ExprEngineCallAndReturn.cpp revision 0d389b819c33bdf0375694a8f141c8f02e002b18
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 "clang/Analysis/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); 111 112 // Enqueue the next element in the block. 113 for (ExplodedNodeSet::iterator I = Dst.begin(), E = Dst.end(); I != E; ++I) { 114 Engine.getWorkList()->enqueue(*I, 115 calleeCtx->getCallSiteBlock(), 116 calleeCtx->getIndex()+1); 117 } 118} 119 120static unsigned getNumberStackFrames(const LocationContext *LCtx) { 121 unsigned count = 0; 122 while (LCtx) { 123 if (isa<StackFrameContext>(LCtx)) 124 ++count; 125 LCtx = LCtx->getParent(); 126 } 127 return count; 128} 129 130bool ExprEngine::InlineCall(ExplodedNodeSet &Dst, 131 const CallExpr *CE, 132 ExplodedNode *Pred) { 133 ProgramStateRef state = Pred->getState(); 134 const Expr *Callee = CE->getCallee(); 135 const FunctionDecl *FD = 136 state->getSVal(Callee, Pred->getLocationContext()).getAsFunctionDecl(); 137 if (!FD || !FD->hasBody(FD)) 138 return false; 139 140 switch (CE->getStmtClass()) { 141 default: 142 // FIXME: Handle C++. 143 break; 144 case Stmt::CallExprClass: { 145 // Cap the stack depth at 4 calls (5 stack frames, base + 4 calls). 146 // These heuristics are a WIP. 147 if (getNumberStackFrames(Pred->getLocationContext()) == 5) 148 return false; 149 150 // Construct a new stack frame for the callee. 151 AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(FD); 152 const StackFrameContext *CallerSFC = 153 Pred->getLocationContext()->getCurrentStackFrame(); 154 const StackFrameContext *CalleeSFC = 155 CalleeADC->getStackFrame(CallerSFC, CE, 156 currentBuilderContext->getBlock(), 157 currentStmtIdx); 158 159 CallEnter Loc(CE, CalleeSFC, Pred->getLocationContext()); 160 bool isNew; 161 ExplodedNode *N = G.getNode(Loc, state, false, &isNew); 162 N->addPredecessor(Pred, G); 163 if (isNew) 164 Engine.getWorkList()->enqueue(N); 165 return true; 166 } 167 } 168 return false; 169} 170 171static bool isPointerToConst(const ParmVarDecl *ParamDecl) { 172 QualType PointeeTy = ParamDecl->getOriginalType()->getPointeeType(); 173 if (PointeeTy != QualType() && PointeeTy.isConstQualified() && 174 !PointeeTy->isAnyPointerType() && !PointeeTy->isReferenceType()) { 175 return true; 176 } 177 return false; 178} 179 180// Try to retrieve the function declaration and find the function parameter 181// types which are pointers/references to a non-pointer const. 182// We do not invalidate the corresponding argument regions. 183static void findPtrToConstParams(llvm::SmallSet<unsigned, 1> &PreserveArgs, 184 const CallOrObjCMessage &Call) { 185 const Decl *CallDecl = Call.getDecl(); 186 if (!CallDecl) 187 return; 188 189 if (const FunctionDecl *FDecl = dyn_cast<FunctionDecl>(CallDecl)) { 190 const IdentifierInfo *II = FDecl->getIdentifier(); 191 192 // List the cases, where the region should be invalidated even if the 193 // argument is const. 194 if (II) { 195 StringRef FName = II->getName(); 196 // 'int pthread_setspecific(ptheread_key k, const void *)' stores a value 197 // into thread local storage. The value can later be retrieved with 198 // 'void *ptheread_getspecific(pthread_key)'. So even thought the 199 // parameter is 'const void *', the region escapes through the call. 200 if (FName.equals("pthread_setspecific")) 201 return; 202 } 203 204 for (unsigned Idx = 0, E = Call.getNumArgs(); Idx != E; ++Idx) { 205 if (FDecl && Idx < FDecl->getNumParams()) { 206 if (isPointerToConst(FDecl->getParamDecl(Idx))) 207 PreserveArgs.insert(Idx); 208 } 209 } 210 return; 211 } 212 213 if (const ObjCMethodDecl *MDecl = dyn_cast<ObjCMethodDecl>(CallDecl)) { 214 assert(MDecl->param_size() <= Call.getNumArgs()); 215 unsigned Idx = 0; 216 for (clang::ObjCMethodDecl::param_const_iterator 217 I = MDecl->param_begin(), E = MDecl->param_end(); I != E; ++I, ++Idx) { 218 if (isPointerToConst(*I)) 219 PreserveArgs.insert(Idx); 220 } 221 return; 222 } 223} 224 225ProgramStateRef 226ExprEngine::invalidateArguments(ProgramStateRef State, 227 const CallOrObjCMessage &Call, 228 const LocationContext *LC) { 229 SmallVector<const MemRegion *, 8> RegionsToInvalidate; 230 231 if (Call.isObjCMessage()) { 232 // Invalidate all instance variables of the receiver of an ObjC message. 233 // FIXME: We should be able to do better with inter-procedural analysis. 234 if (const MemRegion *MR = Call.getInstanceMessageReceiver(LC).getAsRegion()) 235 RegionsToInvalidate.push_back(MR); 236 237 } else if (Call.isCXXCall()) { 238 // Invalidate all instance variables for the callee of a C++ method call. 239 // FIXME: We should be able to do better with inter-procedural analysis. 240 // FIXME: We can probably do better for const versus non-const methods. 241 if (const MemRegion *Callee = Call.getCXXCallee().getAsRegion()) 242 RegionsToInvalidate.push_back(Callee); 243 244 } else if (Call.isFunctionCall()) { 245 // Block calls invalidate all captured-by-reference values. 246 SVal CalleeVal = Call.getFunctionCallee(); 247 if (const MemRegion *Callee = CalleeVal.getAsRegion()) { 248 if (isa<BlockDataRegion>(Callee)) 249 RegionsToInvalidate.push_back(Callee); 250 } 251 } 252 253 // Indexes of arguments whose values will be preserved by the call. 254 llvm::SmallSet<unsigned, 1> PreserveArgs; 255 findPtrToConstParams(PreserveArgs, Call); 256 257 for (unsigned idx = 0, e = Call.getNumArgs(); idx != e; ++idx) { 258 if (PreserveArgs.count(idx)) 259 continue; 260 261 SVal V = Call.getArgSVal(idx); 262 263 // If we are passing a location wrapped as an integer, unwrap it and 264 // invalidate the values referred by the location. 265 if (nonloc::LocAsInteger *Wrapped = dyn_cast<nonloc::LocAsInteger>(&V)) 266 V = Wrapped->getLoc(); 267 else if (!isa<Loc>(V)) 268 continue; 269 270 if (const MemRegion *R = V.getAsRegion()) { 271 // Invalidate the value of the variable passed by reference. 272 273 // Are we dealing with an ElementRegion? If the element type is 274 // a basic integer type (e.g., char, int) and the underlying region 275 // is a variable region then strip off the ElementRegion. 276 // FIXME: We really need to think about this for the general case 277 // as sometimes we are reasoning about arrays and other times 278 // about (char*), etc., is just a form of passing raw bytes. 279 // e.g., void *p = alloca(); foo((char*)p); 280 if (const ElementRegion *ER = dyn_cast<ElementRegion>(R)) { 281 // Checking for 'integral type' is probably too promiscuous, but 282 // we'll leave it in for now until we have a systematic way of 283 // handling all of these cases. Eventually we need to come up 284 // with an interface to StoreManager so that this logic can be 285 // appropriately delegated to the respective StoreManagers while 286 // still allowing us to do checker-specific logic (e.g., 287 // invalidating reference counts), probably via callbacks. 288 if (ER->getElementType()->isIntegralOrEnumerationType()) { 289 const MemRegion *superReg = ER->getSuperRegion(); 290 if (isa<VarRegion>(superReg) || isa<FieldRegion>(superReg) || 291 isa<ObjCIvarRegion>(superReg)) 292 R = cast<TypedRegion>(superReg); 293 } 294 // FIXME: What about layers of ElementRegions? 295 } 296 297 // Mark this region for invalidation. We batch invalidate regions 298 // below for efficiency. 299 RegionsToInvalidate.push_back(R); 300 } else { 301 // Nuke all other arguments passed by reference. 302 // FIXME: is this necessary or correct? This handles the non-Region 303 // cases. Is it ever valid to store to these? 304 State = State->unbindLoc(cast<Loc>(V)); 305 } 306 } 307 308 // Invalidate designated regions using the batch invalidation API. 309 310 // FIXME: We can have collisions on the conjured symbol if the 311 // expression *I also creates conjured symbols. We probably want 312 // to identify conjured symbols by an expression pair: the enclosing 313 // expression (the context) and the expression itself. This should 314 // disambiguate conjured symbols. 315 unsigned Count = currentBuilderContext->getCurrentBlockCount(); 316 StoreManager::InvalidatedSymbols IS; 317 318 // NOTE: Even if RegionsToInvalidate is empty, we may still invalidate 319 // global variables. 320 return State->invalidateRegions(RegionsToInvalidate, 321 Call.getOriginExpr(), Count, LC, 322 &IS, &Call); 323 324} 325 326// For now, skip inlining variadic functions. 327// We also don't inline blocks. 328static bool shouldInlineCall(const CallExpr *CE, ExprEngine &Eng) { 329 if (!Eng.getAnalysisManager().shouldInlineCall()) 330 return false; 331 QualType callee = CE->getCallee()->getType(); 332 const FunctionProtoType *FT = 0; 333 if (const PointerType *PT = callee->getAs<PointerType>()) 334 FT = dyn_cast<FunctionProtoType>(PT->getPointeeType()); 335 else if (const BlockPointerType *BT = callee->getAs<BlockPointerType>()) { 336 // FIXME: inline blocks. 337 // FT = dyn_cast<FunctionProtoType>(BT->getPointeeType()); 338 (void) BT; 339 return false; 340 } 341 342 // If we have no prototype, assume the function is okay. 343 if (!FT) 344 return true; 345 346 // Skip inlining of variadic functions. 347 return !FT->isVariadic(); 348} 349 350void ExprEngine::VisitCallExpr(const CallExpr *CE, ExplodedNode *Pred, 351 ExplodedNodeSet &dst) { 352 // Perform the previsit of the CallExpr. 353 ExplodedNodeSet dstPreVisit; 354 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, CE, *this); 355 356 // Now evaluate the call itself. 357 class DefaultEval : public GraphExpander { 358 ExprEngine &Eng; 359 const CallExpr *CE; 360 public: 361 362 DefaultEval(ExprEngine &eng, const CallExpr *ce) 363 : Eng(eng), CE(ce) {} 364 virtual void expandGraph(ExplodedNodeSet &Dst, ExplodedNode *Pred) { 365 // Should we inline the call? 366 if (shouldInlineCall(CE, Eng) && 367 Eng.InlineCall(Dst, CE, Pred)) { 368 return; 369 } 370 371 // First handle the return value. 372 StmtNodeBuilder Bldr(Pred, Dst, *Eng.currentBuilderContext); 373 374 // Get the callee. 375 const Expr *Callee = CE->getCallee()->IgnoreParens(); 376 ProgramStateRef state = Pred->getState(); 377 SVal L = state->getSVal(Callee, Pred->getLocationContext()); 378 379 // Figure out the result type. We do this dance to handle references. 380 QualType ResultTy; 381 if (const FunctionDecl *FD = L.getAsFunctionDecl()) 382 ResultTy = FD->getResultType(); 383 else 384 ResultTy = CE->getType(); 385 386 if (CE->isLValue()) 387 ResultTy = Eng.getContext().getPointerType(ResultTy); 388 389 // Conjure a symbol value to use as the result. 390 SValBuilder &SVB = Eng.getSValBuilder(); 391 unsigned Count = Eng.currentBuilderContext->getCurrentBlockCount(); 392 const LocationContext *LCtx = Pred->getLocationContext(); 393 SVal RetVal = SVB.getConjuredSymbolVal(0, CE, LCtx, ResultTy, Count); 394 395 // Generate a new state with the return value set. 396 state = state->BindExpr(CE, LCtx, RetVal); 397 398 // Invalidate the arguments. 399 state = Eng.invalidateArguments(state, CallOrObjCMessage(CE, state, LCtx), 400 LCtx); 401 402 // And make the result node. 403 Bldr.generateNode(CE, Pred, state); 404 } 405 }; 406 407 // Finally, evaluate the function call. We try each of the checkers 408 // to see if the can evaluate the function call. 409 ExplodedNodeSet dstCallEvaluated; 410 DefaultEval defEval(*this, CE); 411 getCheckerManager().runCheckersForEvalCall(dstCallEvaluated, 412 dstPreVisit, 413 CE, *this, &defEval); 414 415 // Finally, perform the post-condition check of the CallExpr and store 416 // the created nodes in 'Dst'. 417 getCheckerManager().runCheckersForPostStmt(dst, dstCallEvaluated, CE, 418 *this); 419} 420 421void ExprEngine::VisitReturnStmt(const ReturnStmt *RS, ExplodedNode *Pred, 422 ExplodedNodeSet &Dst) { 423 424 ExplodedNodeSet dstPreVisit; 425 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, RS, *this); 426 427 StmtNodeBuilder B(dstPreVisit, Dst, *currentBuilderContext); 428 429 if (RS->getRetValue()) { 430 for (ExplodedNodeSet::iterator it = dstPreVisit.begin(), 431 ei = dstPreVisit.end(); it != ei; ++it) { 432 B.generateNode(RS, *it, (*it)->getState()); 433 } 434 } 435 else { 436 B.takeNodes(dstPreVisit); 437 } 438} 439