ExprEngineCallAndReturn.cpp revision 514f2c9dcb9e04b52929c5b141a6fe88bd68b33f
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/StaticAnalyzer/Core/CheckerManager.h" 15#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h" 16#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h" 17#include "llvm/Support/SaveAndRestore.h" 18#include "clang/AST/DeclCXX.h" 19 20using namespace clang; 21using namespace ento; 22 23void ExprEngine::processCallEnter(CallEnter CE, ExplodedNode *Pred) { 24 // Get the entry block in the CFG of the callee. 25 const StackFrameContext *calleeCtx = CE.getCalleeContext(); 26 const CFG *CalleeCFG = calleeCtx->getCFG(); 27 const CFGBlock *Entry = &(CalleeCFG->getEntry()); 28 29 // Validate the CFG. 30 assert(Entry->empty()); 31 assert(Entry->succ_size() == 1); 32 33 // Get the solitary sucessor. 34 const CFGBlock *Succ = *(Entry->succ_begin()); 35 36 // Construct an edge representing the starting location in the callee. 37 BlockEdge Loc(Entry, Succ, calleeCtx); 38 39 // Construct a new state which contains the mapping from actual to 40 // formal arguments. 41 const LocationContext *callerCtx = Pred->getLocationContext(); 42 ProgramStateRef state = Pred->getState()->enterStackFrame(callerCtx, 43 calleeCtx); 44 45 // Construct a new node and add it to the worklist. 46 bool isNew; 47 ExplodedNode *Node = G.getNode(Loc, state, false, &isNew); 48 Node->addPredecessor(Pred, G); 49 if (isNew) 50 Engine.getWorkList()->enqueue(Node); 51} 52 53static const ReturnStmt *getReturnStmt(const ExplodedNode *Node) { 54 while (Node) { 55 const ProgramPoint &PP = Node->getLocation(); 56 // Skip any BlockEdges. 57 if (isa<BlockEdge>(PP) || isa<CallExit>(PP)) { 58 assert(Node->pred_size() == 1); 59 Node = *Node->pred_begin(); 60 continue; 61 } 62 if (const StmtPoint *SP = dyn_cast<StmtPoint>(&PP)) { 63 const Stmt *S = SP->getStmt(); 64 return dyn_cast<ReturnStmt>(S); 65 } 66 break; 67 } 68 return 0; 69} 70 71void ExprEngine::processCallExit(ExplodedNode *Pred) { 72 ProgramStateRef state = Pred->getState(); 73 const StackFrameContext *calleeCtx = 74 Pred->getLocationContext()->getCurrentStackFrame(); 75 const LocationContext *callerCtx = calleeCtx->getParent(); 76 const Stmt *CE = calleeCtx->getCallSite(); 77 78 // If the callee returns an expression, bind its value to CallExpr. 79 if (const ReturnStmt *RS = getReturnStmt(Pred)) { 80 const LocationContext *LCtx = Pred->getLocationContext(); 81 SVal V = state->getSVal(RS, LCtx); 82 state = state->BindExpr(CE, callerCtx, V); 83 } 84 85 // Bind the constructed object value to CXXConstructExpr. 86 if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(CE)) { 87 const CXXThisRegion *ThisR = 88 getCXXThisRegion(CCE->getConstructor()->getParent(), calleeCtx); 89 90 SVal ThisV = state->getSVal(ThisR); 91 // Always bind the region to the CXXConstructExpr. 92 state = state->BindExpr(CCE, Pred->getLocationContext(), ThisV); 93 } 94 95 static SimpleProgramPointTag returnTag("ExprEngine : Call Return"); 96 PostStmt Loc(CE, callerCtx, &returnTag); 97 bool isNew; 98 ExplodedNode *N = G.getNode(Loc, state, false, &isNew); 99 N->addPredecessor(Pred, G); 100 if (!isNew) 101 return; 102 103 // Perform the post-condition check of the CallExpr. 104 ExplodedNodeSet Dst; 105 NodeBuilderContext Ctx(Engine, calleeCtx->getCallSiteBlock(), N); 106 SaveAndRestore<const NodeBuilderContext*> NBCSave(currentBuilderContext, 107 &Ctx); 108 SaveAndRestore<unsigned> CBISave(currentStmtIdx, calleeCtx->getIndex()); 109 110 getCheckerManager().runCheckersForPostStmt(Dst, N, CE, *this, 111 /* wasInlined */ true); 112 113 // Enqueue the next element in the block. 114 for (ExplodedNodeSet::iterator I = Dst.begin(), E = Dst.end(); I != E; ++I) { 115 Engine.getWorkList()->enqueue(*I, 116 calleeCtx->getCallSiteBlock(), 117 calleeCtx->getIndex()+1); 118 } 119} 120 121static unsigned getNumberStackFrames(const LocationContext *LCtx) { 122 unsigned count = 0; 123 while (LCtx) { 124 if (isa<StackFrameContext>(LCtx)) 125 ++count; 126 LCtx = LCtx->getParent(); 127 } 128 return count; 129} 130 131// Determine if we should inline the call. 132static bool shouldInline(const FunctionDecl *FD, ExplodedNode *Pred, 133 AnalysisManager &AMgr) { 134 AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(FD); 135 const CFG *CalleeCFG = CalleeADC->getCFG(); 136 137 if (getNumberStackFrames(Pred->getLocationContext()) 138 == AMgr.InlineMaxStackDepth) 139 return false; 140 141 if (CalleeCFG->getNumBlockIDs() > AMgr.InlineMaxFunctionSize) 142 return false; 143 144 return true; 145} 146 147bool ExprEngine::InlineCall(ExplodedNodeSet &Dst, 148 const CallExpr *CE, 149 ExplodedNode *Pred) { 150 ProgramStateRef state = Pred->getState(); 151 const Expr *Callee = CE->getCallee(); 152 const FunctionDecl *FD = 153 state->getSVal(Callee, Pred->getLocationContext()).getAsFunctionDecl(); 154 if (!FD || !FD->hasBody(FD)) 155 return false; 156 157 switch (CE->getStmtClass()) { 158 default: 159 // FIXME: Handle C++. 160 break; 161 case Stmt::CallExprClass: { 162 if (!shouldInline(FD, Pred, AMgr)) 163 return false; 164 165 // Construct a new stack frame for the callee. 166 AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(FD); 167 const StackFrameContext *CallerSFC = 168 Pred->getLocationContext()->getCurrentStackFrame(); 169 const StackFrameContext *CalleeSFC = 170 CalleeADC->getStackFrame(CallerSFC, CE, 171 currentBuilderContext->getBlock(), 172 currentStmtIdx); 173 174 CallEnter Loc(CE, CalleeSFC, Pred->getLocationContext()); 175 bool isNew; 176 ExplodedNode *N = G.getNode(Loc, state, false, &isNew); 177 N->addPredecessor(Pred, G); 178 if (isNew) 179 Engine.getWorkList()->enqueue(N); 180 return true; 181 } 182 } 183 return false; 184} 185 186static bool isPointerToConst(const ParmVarDecl *ParamDecl) { 187 QualType PointeeTy = ParamDecl->getOriginalType()->getPointeeType(); 188 if (PointeeTy != QualType() && PointeeTy.isConstQualified() && 189 !PointeeTy->isAnyPointerType() && !PointeeTy->isReferenceType()) { 190 return true; 191 } 192 return false; 193} 194 195// Try to retrieve the function declaration and find the function parameter 196// types which are pointers/references to a non-pointer const. 197// We do not invalidate the corresponding argument regions. 198static void findPtrToConstParams(llvm::SmallSet<unsigned, 1> &PreserveArgs, 199 const CallOrObjCMessage &Call) { 200 const Decl *CallDecl = Call.getDecl(); 201 if (!CallDecl) 202 return; 203 204 if (const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(CallDecl)) { 205 const IdentifierInfo *II = FDecl->getIdentifier(); 206 207 // List the cases, where the region should be invalidated even if the 208 // argument is const. 209 if (II) { 210 StringRef FName = II->getName(); 211 // - 'int pthread_setspecific(ptheread_key k, const void *)' stores a 212 // value into thread local storage. The value can later be retrieved with 213 // 'void *ptheread_getspecific(pthread_key)'. So even thought the 214 // parameter is 'const void *', the region escapes through the call. 215 // - funopen - sets a buffer for future IO calls. 216 // - ObjC functions that end with "NoCopy" can free memory, of the passed 217 // in buffer. 218 // - Many CF containers allow objects to escape through custom 219 // allocators/deallocators upon container construction. 220 if (FName == "pthread_setspecific" || 221 FName == "funopen" || 222 FName.endswith("NoCopy") || 223 Call.isCFCGAllowingEscape(FName)) 224 return; 225 } 226 227 for (unsigned Idx = 0, E = Call.getNumArgs(); Idx != E; ++Idx) { 228 if (FDecl && Idx < FDecl->getNumParams()) { 229 if (isPointerToConst(FDecl->getParamDecl(Idx))) 230 PreserveArgs.insert(Idx); 231 } 232 } 233 return; 234 } 235 236 if (const ObjCMethodDecl *MDecl = dyn_cast<ObjCMethodDecl>(CallDecl)) { 237 assert(MDecl->param_size() <= Call.getNumArgs()); 238 unsigned Idx = 0; 239 for (clang::ObjCMethodDecl::param_const_iterator 240 I = MDecl->param_begin(), E = MDecl->param_end(); I != E; ++I, ++Idx) { 241 if (isPointerToConst(*I)) 242 PreserveArgs.insert(Idx); 243 } 244 return; 245 } 246} 247 248ProgramStateRef 249ExprEngine::invalidateArguments(ProgramStateRef State, 250 const CallOrObjCMessage &Call, 251 const LocationContext *LC) { 252 SmallVector<const MemRegion *, 8> RegionsToInvalidate; 253 254 if (Call.isObjCMessage()) { 255 // Invalidate all instance variables of the receiver of an ObjC message. 256 // FIXME: We should be able to do better with inter-procedural analysis. 257 if (const MemRegion *MR = Call.getInstanceMessageReceiver(LC).getAsRegion()) 258 RegionsToInvalidate.push_back(MR); 259 260 } else if (Call.isCXXCall()) { 261 // Invalidate all instance variables for the callee of a C++ method call. 262 // FIXME: We should be able to do better with inter-procedural analysis. 263 // FIXME: We can probably do better for const versus non-const methods. 264 if (const MemRegion *Callee = Call.getCXXCallee().getAsRegion()) 265 RegionsToInvalidate.push_back(Callee); 266 267 } else if (Call.isFunctionCall()) { 268 // Block calls invalidate all captured-by-reference values. 269 SVal CalleeVal = Call.getFunctionCallee(); 270 if (const MemRegion *Callee = CalleeVal.getAsRegion()) { 271 if (isa<BlockDataRegion>(Callee)) 272 RegionsToInvalidate.push_back(Callee); 273 } 274 } 275 276 // Indexes of arguments whose values will be preserved by the call. 277 llvm::SmallSet<unsigned, 1> PreserveArgs; 278 findPtrToConstParams(PreserveArgs, Call); 279 280 for (unsigned idx = 0, e = Call.getNumArgs(); idx != e; ++idx) { 281 if (PreserveArgs.count(idx)) 282 continue; 283 284 SVal V = Call.getArgSVal(idx); 285 286 // If we are passing a location wrapped as an integer, unwrap it and 287 // invalidate the values referred by the location. 288 if (nonloc::LocAsInteger *Wrapped = dyn_cast<nonloc::LocAsInteger>(&V)) 289 V = Wrapped->getLoc(); 290 else if (!isa<Loc>(V)) 291 continue; 292 293 if (const MemRegion *R = V.getAsRegion()) { 294 // Invalidate the value of the variable passed by reference. 295 296 // Are we dealing with an ElementRegion? If the element type is 297 // a basic integer type (e.g., char, int) and the underlying region 298 // is a variable region then strip off the ElementRegion. 299 // FIXME: We really need to think about this for the general case 300 // as sometimes we are reasoning about arrays and other times 301 // about (char*), etc., is just a form of passing raw bytes. 302 // e.g., void *p = alloca(); foo((char*)p); 303 if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) { 304 // Checking for 'integral type' is probably too promiscuous, but 305 // we'll leave it in for now until we have a systematic way of 306 // handling all of these cases. Eventually we need to come up 307 // with an interface to StoreManager so that this logic can be 308 // appropriately delegated to the respective StoreManagers while 309 // still allowing us to do checker-specific logic (e.g., 310 // invalidating reference counts), probably via callbacks. 311 if (ER->getElementType()->isIntegralOrEnumerationType()) { 312 const MemRegion *superReg = ER->getSuperRegion(); 313 if (isa<VarRegion>(superReg) || isa<FieldRegion>(superReg) || 314 isa<ObjCIvarRegion>(superReg)) 315 R = cast<TypedRegion>(superReg); 316 } 317 // FIXME: What about layers of ElementRegions? 318 } 319 320 // Mark this region for invalidation. We batch invalidate regions 321 // below for efficiency. 322 RegionsToInvalidate.push_back(R); 323 } else { 324 // Nuke all other arguments passed by reference. 325 // FIXME: is this necessary or correct? This handles the non-Region 326 // cases. Is it ever valid to store to these? 327 State = State->unbindLoc(cast<Loc>(V)); 328 } 329 } 330 331 // Invalidate designated regions using the batch invalidation API. 332 333 // FIXME: We can have collisions on the conjured symbol if the 334 // expression *I also creates conjured symbols. We probably want 335 // to identify conjured symbols by an expression pair: the enclosing 336 // expression (the context) and the expression itself. This should 337 // disambiguate conjured symbols. 338 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 339 StoreManager::InvalidatedSymbols IS; 340 341 // NOTE: Even if RegionsToInvalidate is empty, we may still invalidate 342 // global variables. 343 return State->invalidateRegions(RegionsToInvalidate, 344 Call.getOriginExpr(), Count, LC, 345 &IS, &Call); 346 347} 348 349// For now, skip inlining variadic functions. 350// We also don't inline blocks. 351static bool shouldInlineCall(const CallExpr *CE, ExprEngine &Eng) { 352 if (!Eng.getAnalysisManager().shouldInlineCall()) 353 return false; 354 QualType callee = CE->getCallee()->getType(); 355 const FunctionProtoType *FT = 0; 356 if (const PointerType *PT = callee->getAs<PointerType>()) 357 FT = dyn_cast<FunctionProtoType>(PT->getPointeeType()); 358 else if (const BlockPointerType *BT = callee->getAs<BlockPointerType>()) { 359 // FIXME: inline blocks. 360 // FT = dyn_cast<FunctionProtoType>(BT->getPointeeType()); 361 (void) BT; 362 return false; 363 } 364 365 // If we have no prototype, assume the function is okay. 366 if (!FT) 367 return true; 368 369 // Skip inlining of variadic functions. 370 return !FT->isVariadic(); 371} 372 373void ExprEngine::VisitCallExpr(const CallExpr *CE, ExplodedNode *Pred, 374 ExplodedNodeSet &dst) { 375 // Perform the previsit of the CallExpr. 376 ExplodedNodeSet dstPreVisit; 377 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, CE, *this); 378 379 // Now evaluate the call itself. 380 class DefaultEval : public GraphExpander { 381 ExprEngine &Eng; 382 const CallExpr *CE; 383 public: 384 385 DefaultEval(ExprEngine &eng, const CallExpr *ce) 386 : Eng(eng), CE(ce) {} 387 virtual void expandGraph(ExplodedNodeSet &Dst, ExplodedNode *Pred) { 388 // Should we inline the call? 389 if (shouldInlineCall(CE, Eng) && 390 Eng.InlineCall(Dst, CE, Pred)) { 391 return; 392 } 393 394 // First handle the return value. 395 StmtNodeBuilder Bldr(Pred, Dst, *Eng.currentBuilderContext); 396 397 // Get the callee. 398 const Expr *Callee = CE->getCallee()->IgnoreParens(); 399 ProgramStateRef state = Pred->getState(); 400 SVal L = state->getSVal(Callee, Pred->getLocationContext()); 401 402 // Figure out the result type. We do this dance to handle references. 403 QualType ResultTy; 404 if (const FunctionDecl *FD = L.getAsFunctionDecl()) 405 ResultTy = FD->getResultType(); 406 else 407 ResultTy = CE->getType(); 408 409 if (CE->isLValue()) 410 ResultTy = Eng.getContext().getPointerType(ResultTy); 411 412 // Conjure a symbol value to use as the result. 413 SValBuilder &SVB = Eng.getSValBuilder(); 414 unsigned Count = Eng.currentBuilderContext->getCurrentBlockCount(); 415 const LocationContext *LCtx = Pred->getLocationContext(); 416 SVal RetVal = SVB.getConjuredSymbolVal(0, CE, LCtx, ResultTy, Count); 417 418 // Generate a new state with the return value set. 419 state = state->BindExpr(CE, LCtx, RetVal); 420 421 // Invalidate the arguments. 422 state = Eng.invalidateArguments(state, CallOrObjCMessage(CE, state, LCtx), 423 LCtx); 424 425 // And make the result node. 426 Bldr.generateNode(CE, Pred, state); 427 } 428 }; 429 430 // Finally, evaluate the function call. We try each of the checkers 431 // to see if the can evaluate the function call. 432 ExplodedNodeSet dstCallEvaluated; 433 DefaultEval defEval(*this, CE); 434 getCheckerManager().runCheckersForEvalCall(dstCallEvaluated, 435 dstPreVisit, 436 CE, *this, &defEval); 437 438 // Finally, perform the post-condition check of the CallExpr and store 439 // the created nodes in 'Dst'. 440 getCheckerManager().runCheckersForPostStmt(dst, dstCallEvaluated, CE, 441 *this); 442} 443 444void ExprEngine::VisitReturnStmt(const ReturnStmt *RS, ExplodedNode *Pred, 445 ExplodedNodeSet &Dst) { 446 447 ExplodedNodeSet dstPreVisit; 448 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, RS, *this); 449 450 StmtNodeBuilder B(dstPreVisit, Dst, *currentBuilderContext); 451 452 if (RS->getRetValue()) { 453 for (ExplodedNodeSet::iterator it = dstPreVisit.begin(), 454 ei = dstPreVisit.end(); it != ei; ++it) { 455 B.generateNode(RS, *it, (*it)->getState()); 456 } 457 } 458} 459