ExprEngineCallAndReturn.cpp revision e460c46c5d602f65354cab0879c458890273591c
1//=-- ExprEngineCallAndReturn.cpp - Support for call/return -----*- 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 calls and returns. 11// 12//===----------------------------------------------------------------------===// 13 14#include "clang/Analysis/Analyses/LiveVariables.h" 15#include "clang/StaticAnalyzer/Core/CheckerManager.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 17#include "clang/StaticAnalyzer/Core/PathSensitive/Calls.h" 18#include "clang/AST/DeclCXX.h" 19#include "llvm/ADT/SmallSet.h" 20#include "llvm/Support/SaveAndRestore.h" 21 22using namespace clang; 23using namespace ento; 24 25static CallEventKind classifyCallExpr(const CallExpr *CE) { 26 if (isa<CXXMemberCallExpr>(CE)) 27 return CE_CXXMember; 28 29 const CXXOperatorCallExpr *OpCE = dyn_cast<CXXOperatorCallExpr>(CE); 30 if (OpCE) { 31 const FunctionDecl *DirectCallee = CE->getDirectCallee(); 32 if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(DirectCallee)) 33 if (MD->isInstance()) 34 return CE_CXXMemberOperator; 35 } else if (CE->getCallee()->getType()->isBlockPointerType()) { 36 return CE_Block; 37 } 38 39 return CE_Function; 40} 41 42void ExprEngine::processCallEnter(CallEnter CE, ExplodedNode *Pred) { 43 // Get the entry block in the CFG of the callee. 44 const StackFrameContext *calleeCtx = CE.getCalleeContext(); 45 const CFG *CalleeCFG = calleeCtx->getCFG(); 46 const CFGBlock *Entry = &(CalleeCFG->getEntry()); 47 48 // Validate the CFG. 49 assert(Entry->empty()); 50 assert(Entry->succ_size() == 1); 51 52 // Get the solitary sucessor. 53 const CFGBlock *Succ = *(Entry->succ_begin()); 54 55 // Construct an edge representing the starting location in the callee. 56 BlockEdge Loc(Entry, Succ, calleeCtx); 57 58 ProgramStateRef state = Pred->getState(); 59 60 // Construct a new node and add it to the worklist. 61 bool isNew; 62 ExplodedNode *Node = G.getNode(Loc, state, false, &isNew); 63 Node->addPredecessor(Pred, G); 64 if (isNew) 65 Engine.getWorkList()->enqueue(Node); 66} 67 68// Find the last statement on the path to the exploded node and the 69// corresponding Block. 70static std::pair<const Stmt*, 71 const CFGBlock*> getLastStmt(const ExplodedNode *Node) { 72 const Stmt *S = 0; 73 const StackFrameContext *SF = 74 Node->getLocation().getLocationContext()->getCurrentStackFrame(); 75 76 // Back up through the ExplodedGraph until we reach a statement node. 77 while (Node) { 78 const ProgramPoint &PP = Node->getLocation(); 79 80 if (const StmtPoint *SP = dyn_cast<StmtPoint>(&PP)) { 81 S = SP->getStmt(); 82 break; 83 } else if (const CallExitEnd *CEE = dyn_cast<CallExitEnd>(&PP)) { 84 S = CEE->getCalleeContext()->getCallSite(); 85 if (S) 86 break; 87 // If we have an implicit call, we'll probably end up with a 88 // StmtPoint inside the callee, which is acceptable. 89 // (It's possible a function ONLY contains implicit calls -- such as an 90 // implicitly-generated destructor -- so we shouldn't just skip back to 91 // the CallEnter node and keep going.) 92 } else if (const CallEnter *CE = dyn_cast<CallEnter>(&PP)) { 93 // If we reached the CallEnter for this function, it has no statements. 94 if (CE->getCalleeContext() == SF) 95 break; 96 } 97 98 Node = *Node->pred_begin(); 99 } 100 101 const CFGBlock *Blk = 0; 102 if (S) { 103 // Now, get the enclosing basic block. 104 while (Node && Node->pred_size() >=1 ) { 105 const ProgramPoint &PP = Node->getLocation(); 106 if (isa<BlockEdge>(PP) && 107 (PP.getLocationContext()->getCurrentStackFrame() == SF)) { 108 BlockEdge &EPP = cast<BlockEdge>(PP); 109 Blk = EPP.getDst(); 110 break; 111 } 112 Node = *Node->pred_begin(); 113 } 114 } 115 116 return std::pair<const Stmt*, const CFGBlock*>(S, Blk); 117} 118 119/// The call exit is simulated with a sequence of nodes, which occur between 120/// CallExitBegin and CallExitEnd. The following operations occur between the 121/// two program points: 122/// 1. CallExitBegin (triggers the start of call exit sequence) 123/// 2. Bind the return value 124/// 3. Run Remove dead bindings to clean up the dead symbols from the callee. 125/// 4. CallExitEnd (switch to the caller context) 126/// 5. PostStmt<CallExpr> 127void ExprEngine::processCallExit(ExplodedNode *CEBNode) { 128 // Step 1 CEBNode was generated before the call. 129 130 const StackFrameContext *calleeCtx = 131 CEBNode->getLocationContext()->getCurrentStackFrame(); 132 133 // The parent context might not be a stack frame, so make sure we 134 // look up the first enclosing stack frame. 135 const StackFrameContext *callerCtx = 136 calleeCtx->getParent()->getCurrentStackFrame(); 137 138 const Stmt *CE = calleeCtx->getCallSite(); 139 ProgramStateRef state = CEBNode->getState(); 140 // Find the last statement in the function and the corresponding basic block. 141 const Stmt *LastSt = 0; 142 const CFGBlock *Blk = 0; 143 llvm::tie(LastSt, Blk) = getLastStmt(CEBNode); 144 145 // Step 2: generate node with bound return value: CEBNode -> BindedRetNode. 146 147 // If the callee returns an expression, bind its value to CallExpr. 148 if (CE) { 149 if (const ReturnStmt *RS = dyn_cast_or_null<ReturnStmt>(LastSt)) { 150 const LocationContext *LCtx = CEBNode->getLocationContext(); 151 SVal V = state->getSVal(RS, LCtx); 152 state = state->BindExpr(CE, calleeCtx->getParent(), V); 153 } 154 155 // Bind the constructed object value to CXXConstructExpr. 156 if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(CE)) { 157 loc::MemRegionVal This = 158 svalBuilder.getCXXThis(CCE->getConstructor()->getParent(), calleeCtx); 159 SVal ThisV = state->getSVal(This); 160 161 // Always bind the region to the CXXConstructExpr. 162 state = state->BindExpr(CCE, calleeCtx->getParent(), ThisV); 163 } 164 } 165 166 // Step 3: BindedRetNode -> CleanedNodes 167 // If we can find a statement and a block in the inlined function, run remove 168 // dead bindings before returning from the call. This is important to ensure 169 // that we report the issues such as leaks in the stack contexts in which 170 // they occurred. 171 ExplodedNodeSet CleanedNodes; 172 if (LastSt && Blk) { 173 static SimpleProgramPointTag retValBind("ExprEngine : Bind Return Value"); 174 PostStmt Loc(LastSt, calleeCtx, &retValBind); 175 bool isNew; 176 ExplodedNode *BindedRetNode = G.getNode(Loc, state, false, &isNew); 177 BindedRetNode->addPredecessor(CEBNode, G); 178 if (!isNew) 179 return; 180 181 NodeBuilderContext Ctx(getCoreEngine(), Blk, BindedRetNode); 182 currentBuilderContext = &Ctx; 183 // Here, we call the Symbol Reaper with 0 statement and caller location 184 // context, telling it to clean up everything in the callee's context 185 // (and it's children). We use LastStmt as a diagnostic statement, which 186 // which the PreStmtPurge Dead point will be associated. 187 removeDead(BindedRetNode, CleanedNodes, 0, callerCtx, LastSt, 188 ProgramPoint::PostStmtPurgeDeadSymbolsKind); 189 currentBuilderContext = 0; 190 } else { 191 CleanedNodes.Add(CEBNode); 192 } 193 194 for (ExplodedNodeSet::iterator I = CleanedNodes.begin(), 195 E = CleanedNodes.end(); I != E; ++I) { 196 197 // Step 4: Generate the CallExit and leave the callee's context. 198 // CleanedNodes -> CEENode 199 CallExitEnd Loc(calleeCtx, callerCtx); 200 bool isNew; 201 ProgramStateRef CEEState = (*I == CEBNode) ? state : (*I)->getState(); 202 ExplodedNode *CEENode = G.getNode(Loc, CEEState, false, &isNew); 203 CEENode->addPredecessor(*I, G); 204 if (!isNew) 205 return; 206 207 // Step 5: Perform the post-condition check of the CallExpr and enqueue the 208 // result onto the work list. 209 // CEENode -> Dst -> WorkList 210 ExplodedNodeSet Dst; 211 NodeBuilderContext Ctx(Engine, calleeCtx->getCallSiteBlock(), CEENode); 212 SaveAndRestore<const NodeBuilderContext*> NBCSave(currentBuilderContext, 213 &Ctx); 214 SaveAndRestore<unsigned> CBISave(currentStmtIdx, calleeCtx->getIndex()); 215 216 // FIXME: This needs to call PostCall. 217 // FIXME: If/when we inline Objective-C messages, this also needs to call 218 // PostObjCMessage. 219 if (CE) 220 getCheckerManager().runCheckersForPostStmt(Dst, CEENode, CE, *this, true); 221 else 222 Dst.Add(CEENode); 223 224 // Enqueue the next element in the block. 225 for (ExplodedNodeSet::iterator PSI = Dst.begin(), PSE = Dst.end(); 226 PSI != PSE; ++PSI) { 227 Engine.getWorkList()->enqueue(*PSI, calleeCtx->getCallSiteBlock(), 228 calleeCtx->getIndex()+1); 229 } 230 } 231} 232 233static unsigned getNumberStackFrames(const LocationContext *LCtx) { 234 unsigned count = 0; 235 while (LCtx) { 236 if (isa<StackFrameContext>(LCtx)) 237 ++count; 238 LCtx = LCtx->getParent(); 239 } 240 return count; 241} 242 243// Determine if we should inline the call. 244bool ExprEngine::shouldInlineDecl(const Decl *D, ExplodedNode *Pred) { 245 AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(D); 246 const CFG *CalleeCFG = CalleeADC->getCFG(); 247 248 // It is possible that the CFG cannot be constructed. 249 // Be safe, and check if the CalleeCFG is valid. 250 if (!CalleeCFG) 251 return false; 252 253 if (getNumberStackFrames(Pred->getLocationContext()) 254 == AMgr.InlineMaxStackDepth) 255 return false; 256 257 if (Engine.FunctionSummaries->hasReachedMaxBlockCount(D)) 258 return false; 259 260 if (CalleeCFG->getNumBlockIDs() > AMgr.InlineMaxFunctionSize) 261 return false; 262 263 // Do not inline variadic calls (for now). 264 if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) { 265 if (BD->isVariadic()) 266 return false; 267 } 268 else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) { 269 if (FD->isVariadic()) 270 return false; 271 } 272 273 // It is possible that the live variables analysis cannot be 274 // run. If so, bail out. 275 if (!CalleeADC->getAnalysis<RelaxedLiveVariables>()) 276 return false; 277 278 return true; 279} 280 281bool ExprEngine::inlineCall(const CallEvent &Call, 282 ExplodedNode *Pred) { 283 if (!getAnalysisManager().shouldInlineCall()) 284 return false; 285 286 const Decl *D = Call.getRuntimeDefinition(); 287 if (!D) 288 return false; 289 290 const LocationContext *CurLC = Pred->getLocationContext(); 291 const StackFrameContext *CallerSFC = CurLC->getCurrentStackFrame(); 292 const LocationContext *ParentOfCallee = 0; 293 294 switch (Call.getKind()) { 295 case CE_Function: 296 case CE_CXXMember: 297 case CE_CXXMemberOperator: 298 // These are always at least possible to inline. 299 break; 300 case CE_CXXConstructor: 301 case CE_CXXDestructor: { 302 // Only inline constructors and destructors if we built the CFGs for them 303 // properly. 304 const AnalysisDeclContext *ADC = CallerSFC->getAnalysisDeclContext(); 305 if (!ADC->getCFGBuildOptions().AddImplicitDtors || 306 !ADC->getCFGBuildOptions().AddInitializers) 307 return false; 308 309 // FIXME: We don't handle constructors or destructors for arrays properly. 310 const MemRegion *Target = Call.getCXXThisVal().getAsRegion(); 311 if (Target && isa<ElementRegion>(Target)) 312 return false; 313 314 // FIXME: This is a hack. We don't handle temporary destructors 315 // right now, so we shouldn't inline their constructors. 316 if (const CXXConstructorCall *Ctor = dyn_cast<CXXConstructorCall>(&Call)) { 317 const CXXConstructExpr *CtorExpr = Ctor->getOriginExpr(); 318 if (CtorExpr->getConstructionKind() == CXXConstructExpr::CK_Complete) 319 if (!Target || !isa<DeclRegion>(Target)) 320 return false; 321 } 322 break; 323 } 324 case CE_CXXAllocator: 325 // Do not inline allocators until we model deallocators. 326 // This is unfortunate, but basically necessary for smart pointers and such. 327 return false; 328 case CE_Block: { 329 const BlockDataRegion *BR = cast<BlockCall>(Call).getBlockRegion(); 330 assert(BR && "If we have the block definition we should have its region"); 331 AnalysisDeclContext *BlockCtx = AMgr.getAnalysisDeclContext(D); 332 ParentOfCallee = BlockCtx->getBlockInvocationContext(CallerSFC, 333 cast<BlockDecl>(D), 334 BR); 335 break; 336 } 337 case CE_ObjCMessage: 338 break; 339 } 340 341 if (!shouldInlineDecl(D, Pred)) 342 return false; 343 344 if (!ParentOfCallee) 345 ParentOfCallee = CallerSFC; 346 347 // This may be NULL, but that's fine. 348 const Expr *CallE = Call.getOriginExpr(); 349 350 // Construct a new stack frame for the callee. 351 AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(D); 352 const StackFrameContext *CalleeSFC = 353 CalleeADC->getStackFrame(ParentOfCallee, CallE, 354 currentBuilderContext->getBlock(), 355 currentStmtIdx); 356 357 CallEnter Loc(CallE, CalleeSFC, CurLC); 358 359 // Construct a new state which contains the mapping from actual to 360 // formal arguments. 361 ProgramStateRef State = Pred->getState()->enterStackFrame(Call, CalleeSFC); 362 363 bool isNew; 364 if (ExplodedNode *N = G.getNode(Loc, State, false, &isNew)) { 365 N->addPredecessor(Pred, G); 366 if (isNew) 367 Engine.getWorkList()->enqueue(N); 368 } 369 return true; 370} 371 372static ProgramStateRef getInlineFailedState(ProgramStateRef State, 373 const Stmt *CallE) { 374 void *ReplayState = State->get<ReplayWithoutInlining>(); 375 if (!ReplayState) 376 return 0; 377 378 assert(ReplayState == (const void*)CallE && "Backtracked to the wrong call."); 379 (void)CallE; 380 381 return State->remove<ReplayWithoutInlining>(); 382} 383 384void ExprEngine::VisitCallExpr(const CallExpr *CE, ExplodedNode *Pred, 385 ExplodedNodeSet &dst) { 386 // Perform the previsit of the CallExpr. 387 ExplodedNodeSet dstPreVisit; 388 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, CE, *this); 389 390 // Get the callee kind. 391 CallEventKind K = classifyCallExpr(CE); 392 393 // Evaluate the function call. We try each of the checkers 394 // to see if the can evaluate the function call. 395 ExplodedNodeSet dstCallEvaluated; 396 for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end(); 397 I != E; ++I) { 398 ProgramStateRef State = (*I)->getState(); 399 const LocationContext *LCtx = (*I)->getLocationContext(); 400 401 // Evaluate the call. 402 switch (K) { 403 case CE_Function: 404 evalCall(dstCallEvaluated, *I, FunctionCall(CE, State, LCtx)); 405 break; 406 case CE_CXXMember: 407 evalCall(dstCallEvaluated, *I, CXXMemberCall(cast<CXXMemberCallExpr>(CE), 408 State, LCtx)); 409 break; 410 case CE_CXXMemberOperator: 411 evalCall(dstCallEvaluated, *I, 412 CXXMemberOperatorCall(cast<CXXOperatorCallExpr>(CE), 413 State, LCtx)); 414 break; 415 case CE_Block: 416 evalCall(dstCallEvaluated, *I, BlockCall(CE, State, LCtx)); 417 break; 418 default: 419 llvm_unreachable("Non-CallExpr CallEventKind"); 420 } 421 } 422 423 // Finally, perform the post-condition check of the CallExpr and store 424 // the created nodes in 'Dst'. 425 // Note that if the call was inlined, dstCallEvaluated will be empty. 426 // The post-CallExpr check will occur in processCallExit. 427 getCheckerManager().runCheckersForPostStmt(dst, dstCallEvaluated, CE, 428 *this); 429} 430 431void ExprEngine::evalCall(ExplodedNodeSet &Dst, ExplodedNode *Pred, 432 const SimpleCall &Call) { 433 // Run any pre-call checks using the generic call interface. 434 ExplodedNodeSet dstPreVisit; 435 getCheckerManager().runCheckersForPreCall(dstPreVisit, Pred, Call, *this); 436 437 // Actually evaluate the function call. We try each of the checkers 438 // to see if the can evaluate the function call, and get a callback at 439 // defaultEvalCall if all of them fail. 440 ExplodedNodeSet dstCallEvaluated; 441 getCheckerManager().runCheckersForEvalCall(dstCallEvaluated, dstPreVisit, 442 Call, *this); 443 444 // Finally, run any post-call checks. 445 getCheckerManager().runCheckersForPostCall(Dst, dstCallEvaluated, 446 Call, *this); 447} 448 449ProgramStateRef ExprEngine::bindReturnValue(const CallEvent &Call, 450 const LocationContext *LCtx, 451 ProgramStateRef State) { 452 const Expr *E = Call.getOriginExpr(); 453 if (!E) 454 return State; 455 456 // Some method families have known return values. 457 if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(&Call)) { 458 switch (Msg->getMethodFamily()) { 459 default: 460 break; 461 case OMF_autorelease: 462 case OMF_retain: 463 case OMF_self: { 464 // These methods return their receivers. 465 return State->BindExpr(E, LCtx, Msg->getReceiverSVal()); 466 } 467 } 468 } else if (const CXXConstructorCall *C = dyn_cast<CXXConstructorCall>(&Call)){ 469 return State->BindExpr(E, LCtx, C->getCXXThisVal()); 470 } 471 472 // Conjure a symbol if the return value is unknown. 473 QualType ResultTy = Call.getResultType(); 474 SValBuilder &SVB = getSValBuilder(); 475 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 476 SVal R = SVB.getConjuredSymbolVal(0, E, LCtx, ResultTy, Count); 477 return State->BindExpr(E, LCtx, R); 478} 479 480void ExprEngine::defaultEvalCall(NodeBuilder &Bldr, ExplodedNode *Pred, 481 const CallEvent &Call) { 482 ProgramStateRef State = 0; 483 const Expr *E = Call.getOriginExpr(); 484 485 // Try to inline the call. 486 // The origin expression here is just used as a kind of checksum; 487 // for CallEvents that do not have origin expressions, this should still be 488 // safe. 489 State = getInlineFailedState(Pred->getState(), E); 490 if (State == 0 && inlineCall(Call, Pred)) { 491 // If we inlined the call, the successor has been manually added onto 492 // the work list and we should not consider it for subsequent call 493 // handling steps. 494 Bldr.takeNodes(Pred); 495 return; 496 } 497 498 // If we can't inline it, handle the return value and invalidate the regions. 499 if (State == 0) 500 State = Pred->getState(); 501 502 // Invalidate any regions touched by the call. 503 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 504 State = Call.invalidateRegions(Count, State); 505 506 // Construct and bind the return value. 507 State = bindReturnValue(Call, Pred->getLocationContext(), State); 508 509 // And make the result node. 510 Bldr.generateNode(Call.getProgramPoint(), State, Pred); 511} 512 513void ExprEngine::VisitReturnStmt(const ReturnStmt *RS, ExplodedNode *Pred, 514 ExplodedNodeSet &Dst) { 515 516 ExplodedNodeSet dstPreVisit; 517 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, RS, *this); 518 519 StmtNodeBuilder B(dstPreVisit, Dst, *currentBuilderContext); 520 521 if (RS->getRetValue()) { 522 for (ExplodedNodeSet::iterator it = dstPreVisit.begin(), 523 ei = dstPreVisit.end(); it != ei; ++it) { 524 B.generateNode(RS, *it, (*it)->getState()); 525 } 526 } 527} 528