol()->getType()->getPointeeCXXRecordDecl() == BaseDecl) 289 return loc::MemRegionVal(SR); 290 291 DerivedReg = AlreadyDerivedReg->getSuperRegion(); 292 } 293 294 const MemRegion *BaseReg = MRMgr.getCXXBaseObjectRegion( 295 BaseDecl, cast<SubRegion>(DerivedReg), IsVirtual); 296 297 return loc::MemRegionVal(BaseReg); 298} 299 300/// Returns the static type of the given region, if it represents a C++ class 301/// object. 302/// 303/// This handles both fully-typed regions, where the dynamic type is known, and 304/// symbolic regions, where the dynamic type is merely bounded (and even then, 305/// only ostensibly!), but does not take advantage of any dynamic type info. 306static const CXXRecordDecl *getCXXRecordType(const MemRegion *MR) { 307 if (const auto *TVR = dyn_cast<TypedValueRegion>(MR)) 308 return TVR->getValueType()->getAsCXXRecordDecl(); 309 if (const auto *SR = dyn_cast<SymbolicRegion>(MR)) 310 return SR->getSymbol()->getType()->getPointeeCXXRecordDecl(); 311 return nullptr; 312} 313 314SVal StoreManager::attemptDownCast(SVal Base, QualType TargetType, 315 bool &Failed) { 316 Failed = false; 317 318 const MemRegion *MR = Base.getAsRegion(); 319 if (!MR) 320 return UnknownVal(); 321 322 // Assume the derived class is a pointer or a reference to a CXX record. 323 TargetType = TargetType->getPointeeType(); 324 assert(!TargetType.isNull()); 325 const CXXRecordDecl *TargetClass = TargetType->getAsCXXRecordDecl(); 326 if (!TargetClass && !TargetType->isVoidType()) 327 return UnknownVal(); 328 329 // Drill down the CXXBaseObject chains, which represent upcasts (casts from 330 // derived to base). 331 while (const CXXRecordDecl *MRClass = getCXXRecordType(MR)) { 332 // If found the derived class, the cast succeeds. 333 if (MRClass == TargetClass) 334 return loc::MemRegionVal(MR); 335 336 // We skip over incomplete types. They must be the result of an earlier 337 // reinterpret_cast, as one can only dynamic_cast between types in the same 338 // class hierarchy. 339 if (!TargetType->isVoidType() && MRClass->hasDefinition()) { 340 // Static upcasts are marked as DerivedToBase casts by Sema, so this will 341 // only happen when multiple or virtual inheritance is involved. 342 CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true, 343 /*DetectVirtual=*/false); 344 if (MRClass->isDerivedFrom(TargetClass, Paths)) 345 return evalDerivedToBase(loc::MemRegionVal(MR), Paths.front()); 346 } 347 348 if (const auto *BaseR = dyn_cast<CXXBaseObjectRegion>(MR)) { 349 // Drill down the chain to get the derived classes. 350 MR = BaseR->getSuperRegion(); 351 continue; 352 } 353 354 // If this is a cast to void*, return the region. 355 if (TargetType->isVoidType()) 356 return loc::MemRegionVal(MR); 357 358 // Strange use of reinterpret_cast can give us paths we don't reason 359 // about well, by putting in ElementRegions where we'd expect 360 // CXXBaseObjectRegions. If it's a valid reinterpret_cast (i.e. if the 361 // derived class has a zero offset from the base class), then it's safe 362 // to strip the cast; if it's invalid, -Wreinterpret-base-class should 363 // catch it. In the interest of performance, the analyzer will silently 364 // do the wrong thing in the invalid case (because offsets for subregions 365 // will be wrong). 366 const MemRegion *Uncasted = MR->StripCasts(/*IncludeBaseCasts=*/false); 367 if (Uncasted == MR) { 368 // We reached the bottom of the hierarchy and did not find the derived 369 // class. We must be casting the base to derived, so the cast should 370 // fail. 371 break; 372 } 373 374 MR = Uncasted; 375 } 376 377 // If we're casting a symbolic base pointer to a derived class, use 378 // CXXDerivedObjectRegion to represent the cast. If it's a pointer to an 379 // unrelated type, it must be a weird reinterpret_cast and we have to 380 // be fine with ElementRegion. TODO: Should we instead make 381 // Derived{TargetClass, Element{SourceClass, SR}}? 382 if (const auto *SR = dyn_cast<SymbolicRegion>(MR)) { 383 QualType T = SR->getSymbol()->getType(); 384 const CXXRecordDecl *SourceClass = T->getPointeeCXXRecordDecl(); 385 if (TargetClass && SourceClass && TargetClass->isDerivedFrom(SourceClass)) 386 return loc::MemRegionVal( 387 MRMgr.getCXXDerivedObjectRegion(TargetClass, SR)); 388 return loc::MemRegionVal(GetElementZeroRegion(SR, TargetType)); 389 } 390 391 // We failed if the region we ended up with has perfect type info. 392 Failed = isa<TypedValueRegion>(MR); 393 return UnknownVal(); 394} 395 396static bool hasSameUnqualifiedPointeeType(QualType ty1, QualType ty2) { 397 return ty1->getPointeeType().getCanonicalType().getTypePtr() == 398 ty2->getPointeeType().getCanonicalType().getTypePtr(); 399} 400 401/// CastRetrievedVal - Used by subclasses of StoreManager to implement 402/// implicit casts that arise from loads from regions that are reinterpreted 403/// as another region. 404SVal StoreManager::CastRetrievedVal(SVal V, const TypedValueRegion *R, 405 QualType castTy) { 406 if (castTy.isNull() || V.isUnknownOrUndef()) 407 return V; 408 409 // The dispatchCast() call below would convert the int into a float. 410 // What we want, however, is a bit-by-bit reinterpretation of the int 411 // as a float, which usually yields nothing garbage. For now skip casts 412 // from ints to floats. 413 // TODO: What other combinations of types are affected? 414 if (castTy->isFloatingType()) { 415 SymbolRef Sym = V.getAsSymbol(); 416 if (Sym && !Sym->getType()->isFloatingType()) 417 return UnknownVal(); 418 } 419 420 // When retrieving symbolic pointer and expecting a non-void pointer, 421 // wrap them into element regions of the expected type if necessary. 422 // SValBuilder::dispatchCast() doesn't do that, but it is necessary to 423 // make sure that the retrieved value makes sense, because there's no other 424 // cast in the AST that would tell us to cast it to the correct pointer type. 425 // We might need to do that for non-void pointers as well. 426 // FIXME: We really need a single good function to perform casts for us 427 // correctly every time we need it. 428 if (castTy->isPointerType() && !castTy->isVoidPointerType()) 429 if (const auto *SR = dyn_cast_or_null<SymbolicRegion>(V.getAsRegion())) { 430 QualType sr = SR->getSymbol()->getType(); 431 if (!hasSameUnqualifiedPointeeType(sr, castTy)) 432 return loc::MemRegionVal(castRegion(SR, castTy)); 433 } 434 435 return svalBuilder.dispatchCast(V, castTy); 436} 437 438SVal StoreManager::getLValueFieldOrIvar(const Decl *D, SVal Base) { 439 if (Base.isUnknownOrUndef()) 440 return Base; 441 442 Loc BaseL = Base.castAs<Loc>(); 443 const SubRegion* BaseR = nullptr; 444 445 switch (BaseL.getSubKind()) { 446 case loc::MemRegionValKind: 447 BaseR = cast<SubRegion>(BaseL.castAs<loc::MemRegionVal>().getRegion()); 448 break; 449 450 case loc::GotoLabelKind: 451 // These are anormal cases. Flag an undefined value. 452 return UndefinedVal(); 453 454 case loc::ConcreteIntKind: 455 // While these seem funny, this can happen through casts. 456 // FIXME: What we should return is the field offset, not base. For example, 457 // add the field offset to the integer value. That way things 458 // like this work properly: &(((struct foo *) 0xa)->f) 459 // However, that's not easy to fix without reducing our abilities 460 // to catch null pointer dereference. Eg., ((struct foo *)0x0)->f = 7 461 // is a null dereference even though we're dereferencing offset of f 462 // rather than null. Coming up with an approach that computes offsets 463 // over null pointers properly while still being able to catch null 464 // dereferences might be worth it. 465 return Base; 466 467 default: 468 llvm_unreachable("Unhandled Base."); 469 } 470 471 // NOTE: We must have this check first because ObjCIvarDecl is a subclass 472 // of FieldDecl. 473 if (const auto *ID = dyn_cast<ObjCIvarDecl>(D)) 474 return loc::MemRegionVal(MRMgr.getObjCIvarRegion(ID, BaseR)); 475 476 return loc::MemRegionVal(MRMgr.getFieldRegion(cast<FieldDecl>(D), BaseR)); 477} 478 479SVal StoreManager::getLValueIvar(const ObjCIvarDecl *decl, SVal base) { 480 return getLValueFieldOrIvar(decl, base); 481} 482 483SVal StoreManager::getLValueElement(QualType elementType, NonLoc Offset, 484 SVal Base) { 485 // If the base is an unknown or undefined value, just return it back. 486 // FIXME: For absolute pointer addresses, we just return that value back as 487 // well, although in reality we should return the offset added to that 488 // value. See also the similar FIXME in getLValueFieldOrIvar(). 489 if (Base.isUnknownOrUndef() || Base.getAs<loc::ConcreteInt>()) 490 return Base; 491 492 if (Base.getAs<loc::GotoLabel>()) 493 return UnknownVal(); 494 495 const SubRegion *BaseRegion = 496 Base.castAs<loc::MemRegionVal>().getRegionAs<SubRegion>(); 497 498 // Pointer of any type can be cast and used as array base. 499 const auto *ElemR = dyn_cast<ElementRegion>(BaseRegion); 500 501 // Convert the offset to the appropriate size and signedness. 502 Offset = svalBuilder.convertToArrayIndex(Offset).castAs<NonLoc>(); 503 504 if (!ElemR) { 505 // If the base region is not an ElementRegion, create one. 506 // This can happen in the following example: 507 // 508 // char *p = __builtin_alloc(10); 509 // p[1] = 8; 510 // 511 // Observe that 'p' binds to an AllocaRegion. 512 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, Offset, 513 BaseRegion, Ctx)); 514 } 515 516 SVal BaseIdx = ElemR->getIndex(); 517 518 if (!BaseIdx.getAs<nonloc::ConcreteInt>()) 519 return UnknownVal(); 520 521 const llvm::APSInt &BaseIdxI = 522 BaseIdx.castAs<nonloc::ConcreteInt>().getValue(); 523 524 // Only allow non-integer offsets if the base region has no offset itself. 525 // FIXME: This is a somewhat arbitrary restriction. We should be using 526 // SValBuilder here to add the two offsets without checking their types. 527 if (!Offset.getAs<nonloc::ConcreteInt>()) { 528 if (isa<ElementRegion>(BaseRegion->StripCasts())) 529 return UnknownVal(); 530 531 return loc::MemRegionVal(MRMgr.getElementRegion( 532 elementType, Offset, cast<SubRegion>(ElemR->getSuperRegion()), Ctx)); 533 } 534 535 const llvm::APSInt& OffI = Offset.castAs<nonloc::ConcreteInt>().getValue(); 536 assert(BaseIdxI.isSigned()); 537 538 // Compute the new index. 539 nonloc::ConcreteInt NewIdx(svalBuilder.getBasicValueFactory().getValue(BaseIdxI + 540 OffI)); 541 542 // Construct the new ElementRegion. 543 const SubRegion *ArrayR = cast<SubRegion>(ElemR->getSuperRegion()); 544 return loc::MemRegionVal(MRMgr.getElementRegion(elementType, NewIdx, ArrayR, 545 Ctx)); 546} 547 548StoreManager::BindingsHandler::~BindingsHandler() = default; 549 550bool StoreManager::FindUniqueBinding::HandleBinding(StoreManager& SMgr, 551 Store store, 552 const MemRegion* R, 553 SVal val) { 554 SymbolRef SymV = val.getAsLocSymbol(); 555 if (!SymV || SymV != Sym) 556 return true; 557 558 if (Binding) { 559 First = false; 560 return false; 561 } 562 else 563 Binding = R; 564 565 return true; 566} 567