BugReporterVisitors.cpp revision 5846720f08a6b225484bfe663599c2b057a99bc8
1// BugReporterVisitors.cpp - Helpers for reporting bugs -----------*- 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 a set of BugReporter "visitors" which can be used to 11// enhance the diagnostics reported for a bug. 12// 13//===----------------------------------------------------------------------===// 14#include "clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitor.h" 15#include "clang/AST/Expr.h" 16#include "clang/AST/ExprObjC.h" 17#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h" 18#include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h" 19#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h" 20#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h" 21#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 22#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h" 23#include "llvm/ADT/SmallString.h" 24#include "llvm/ADT/StringExtras.h" 25#include "llvm/Support/raw_ostream.h" 26 27using namespace clang; 28using namespace ento; 29 30//===----------------------------------------------------------------------===// 31// Utility functions. 32//===----------------------------------------------------------------------===// 33 34bool bugreporter::isDeclRefExprToReference(const Expr *E) { 35 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) { 36 return DRE->getDecl()->getType()->isReferenceType(); 37 } 38 return false; 39} 40 41const Expr *bugreporter::getDerefExpr(const Stmt *S) { 42 // Pattern match for a few useful cases (do something smarter later): 43 // a[0], p->f, *p 44 const Expr *E = dyn_cast<Expr>(S); 45 if (!E) 46 return 0; 47 E = E->IgnoreParenCasts(); 48 49 while (true) { 50 if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E)) { 51 assert(B->isAssignmentOp()); 52 E = B->getLHS()->IgnoreParenCasts(); 53 continue; 54 } 55 else if (const UnaryOperator *U = dyn_cast<UnaryOperator>(E)) { 56 if (U->getOpcode() == UO_Deref) 57 return U->getSubExpr()->IgnoreParenCasts(); 58 } 59 else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) { 60 if (ME->isArrow() || isDeclRefExprToReference(ME->getBase())) { 61 return ME->getBase()->IgnoreParenCasts(); 62 } 63 } 64 else if (const ObjCIvarRefExpr *IvarRef = dyn_cast<ObjCIvarRefExpr>(E)) { 65 return IvarRef->getBase()->IgnoreParenCasts(); 66 } 67 else if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(E)) { 68 return AE->getBase(); 69 } 70 break; 71 } 72 73 return NULL; 74} 75 76const Stmt *bugreporter::GetDenomExpr(const ExplodedNode *N) { 77 const Stmt *S = N->getLocationAs<PreStmt>()->getStmt(); 78 if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(S)) 79 return BE->getRHS(); 80 return NULL; 81} 82 83const Stmt *bugreporter::GetRetValExpr(const ExplodedNode *N) { 84 const Stmt *S = N->getLocationAs<PostStmt>()->getStmt(); 85 if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(S)) 86 return RS->getRetValue(); 87 return NULL; 88} 89 90//===----------------------------------------------------------------------===// 91// Definitions for bug reporter visitors. 92//===----------------------------------------------------------------------===// 93 94PathDiagnosticPiece* 95BugReporterVisitor::getEndPath(BugReporterContext &BRC, 96 const ExplodedNode *EndPathNode, 97 BugReport &BR) { 98 return 0; 99} 100 101PathDiagnosticPiece* 102BugReporterVisitor::getDefaultEndPath(BugReporterContext &BRC, 103 const ExplodedNode *EndPathNode, 104 BugReport &BR) { 105 PathDiagnosticLocation L = 106 PathDiagnosticLocation::createEndOfPath(EndPathNode,BRC.getSourceManager()); 107 108 BugReport::ranges_iterator Beg, End; 109 llvm::tie(Beg, End) = BR.getRanges(); 110 111 // Only add the statement itself as a range if we didn't specify any 112 // special ranges for this report. 113 PathDiagnosticPiece *P = new PathDiagnosticEventPiece(L, 114 BR.getDescription(), 115 Beg == End); 116 for (; Beg != End; ++Beg) 117 P->addRange(*Beg); 118 119 return P; 120} 121 122 123namespace { 124/// Emits an extra note at the return statement of an interesting stack frame. 125/// 126/// The returned value is marked as an interesting value, and if it's null, 127/// adds a visitor to track where it became null. 128/// 129/// This visitor is intended to be used when another visitor discovers that an 130/// interesting value comes from an inlined function call. 131class ReturnVisitor : public BugReporterVisitorImpl<ReturnVisitor> { 132 const StackFrameContext *StackFrame; 133 enum { 134 Initial, 135 MaybeSuppress, 136 Satisfied 137 } Mode; 138 139public: 140 ReturnVisitor(const StackFrameContext *Frame) 141 : StackFrame(Frame), Mode(Initial) {} 142 143 static void *getTag() { 144 static int Tag = 0; 145 return static_cast<void *>(&Tag); 146 } 147 148 virtual void Profile(llvm::FoldingSetNodeID &ID) const { 149 ID.AddPointer(ReturnVisitor::getTag()); 150 ID.AddPointer(StackFrame); 151 } 152 153 /// Adds a ReturnVisitor if the given statement represents a call that was 154 /// inlined. 155 /// 156 /// This will search back through the ExplodedGraph, starting from the given 157 /// node, looking for when the given statement was processed. If it turns out 158 /// the statement is a call that was inlined, we add the visitor to the 159 /// bug report, so it can print a note later. 160 static void addVisitorIfNecessary(const ExplodedNode *Node, const Stmt *S, 161 BugReport &BR) { 162 if (!CallEvent::isCallStmt(S)) 163 return; 164 165 // First, find when we processed the statement. 166 do { 167 if (const CallExitEnd *CEE = Node->getLocationAs<CallExitEnd>()) 168 if (CEE->getCalleeContext()->getCallSite() == S) 169 break; 170 if (const StmtPoint *SP = Node->getLocationAs<StmtPoint>()) 171 if (SP->getStmt() == S) 172 break; 173 174 Node = Node->getFirstPred(); 175 } while (Node); 176 177 // Next, step over any post-statement checks. 178 while (Node && isa<PostStmt>(Node->getLocation())) 179 Node = Node->getFirstPred(); 180 181 // Finally, see if we inlined the call. 182 if (Node) { 183 if (const CallExitEnd *CEE = Node->getLocationAs<CallExitEnd>()) { 184 const StackFrameContext *CalleeContext = CEE->getCalleeContext(); 185 if (CalleeContext->getCallSite() == S) { 186 BR.markInteresting(CalleeContext); 187 BR.addVisitor(new ReturnVisitor(CalleeContext)); 188 } 189 } 190 } 191 } 192 193 /// Returns true if any counter-suppression heuristics are enabled for 194 /// ReturnVisitor. 195 static bool hasCounterSuppression(AnalyzerOptions &Options) { 196 return Options.shouldAvoidSuppressingNullArgumentPaths(); 197 } 198 199 PathDiagnosticPiece *visitNodeInitial(const ExplodedNode *N, 200 const ExplodedNode *PrevN, 201 BugReporterContext &BRC, 202 BugReport &BR) { 203 // Only print a message at the interesting return statement. 204 if (N->getLocationContext() != StackFrame) 205 return 0; 206 207 const StmtPoint *SP = N->getLocationAs<StmtPoint>(); 208 if (!SP) 209 return 0; 210 211 const ReturnStmt *Ret = dyn_cast<ReturnStmt>(SP->getStmt()); 212 if (!Ret) 213 return 0; 214 215 // Okay, we're at the right return statement, but do we have the return 216 // value available? 217 ProgramStateRef State = N->getState(); 218 SVal V = State->getSVal(Ret, StackFrame); 219 if (V.isUnknownOrUndef()) 220 return 0; 221 222 // Don't print any more notes after this one. 223 Mode = Satisfied; 224 225 const Expr *RetE = Ret->getRetValue(); 226 assert(RetE && "Tracking a return value for a void function"); 227 RetE = RetE->IgnoreParenCasts(); 228 229 // If we can't prove the return value is 0, just mark it interesting, and 230 // make sure to track it into any further inner functions. 231 if (State->assume(cast<DefinedSVal>(V), true)) { 232 BR.markInteresting(V); 233 ReturnVisitor::addVisitorIfNecessary(N, RetE, BR); 234 return 0; 235 } 236 237 // If we're returning 0, we should track where that 0 came from. 238 bugreporter::trackNullOrUndefValue(N, RetE, BR); 239 240 // Build an appropriate message based on the return value. 241 SmallString<64> Msg; 242 llvm::raw_svector_ostream Out(Msg); 243 244 if (isa<Loc>(V)) { 245 // If we are pruning null-return paths as unlikely error paths, mark the 246 // report invalid. We still want to emit a path note, however, in case 247 // the report is resurrected as valid later on. 248 ExprEngine &Eng = BRC.getBugReporter().getEngine(); 249 AnalyzerOptions &Options = Eng.getAnalysisManager().options; 250 if (Options.shouldSuppressNullReturnPaths()) { 251 if (hasCounterSuppression(Options)) 252 Mode = MaybeSuppress; 253 else 254 BR.markInvalid(ReturnVisitor::getTag(), StackFrame); 255 } 256 257 if (RetE->getType()->isObjCObjectPointerType()) 258 Out << "Returning nil"; 259 else 260 Out << "Returning null pointer"; 261 } else { 262 Out << "Returning zero"; 263 } 264 265 // FIXME: We should have a more generalized location printing mechanism. 266 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(RetE)) 267 if (const DeclaratorDecl *DD = dyn_cast<DeclaratorDecl>(DR->getDecl())) 268 Out << " (loaded from '" << *DD << "')"; 269 270 PathDiagnosticLocation L(Ret, BRC.getSourceManager(), StackFrame); 271 return new PathDiagnosticEventPiece(L, Out.str()); 272 } 273 274 PathDiagnosticPiece *visitNodeMaybeSuppress(const ExplodedNode *N, 275 const ExplodedNode *PrevN, 276 BugReporterContext &BRC, 277 BugReport &BR) { 278 // Are we at the entry node for this call? 279 const CallEnter *CE = N->getLocationAs<CallEnter>(); 280 if (!CE) 281 return 0; 282 283 if (CE->getCalleeContext() != StackFrame) 284 return 0; 285 286 Mode = Satisfied; 287 288 ExprEngine &Eng = BRC.getBugReporter().getEngine(); 289 AnalyzerOptions &Options = Eng.getAnalysisManager().options; 290 if (Options.shouldAvoidSuppressingNullArgumentPaths()) { 291 // Don't automatically suppress a report if one of the arguments is 292 // known to be a null pointer. Instead, start tracking /that/ null 293 // value back to its origin. 294 ProgramStateManager &StateMgr = BRC.getStateManager(); 295 CallEventManager &CallMgr = StateMgr.getCallEventManager(); 296 297 ProgramStateRef State = N->getState(); 298 CallEventRef<> Call = CallMgr.getCaller(StackFrame, State); 299 for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) { 300 SVal ArgV = Call->getArgSVal(I); 301 if (!isa<Loc>(ArgV)) 302 continue; 303 304 const Expr *ArgE = Call->getArgExpr(I); 305 if (!ArgE) 306 continue; 307 308 // Is it possible for this argument to be non-null? 309 if (State->assume(cast<Loc>(ArgV), true)) 310 continue; 311 312 if (bugreporter::trackNullOrUndefValue(N, ArgE, BR, /*IsArg=*/true)) 313 return 0; 314 315 // If we /can't/ track the null pointer, we should err on the side of 316 // false negatives, and continue towards marking this report invalid. 317 // (We will still look at the other arguments, though.) 318 } 319 } 320 321 // There is no reason not to suppress this report; go ahead and do it. 322 BR.markInvalid(ReturnVisitor::getTag(), StackFrame); 323 return 0; 324 } 325 326 PathDiagnosticPiece *VisitNode(const ExplodedNode *N, 327 const ExplodedNode *PrevN, 328 BugReporterContext &BRC, 329 BugReport &BR) { 330 switch (Mode) { 331 case Initial: 332 return visitNodeInitial(N, PrevN, BRC, BR); 333 case MaybeSuppress: 334 return visitNodeMaybeSuppress(N, PrevN, BRC, BR); 335 case Satisfied: 336 return 0; 337 } 338 339 llvm_unreachable("Invalid visit mode!"); 340 } 341}; 342} // end anonymous namespace 343 344 345void FindLastStoreBRVisitor ::Profile(llvm::FoldingSetNodeID &ID) const { 346 static int tag = 0; 347 ID.AddPointer(&tag); 348 ID.AddPointer(R); 349 ID.Add(V); 350} 351 352PathDiagnosticPiece *FindLastStoreBRVisitor::VisitNode(const ExplodedNode *Succ, 353 const ExplodedNode *Pred, 354 BugReporterContext &BRC, 355 BugReport &BR) { 356 357 if (satisfied) 358 return NULL; 359 360 const ExplodedNode *StoreSite = 0; 361 const Expr *InitE = 0; 362 bool IsParam = false; 363 364 // First see if we reached the declaration of the region. 365 if (const VarRegion *VR = dyn_cast<VarRegion>(R)) { 366 if (const PostStmt *P = Pred->getLocationAs<PostStmt>()) { 367 if (const DeclStmt *DS = P->getStmtAs<DeclStmt>()) { 368 if (DS->getSingleDecl() == VR->getDecl()) { 369 StoreSite = Pred; 370 InitE = VR->getDecl()->getInit(); 371 } 372 } 373 } 374 } 375 376 // Otherwise, check that Succ has this binding and Pred does not, i.e. this is 377 // where the binding first occurred. 378 if (!StoreSite) { 379 if (Succ->getState()->getSVal(R) != V) 380 return NULL; 381 if (Pred->getState()->getSVal(R) == V) 382 return NULL; 383 384 StoreSite = Succ; 385 386 // If this is an assignment expression, we can track the value 387 // being assigned. 388 if (const PostStmt *P = Succ->getLocationAs<PostStmt>()) 389 if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>()) 390 if (BO->isAssignmentOp()) 391 InitE = BO->getRHS(); 392 393 // If this is a call entry, the variable should be a parameter. 394 // FIXME: Handle CXXThisRegion as well. (This is not a priority because 395 // 'this' should never be NULL, but this visitor isn't just for NULL and 396 // UndefinedVal.) 397 if (const CallEnter *CE = Succ->getLocationAs<CallEnter>()) { 398 const VarRegion *VR = cast<VarRegion>(R); 399 const ParmVarDecl *Param = cast<ParmVarDecl>(VR->getDecl()); 400 401 ProgramStateManager &StateMgr = BRC.getStateManager(); 402 CallEventManager &CallMgr = StateMgr.getCallEventManager(); 403 404 CallEventRef<> Call = CallMgr.getCaller(CE->getCalleeContext(), 405 Succ->getState()); 406 InitE = Call->getArgExpr(Param->getFunctionScopeIndex()); 407 IsParam = true; 408 } 409 } 410 411 if (!StoreSite) 412 return NULL; 413 satisfied = true; 414 415 // If we have an expression that provided the value, try to track where it 416 // came from. 417 if (InitE) { 418 if (V.isUndef() || isa<loc::ConcreteInt>(V)) { 419 if (!IsParam) 420 InitE = InitE->IgnoreParenCasts(); 421 bugreporter::trackNullOrUndefValue(StoreSite, InitE, BR, IsParam); 422 } else { 423 ReturnVisitor::addVisitorIfNecessary(StoreSite, InitE->IgnoreParenCasts(), 424 BR); 425 } 426 } 427 428 if (!R->canPrintPretty()) 429 return 0; 430 431 // Okay, we've found the binding. Emit an appropriate message. 432 SmallString<256> sbuf; 433 llvm::raw_svector_ostream os(sbuf); 434 435 if (const PostStmt *PS = StoreSite->getLocationAs<PostStmt>()) { 436 const Stmt *S = PS->getStmt(); 437 const char *action = 0; 438 const DeclStmt *DS = dyn_cast<DeclStmt>(S); 439 const VarRegion *VR = dyn_cast<VarRegion>(R); 440 441 if (DS) { 442 action = "initialized to "; 443 } else if (isa<BlockExpr>(S)) { 444 action = "captured by block as "; 445 if (VR) { 446 // See if we can get the BlockVarRegion. 447 ProgramStateRef State = StoreSite->getState(); 448 SVal V = State->getSVal(S, PS->getLocationContext()); 449 if (const BlockDataRegion *BDR = 450 dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) { 451 if (const VarRegion *OriginalR = BDR->getOriginalRegion(VR)) { 452 V = State->getSVal(OriginalR); 453 BR.addVisitor(new FindLastStoreBRVisitor(V, OriginalR)); 454 } 455 } 456 } 457 } 458 459 if (action) { 460 if (!R) 461 return 0; 462 463 os << "Variable '" << *VR->getDecl() << "' "; 464 465 if (isa<loc::ConcreteInt>(V)) { 466 bool b = false; 467 if (R->isBoundable()) { 468 if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) { 469 if (TR->getValueType()->isObjCObjectPointerType()) { 470 os << action << "nil"; 471 b = true; 472 } 473 } 474 } 475 476 if (!b) 477 os << action << "a null pointer value"; 478 } 479 else if (isa<nonloc::ConcreteInt>(V)) { 480 os << action << cast<nonloc::ConcreteInt>(V).getValue(); 481 } 482 else if (DS) { 483 if (V.isUndef()) { 484 if (isa<VarRegion>(R)) { 485 const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl()); 486 if (VD->getInit()) 487 os << "initialized to a garbage value"; 488 else 489 os << "declared without an initial value"; 490 } 491 } 492 else { 493 os << "initialized here"; 494 } 495 } 496 } 497 } else if (isa<CallEnter>(StoreSite->getLocation())) { 498 const ParmVarDecl *Param = cast<ParmVarDecl>(cast<VarRegion>(R)->getDecl()); 499 500 os << "Passing "; 501 502 if (isa<loc::ConcreteInt>(V)) { 503 if (Param->getType()->isObjCObjectPointerType()) 504 os << "nil object reference"; 505 else 506 os << "null pointer value"; 507 } else if (V.isUndef()) { 508 os << "uninitialized value"; 509 } else if (isa<nonloc::ConcreteInt>(V)) { 510 os << "the value " << cast<nonloc::ConcreteInt>(V).getValue(); 511 } else { 512 os << "value"; 513 } 514 515 // Printed parameter indexes are 1-based, not 0-based. 516 unsigned Idx = Param->getFunctionScopeIndex() + 1; 517 os << " via " << Idx << llvm::getOrdinalSuffix(Idx) << " parameter '"; 518 519 R->printPretty(os); 520 os << '\''; 521 } 522 523 if (os.str().empty()) { 524 if (isa<loc::ConcreteInt>(V)) { 525 bool b = false; 526 if (R->isBoundable()) { 527 if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) { 528 if (TR->getValueType()->isObjCObjectPointerType()) { 529 os << "nil object reference stored to "; 530 b = true; 531 } 532 } 533 } 534 535 if (!b) 536 os << "Null pointer value stored to "; 537 } 538 else if (V.isUndef()) { 539 os << "Uninitialized value stored to "; 540 } 541 else if (isa<nonloc::ConcreteInt>(V)) { 542 os << "The value " << cast<nonloc::ConcreteInt>(V).getValue() 543 << " is assigned to "; 544 } 545 else 546 os << "Value assigned to "; 547 548 os << '\''; 549 R->printPretty(os); 550 os << '\''; 551 } 552 553 // Construct a new PathDiagnosticPiece. 554 ProgramPoint P = StoreSite->getLocation(); 555 PathDiagnosticLocation L; 556 if (isa<CallEnter>(P)) 557 L = PathDiagnosticLocation(InitE, BRC.getSourceManager(), 558 P.getLocationContext()); 559 else 560 L = PathDiagnosticLocation::create(P, BRC.getSourceManager()); 561 if (!L.isValid()) 562 return NULL; 563 return new PathDiagnosticEventPiece(L, os.str()); 564} 565 566void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const { 567 static int tag = 0; 568 ID.AddPointer(&tag); 569 ID.AddBoolean(Assumption); 570 ID.Add(Constraint); 571} 572 573/// Return the tag associated with this visitor. This tag will be used 574/// to make all PathDiagnosticPieces created by this visitor. 575const char *TrackConstraintBRVisitor::getTag() { 576 return "TrackConstraintBRVisitor"; 577} 578 579PathDiagnosticPiece * 580TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N, 581 const ExplodedNode *PrevN, 582 BugReporterContext &BRC, 583 BugReport &BR) { 584 if (isSatisfied) 585 return NULL; 586 587 // Check if in the previous state it was feasible for this constraint 588 // to *not* be true. 589 if (PrevN->getState()->assume(Constraint, !Assumption)) { 590 591 isSatisfied = true; 592 593 // As a sanity check, make sure that the negation of the constraint 594 // was infeasible in the current state. If it is feasible, we somehow 595 // missed the transition point. 596 if (N->getState()->assume(Constraint, !Assumption)) 597 return NULL; 598 599 // We found the transition point for the constraint. We now need to 600 // pretty-print the constraint. (work-in-progress) 601 std::string sbuf; 602 llvm::raw_string_ostream os(sbuf); 603 604 if (isa<Loc>(Constraint)) { 605 os << "Assuming pointer value is "; 606 os << (Assumption ? "non-null" : "null"); 607 } 608 609 if (os.str().empty()) 610 return NULL; 611 612 // Construct a new PathDiagnosticPiece. 613 ProgramPoint P = N->getLocation(); 614 PathDiagnosticLocation L = 615 PathDiagnosticLocation::create(P, BRC.getSourceManager()); 616 if (!L.isValid()) 617 return NULL; 618 619 PathDiagnosticEventPiece *X = new PathDiagnosticEventPiece(L, os.str()); 620 X->setTag(getTag()); 621 return X; 622 } 623 624 return NULL; 625} 626 627bool bugreporter::trackNullOrUndefValue(const ExplodedNode *N, const Stmt *S, 628 BugReport &report, bool IsArg) { 629 if (!S || !N) 630 return false; 631 632 if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(S)) 633 S = OVE->getSourceExpr(); 634 635 if (IsArg) { 636 assert(isa<CallEnter>(N->getLocation()) && "Tracking arg but not at call"); 637 } else { 638 // Walk through nodes until we get one that matches the statement exactly. 639 do { 640 const ProgramPoint &pp = N->getLocation(); 641 if (const PostStmt *ps = dyn_cast<PostStmt>(&pp)) { 642 if (ps->getStmt() == S) 643 break; 644 } else if (const CallExitEnd *CEE = dyn_cast<CallExitEnd>(&pp)) { 645 if (CEE->getCalleeContext()->getCallSite() == S) 646 break; 647 } 648 N = N->getFirstPred(); 649 } while (N); 650 651 if (!N) 652 return false; 653 } 654 655 ProgramStateRef state = N->getState(); 656 657 // See if the expression we're interested refers to a variable. 658 // If so, we can track both its contents and constraints on its value. 659 if (const Expr *Ex = dyn_cast<Expr>(S)) { 660 // Strip off parens and casts. Note that this will never have issues with 661 // C++ user-defined implicit conversions, because those have a constructor 662 // or function call inside. 663 Ex = Ex->IgnoreParenCasts(); 664 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex)) { 665 // FIXME: Right now we only track VarDecls because it's non-trivial to 666 // get a MemRegion for any other DeclRefExprs. <rdar://problem/12114812> 667 if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) { 668 ProgramStateManager &StateMgr = state->getStateManager(); 669 MemRegionManager &MRMgr = StateMgr.getRegionManager(); 670 const VarRegion *R = MRMgr.getVarRegion(VD, N->getLocationContext()); 671 672 // Mark both the variable region and its contents as interesting. 673 SVal V = state->getRawSVal(loc::MemRegionVal(R)); 674 675 // If the value matches the default for the variable region, that 676 // might mean that it's been cleared out of the state. Fall back to 677 // the full argument expression (with casts and such intact). 678 if (IsArg) { 679 bool UseArgValue = V.isUnknownOrUndef() || V.isZeroConstant(); 680 if (!UseArgValue) { 681 const SymbolRegionValue *SRV = 682 dyn_cast_or_null<SymbolRegionValue>(V.getAsLocSymbol()); 683 if (SRV) 684 UseArgValue = (SRV->getRegion() == R); 685 } 686 if (UseArgValue) 687 V = state->getSValAsScalarOrLoc(S, N->getLocationContext()); 688 } 689 690 report.markInteresting(R); 691 report.markInteresting(V); 692 report.addVisitor(new UndefOrNullArgVisitor(R)); 693 694 // If the contents are symbolic, find out when they became null. 695 if (V.getAsLocSymbol()) { 696 BugReporterVisitor *ConstraintTracker 697 = new TrackConstraintBRVisitor(cast<DefinedSVal>(V), false); 698 report.addVisitor(ConstraintTracker); 699 } 700 701 report.addVisitor(new FindLastStoreBRVisitor(V, R)); 702 return true; 703 } 704 } 705 } 706 707 // If the expression does NOT refer to a variable, we can still track 708 // constraints on its contents. 709 SVal V = state->getSValAsScalarOrLoc(S, N->getLocationContext()); 710 711 // Uncomment this to find cases where we aren't properly getting the 712 // base value that was dereferenced. 713 // assert(!V.isUnknownOrUndef()); 714 715 // Is it a symbolic value? 716 if (loc::MemRegionVal *L = dyn_cast<loc::MemRegionVal>(&V)) { 717 // At this point we are dealing with the region's LValue. 718 // However, if the rvalue is a symbolic region, we should track it as well. 719 SVal RVal = state->getSVal(L->getRegion()); 720 const MemRegion *RegionRVal = RVal.getAsRegion(); 721 report.addVisitor(new UndefOrNullArgVisitor(L->getRegion())); 722 723 724 if (RegionRVal && isa<SymbolicRegion>(RegionRVal)) { 725 report.markInteresting(RegionRVal); 726 report.addVisitor(new TrackConstraintBRVisitor( 727 loc::MemRegionVal(RegionRVal), false)); 728 } 729 } else { 730 // Otherwise, if the value came from an inlined function call, 731 // we should at least make sure that function isn't pruned in our output. 732 if (const Expr *E = dyn_cast<Expr>(S)) 733 S = E->IgnoreParenCasts(); 734 ReturnVisitor::addVisitorIfNecessary(N, S, report); 735 } 736 737 return true; 738} 739 740BugReporterVisitor * 741FindLastStoreBRVisitor::createVisitorObject(const ExplodedNode *N, 742 const MemRegion *R) { 743 assert(R && "The memory region is null."); 744 745 ProgramStateRef state = N->getState(); 746 SVal V = state->getSVal(R); 747 if (V.isUnknown()) 748 return 0; 749 750 return new FindLastStoreBRVisitor(V, R); 751} 752 753 754PathDiagnosticPiece *NilReceiverBRVisitor::VisitNode(const ExplodedNode *N, 755 const ExplodedNode *PrevN, 756 BugReporterContext &BRC, 757 BugReport &BR) { 758 const PostStmt *P = N->getLocationAs<PostStmt>(); 759 if (!P) 760 return 0; 761 const ObjCMessageExpr *ME = P->getStmtAs<ObjCMessageExpr>(); 762 if (!ME) 763 return 0; 764 const Expr *Receiver = ME->getInstanceReceiver(); 765 if (!Receiver) 766 return 0; 767 ProgramStateRef state = N->getState(); 768 const SVal &V = state->getSVal(Receiver, N->getLocationContext()); 769 const DefinedOrUnknownSVal *DV = dyn_cast<DefinedOrUnknownSVal>(&V); 770 if (!DV) 771 return 0; 772 state = state->assume(*DV, true); 773 if (state) 774 return 0; 775 776 // The receiver was nil, and hence the method was skipped. 777 // Register a BugReporterVisitor to issue a message telling us how 778 // the receiver was null. 779 bugreporter::trackNullOrUndefValue(N, Receiver, BR); 780 // Issue a message saying that the method was skipped. 781 PathDiagnosticLocation L(Receiver, BRC.getSourceManager(), 782 N->getLocationContext()); 783 return new PathDiagnosticEventPiece(L, "No method is called " 784 "because the receiver is nil"); 785} 786 787// Registers every VarDecl inside a Stmt with a last store visitor. 788void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR, 789 const Stmt *S) { 790 const ExplodedNode *N = BR.getErrorNode(); 791 std::deque<const Stmt *> WorkList; 792 WorkList.push_back(S); 793 794 while (!WorkList.empty()) { 795 const Stmt *Head = WorkList.front(); 796 WorkList.pop_front(); 797 798 ProgramStateRef state = N->getState(); 799 ProgramStateManager &StateMgr = state->getStateManager(); 800 801 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Head)) { 802 if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) { 803 const VarRegion *R = 804 StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext()); 805 806 // What did we load? 807 SVal V = state->getSVal(S, N->getLocationContext()); 808 809 if (isa<loc::ConcreteInt>(V) || isa<nonloc::ConcreteInt>(V)) { 810 // Register a new visitor with the BugReport. 811 BR.addVisitor(new FindLastStoreBRVisitor(V, R)); 812 } 813 } 814 } 815 816 for (Stmt::const_child_iterator I = Head->child_begin(); 817 I != Head->child_end(); ++I) 818 WorkList.push_back(*I); 819 } 820} 821 822//===----------------------------------------------------------------------===// 823// Visitor that tries to report interesting diagnostics from conditions. 824//===----------------------------------------------------------------------===// 825 826/// Return the tag associated with this visitor. This tag will be used 827/// to make all PathDiagnosticPieces created by this visitor. 828const char *ConditionBRVisitor::getTag() { 829 return "ConditionBRVisitor"; 830} 831 832PathDiagnosticPiece *ConditionBRVisitor::VisitNode(const ExplodedNode *N, 833 const ExplodedNode *Prev, 834 BugReporterContext &BRC, 835 BugReport &BR) { 836 PathDiagnosticPiece *piece = VisitNodeImpl(N, Prev, BRC, BR); 837 if (piece) { 838 piece->setTag(getTag()); 839 if (PathDiagnosticEventPiece *ev=dyn_cast<PathDiagnosticEventPiece>(piece)) 840 ev->setPrunable(true, /* override */ false); 841 } 842 return piece; 843} 844 845PathDiagnosticPiece *ConditionBRVisitor::VisitNodeImpl(const ExplodedNode *N, 846 const ExplodedNode *Prev, 847 BugReporterContext &BRC, 848 BugReport &BR) { 849 850 ProgramPoint progPoint = N->getLocation(); 851 ProgramStateRef CurrentState = N->getState(); 852 ProgramStateRef PrevState = Prev->getState(); 853 854 // Compare the GDMs of the state, because that is where constraints 855 // are managed. Note that ensure that we only look at nodes that 856 // were generated by the analyzer engine proper, not checkers. 857 if (CurrentState->getGDM().getRoot() == 858 PrevState->getGDM().getRoot()) 859 return 0; 860 861 // If an assumption was made on a branch, it should be caught 862 // here by looking at the state transition. 863 if (const BlockEdge *BE = dyn_cast<BlockEdge>(&progPoint)) { 864 const CFGBlock *srcBlk = BE->getSrc(); 865 if (const Stmt *term = srcBlk->getTerminator()) 866 return VisitTerminator(term, N, srcBlk, BE->getDst(), BR, BRC); 867 return 0; 868 } 869 870 if (const PostStmt *PS = dyn_cast<PostStmt>(&progPoint)) { 871 // FIXME: Assuming that BugReporter is a GRBugReporter is a layering 872 // violation. 873 const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags = 874 cast<GRBugReporter>(BRC.getBugReporter()). 875 getEngine().geteagerlyAssumeBinOpBifurcationTags(); 876 877 const ProgramPointTag *tag = PS->getTag(); 878 if (tag == tags.first) 879 return VisitTrueTest(cast<Expr>(PS->getStmt()), true, 880 BRC, BR, N); 881 if (tag == tags.second) 882 return VisitTrueTest(cast<Expr>(PS->getStmt()), false, 883 BRC, BR, N); 884 885 return 0; 886 } 887 888 return 0; 889} 890 891PathDiagnosticPiece * 892ConditionBRVisitor::VisitTerminator(const Stmt *Term, 893 const ExplodedNode *N, 894 const CFGBlock *srcBlk, 895 const CFGBlock *dstBlk, 896 BugReport &R, 897 BugReporterContext &BRC) { 898 const Expr *Cond = 0; 899 900 switch (Term->getStmtClass()) { 901 default: 902 return 0; 903 case Stmt::IfStmtClass: 904 Cond = cast<IfStmt>(Term)->getCond(); 905 break; 906 case Stmt::ConditionalOperatorClass: 907 Cond = cast<ConditionalOperator>(Term)->getCond(); 908 break; 909 } 910 911 assert(Cond); 912 assert(srcBlk->succ_size() == 2); 913 const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk; 914 return VisitTrueTest(Cond, tookTrue, BRC, R, N); 915} 916 917PathDiagnosticPiece * 918ConditionBRVisitor::VisitTrueTest(const Expr *Cond, 919 bool tookTrue, 920 BugReporterContext &BRC, 921 BugReport &R, 922 const ExplodedNode *N) { 923 924 const Expr *Ex = Cond; 925 926 while (true) { 927 Ex = Ex->IgnoreParenCasts(); 928 switch (Ex->getStmtClass()) { 929 default: 930 return 0; 931 case Stmt::BinaryOperatorClass: 932 return VisitTrueTest(Cond, cast<BinaryOperator>(Ex), tookTrue, BRC, 933 R, N); 934 case Stmt::DeclRefExprClass: 935 return VisitTrueTest(Cond, cast<DeclRefExpr>(Ex), tookTrue, BRC, 936 R, N); 937 case Stmt::UnaryOperatorClass: { 938 const UnaryOperator *UO = cast<UnaryOperator>(Ex); 939 if (UO->getOpcode() == UO_LNot) { 940 tookTrue = !tookTrue; 941 Ex = UO->getSubExpr(); 942 continue; 943 } 944 return 0; 945 } 946 } 947 } 948} 949 950bool ConditionBRVisitor::patternMatch(const Expr *Ex, raw_ostream &Out, 951 BugReporterContext &BRC, 952 BugReport &report, 953 const ExplodedNode *N, 954 llvm::Optional<bool> &prunable) { 955 const Expr *OriginalExpr = Ex; 956 Ex = Ex->IgnoreParenCasts(); 957 958 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex)) { 959 const bool quotes = isa<VarDecl>(DR->getDecl()); 960 if (quotes) { 961 Out << '\''; 962 const LocationContext *LCtx = N->getLocationContext(); 963 const ProgramState *state = N->getState().getPtr(); 964 if (const MemRegion *R = state->getLValue(cast<VarDecl>(DR->getDecl()), 965 LCtx).getAsRegion()) { 966 if (report.isInteresting(R)) 967 prunable = false; 968 else { 969 const ProgramState *state = N->getState().getPtr(); 970 SVal V = state->getSVal(R); 971 if (report.isInteresting(V)) 972 prunable = false; 973 } 974 } 975 } 976 Out << DR->getDecl()->getDeclName().getAsString(); 977 if (quotes) 978 Out << '\''; 979 return quotes; 980 } 981 982 if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(Ex)) { 983 QualType OriginalTy = OriginalExpr->getType(); 984 if (OriginalTy->isPointerType()) { 985 if (IL->getValue() == 0) { 986 Out << "null"; 987 return false; 988 } 989 } 990 else if (OriginalTy->isObjCObjectPointerType()) { 991 if (IL->getValue() == 0) { 992 Out << "nil"; 993 return false; 994 } 995 } 996 997 Out << IL->getValue(); 998 return false; 999 } 1000 1001 return false; 1002} 1003 1004PathDiagnosticPiece * 1005ConditionBRVisitor::VisitTrueTest(const Expr *Cond, 1006 const BinaryOperator *BExpr, 1007 const bool tookTrue, 1008 BugReporterContext &BRC, 1009 BugReport &R, 1010 const ExplodedNode *N) { 1011 1012 bool shouldInvert = false; 1013 llvm::Optional<bool> shouldPrune; 1014 1015 SmallString<128> LhsString, RhsString; 1016 { 1017 llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString); 1018 const bool isVarLHS = patternMatch(BExpr->getLHS(), OutLHS, BRC, R, N, 1019 shouldPrune); 1020 const bool isVarRHS = patternMatch(BExpr->getRHS(), OutRHS, BRC, R, N, 1021 shouldPrune); 1022 1023 shouldInvert = !isVarLHS && isVarRHS; 1024 } 1025 1026 BinaryOperator::Opcode Op = BExpr->getOpcode(); 1027 1028 if (BinaryOperator::isAssignmentOp(Op)) { 1029 // For assignment operators, all that we care about is that the LHS 1030 // evaluates to "true" or "false". 1031 return VisitConditionVariable(LhsString, BExpr->getLHS(), tookTrue, 1032 BRC, R, N); 1033 } 1034 1035 // For non-assignment operations, we require that we can understand 1036 // both the LHS and RHS. 1037 if (LhsString.empty() || RhsString.empty()) 1038 return 0; 1039 1040 // Should we invert the strings if the LHS is not a variable name? 1041 SmallString<256> buf; 1042 llvm::raw_svector_ostream Out(buf); 1043 Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is "; 1044 1045 // Do we need to invert the opcode? 1046 if (shouldInvert) 1047 switch (Op) { 1048 default: break; 1049 case BO_LT: Op = BO_GT; break; 1050 case BO_GT: Op = BO_LT; break; 1051 case BO_LE: Op = BO_GE; break; 1052 case BO_GE: Op = BO_LE; break; 1053 } 1054 1055 if (!tookTrue) 1056 switch (Op) { 1057 case BO_EQ: Op = BO_NE; break; 1058 case BO_NE: Op = BO_EQ; break; 1059 case BO_LT: Op = BO_GE; break; 1060 case BO_GT: Op = BO_LE; break; 1061 case BO_LE: Op = BO_GT; break; 1062 case BO_GE: Op = BO_LT; break; 1063 default: 1064 return 0; 1065 } 1066 1067 switch (Op) { 1068 case BO_EQ: 1069 Out << "equal to "; 1070 break; 1071 case BO_NE: 1072 Out << "not equal to "; 1073 break; 1074 default: 1075 Out << BinaryOperator::getOpcodeStr(Op) << ' '; 1076 break; 1077 } 1078 1079 Out << (shouldInvert ? LhsString : RhsString); 1080 const LocationContext *LCtx = N->getLocationContext(); 1081 PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx); 1082 PathDiagnosticEventPiece *event = 1083 new PathDiagnosticEventPiece(Loc, Out.str()); 1084 if (shouldPrune.hasValue()) 1085 event->setPrunable(shouldPrune.getValue()); 1086 return event; 1087} 1088 1089PathDiagnosticPiece * 1090ConditionBRVisitor::VisitConditionVariable(StringRef LhsString, 1091 const Expr *CondVarExpr, 1092 const bool tookTrue, 1093 BugReporterContext &BRC, 1094 BugReport &report, 1095 const ExplodedNode *N) { 1096 // FIXME: If there's already a constraint tracker for this variable, 1097 // we shouldn't emit anything here (c.f. the double note in 1098 // test/Analysis/inlining/path-notes.c) 1099 SmallString<256> buf; 1100 llvm::raw_svector_ostream Out(buf); 1101 Out << "Assuming " << LhsString << " is "; 1102 1103 QualType Ty = CondVarExpr->getType(); 1104 1105 if (Ty->isPointerType()) 1106 Out << (tookTrue ? "not null" : "null"); 1107 else if (Ty->isObjCObjectPointerType()) 1108 Out << (tookTrue ? "not nil" : "nil"); 1109 else if (Ty->isBooleanType()) 1110 Out << (tookTrue ? "true" : "false"); 1111 else if (Ty->isIntegerType()) 1112 Out << (tookTrue ? "non-zero" : "zero"); 1113 else 1114 return 0; 1115 1116 const LocationContext *LCtx = N->getLocationContext(); 1117 PathDiagnosticLocation Loc(CondVarExpr, BRC.getSourceManager(), LCtx); 1118 PathDiagnosticEventPiece *event = 1119 new PathDiagnosticEventPiece(Loc, Out.str()); 1120 1121 if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(CondVarExpr)) { 1122 if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) { 1123 const ProgramState *state = N->getState().getPtr(); 1124 if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) { 1125 if (report.isInteresting(R)) 1126 event->setPrunable(false); 1127 } 1128 } 1129 } 1130 1131 return event; 1132} 1133 1134PathDiagnosticPiece * 1135ConditionBRVisitor::VisitTrueTest(const Expr *Cond, 1136 const DeclRefExpr *DR, 1137 const bool tookTrue, 1138 BugReporterContext &BRC, 1139 BugReport &report, 1140 const ExplodedNode *N) { 1141 1142 const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl()); 1143 if (!VD) 1144 return 0; 1145 1146 SmallString<256> Buf; 1147 llvm::raw_svector_ostream Out(Buf); 1148 1149 Out << "Assuming '"; 1150 VD->getDeclName().printName(Out); 1151 Out << "' is "; 1152 1153 QualType VDTy = VD->getType(); 1154 1155 if (VDTy->isPointerType()) 1156 Out << (tookTrue ? "non-null" : "null"); 1157 else if (VDTy->isObjCObjectPointerType()) 1158 Out << (tookTrue ? "non-nil" : "nil"); 1159 else if (VDTy->isScalarType()) 1160 Out << (tookTrue ? "not equal to 0" : "0"); 1161 else 1162 return 0; 1163 1164 const LocationContext *LCtx = N->getLocationContext(); 1165 PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx); 1166 PathDiagnosticEventPiece *event = 1167 new PathDiagnosticEventPiece(Loc, Out.str()); 1168 1169 const ProgramState *state = N->getState().getPtr(); 1170 if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) { 1171 if (report.isInteresting(R)) 1172 event->setPrunable(false); 1173 else { 1174 SVal V = state->getSVal(R); 1175 if (report.isInteresting(V)) 1176 event->setPrunable(false); 1177 } 1178 } 1179 return event; 1180} 1181 1182PathDiagnosticPiece * 1183LikelyFalsePositiveSuppressionBRVisitor::getEndPath(BugReporterContext &BRC, 1184 const ExplodedNode *N, 1185 BugReport &BR) { 1186 const Stmt *S = BR.getStmt(); 1187 if (!S) 1188 return 0; 1189 1190 // Here we suppress false positives coming from system macros. This list is 1191 // based on known issues. 1192 1193 // Skip reports within the sys/queue.h macros as we do not have the ability to 1194 // reason about data structure shapes. 1195 SourceManager &SM = BRC.getSourceManager(); 1196 SourceLocation Loc = S->getLocStart(); 1197 while (Loc.isMacroID()) { 1198 if (SM.isInSystemMacro(Loc) && 1199 (SM.getFilename(SM.getSpellingLoc(Loc)).endswith("sys/queue.h"))) { 1200 BR.markInvalid(getTag(), 0); 1201 return 0; 1202 } 1203 Loc = SM.getSpellingLoc(Loc); 1204 } 1205 1206 return 0; 1207} 1208 1209PathDiagnosticPiece * 1210UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N, 1211 const ExplodedNode *PrevN, 1212 BugReporterContext &BRC, 1213 BugReport &BR) { 1214 1215 ProgramStateRef State = N->getState(); 1216 ProgramPoint ProgLoc = N->getLocation(); 1217 1218 // We are only interested in visiting CallEnter nodes. 1219 CallEnter *CEnter = dyn_cast<CallEnter>(&ProgLoc); 1220 if (!CEnter) 1221 return 0; 1222 1223 // Check if one of the arguments is the region the visitor is tracking. 1224 CallEventManager &CEMgr = BRC.getStateManager().getCallEventManager(); 1225 CallEventRef<> Call = CEMgr.getCaller(CEnter->getCalleeContext(), State); 1226 unsigned Idx = 0; 1227 for (CallEvent::param_iterator I = Call->param_begin(), 1228 E = Call->param_end(); I != E; ++I, ++Idx) { 1229 const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion(); 1230 1231 // Are we tracking the argument or its subregion? 1232 if ( !ArgReg || (ArgReg != R && !R->isSubRegionOf(ArgReg->StripCasts()))) 1233 continue; 1234 1235 // Check the function parameter type. 1236 const ParmVarDecl *ParamDecl = *I; 1237 assert(ParamDecl && "Formal parameter has no decl?"); 1238 QualType T = ParamDecl->getType(); 1239 1240 if (!(T->isAnyPointerType() || T->isReferenceType())) { 1241 // Function can only change the value passed in by address. 1242 continue; 1243 } 1244 1245 // If it is a const pointer value, the function does not intend to 1246 // change the value. 1247 if (T->getPointeeType().isConstQualified()) 1248 continue; 1249 1250 // Mark the call site (LocationContext) as interesting if the value of the 1251 // argument is undefined or '0'/'NULL'. 1252 SVal BoundVal = State->getSVal(R); 1253 if (BoundVal.isUndef() || BoundVal.isZeroConstant()) { 1254 BR.markInteresting(CEnter->getCalleeContext()); 1255 return 0; 1256 } 1257 } 1258 return 0; 1259} 1260