JumpDiagnostics.cpp revision 029d28449c4adb5ce92b58b5a57eeca6e396e404
1//===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- 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 implements the JumpScopeChecker class, which is used to diagnose 11// jumps that enter a protected scope in an invalid way. 12// 13//===----------------------------------------------------------------------===// 14 15#include "clang/Sema/SemaInternal.h" 16#include "clang/AST/DeclCXX.h" 17#include "clang/AST/Expr.h" 18#include "clang/AST/ExprCXX.h" 19#include "clang/AST/StmtObjC.h" 20#include "clang/AST/StmtCXX.h" 21#include "llvm/ADT/BitVector.h" 22using namespace clang; 23 24namespace { 25 26/// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps 27/// into VLA and other protected scopes. For example, this rejects: 28/// goto L; 29/// int a[n]; 30/// L: 31/// 32class JumpScopeChecker { 33 Sema &S; 34 35 /// GotoScope - This is a record that we use to keep track of all of the 36 /// scopes that are introduced by VLAs and other things that scope jumps like 37 /// gotos. This scope tree has nothing to do with the source scope tree, 38 /// because you can have multiple VLA scopes per compound statement, and most 39 /// compound statements don't introduce any scopes. 40 struct GotoScope { 41 /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for 42 /// the parent scope is the function body. 43 unsigned ParentScope; 44 45 /// InDiag - The note to emit if there is a jump into this scope. 46 unsigned InDiag; 47 48 /// OutDiag - The note to emit if there is an indirect jump out 49 /// of this scope. Direct jumps always clean up their current scope 50 /// in an orderly way. 51 unsigned OutDiag; 52 53 /// Loc - Location to emit the diagnostic. 54 SourceLocation Loc; 55 56 GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag, 57 SourceLocation L) 58 : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {} 59 }; 60 61 SmallVector<GotoScope, 48> Scopes; 62 llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes; 63 SmallVector<Stmt*, 16> Jumps; 64 65 SmallVector<IndirectGotoStmt*, 4> IndirectJumps; 66 SmallVector<LabelDecl*, 4> IndirectJumpTargets; 67public: 68 JumpScopeChecker(Stmt *Body, Sema &S); 69private: 70 void BuildScopeInformation(Decl *D, unsigned &ParentScope); 71 void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl, 72 unsigned &ParentScope); 73 void BuildScopeInformation(Stmt *S, unsigned &origParentScope); 74 75 void VerifyJumps(); 76 void VerifyIndirectJumps(); 77 void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes); 78 void DiagnoseIndirectJump(IndirectGotoStmt *IG, unsigned IGScope, 79 LabelDecl *Target, unsigned TargetScope); 80 void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc, 81 unsigned JumpDiag, unsigned JumpDiagWarning, 82 unsigned JumpDiagCXX98Compat); 83 84 unsigned GetDeepestCommonScope(unsigned A, unsigned B); 85}; 86} // end anonymous namespace 87 88 89JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) { 90 // Add a scope entry for function scope. 91 Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation())); 92 93 // Build information for the top level compound statement, so that we have a 94 // defined scope record for every "goto" and label. 95 unsigned BodyParentScope = 0; 96 BuildScopeInformation(Body, BodyParentScope); 97 98 // Check that all jumps we saw are kosher. 99 VerifyJumps(); 100 VerifyIndirectJumps(); 101} 102 103/// GetDeepestCommonScope - Finds the innermost scope enclosing the 104/// two scopes. 105unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) { 106 while (A != B) { 107 // Inner scopes are created after outer scopes and therefore have 108 // higher indices. 109 if (A < B) { 110 assert(Scopes[B].ParentScope < B); 111 B = Scopes[B].ParentScope; 112 } else { 113 assert(Scopes[A].ParentScope < A); 114 A = Scopes[A].ParentScope; 115 } 116 } 117 return A; 118} 119 120typedef std::pair<unsigned,unsigned> ScopePair; 121 122/// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a 123/// diagnostic that should be emitted if control goes over it. If not, return 0. 124static ScopePair GetDiagForGotoScopeDecl(ASTContext &Context, const Decl *D) { 125 if (const VarDecl *VD = dyn_cast<VarDecl>(D)) { 126 unsigned InDiag = 0, OutDiag = 0; 127 if (VD->getType()->isVariablyModifiedType()) 128 InDiag = diag::note_protected_by_vla; 129 130 if (VD->hasAttr<BlocksAttr>()) 131 return ScopePair(diag::note_protected_by___block, 132 diag::note_exits___block); 133 134 if (VD->hasAttr<CleanupAttr>()) 135 return ScopePair(diag::note_protected_by_cleanup, 136 diag::note_exits_cleanup); 137 138 if (Context.getLangOpts().ObjCAutoRefCount && VD->hasLocalStorage()) { 139 switch (VD->getType().getObjCLifetime()) { 140 case Qualifiers::OCL_None: 141 case Qualifiers::OCL_ExplicitNone: 142 case Qualifiers::OCL_Autoreleasing: 143 break; 144 145 case Qualifiers::OCL_Strong: 146 case Qualifiers::OCL_Weak: 147 return ScopePair(diag::note_protected_by_objc_ownership, 148 diag::note_exits_objc_ownership); 149 } 150 } 151 152 if (Context.getLangOpts().CPlusPlus && VD->hasLocalStorage()) { 153 // C++11 [stmt.dcl]p3: 154 // A program that jumps from a point where a variable with automatic 155 // storage duration is not in scope to a point where it is in scope 156 // is ill-formed unless the variable has scalar type, class type with 157 // a trivial default constructor and a trivial destructor, a 158 // cv-qualified version of one of these types, or an array of one of 159 // the preceding types and is declared without an initializer. 160 161 // C++03 [stmt.dcl.p3: 162 // A program that jumps from a point where a local variable 163 // with automatic storage duration is not in scope to a point 164 // where it is in scope is ill-formed unless the variable has 165 // POD type and is declared without an initializer. 166 167 if (const Expr *init = VD->getInit()) { 168 // We actually give variables of record type (or array thereof) 169 // an initializer even if that initializer only calls a trivial 170 // ctor. Detect that case. 171 // FIXME: With generalized initializer lists, this may 172 // classify "X x{};" as having no initializer. 173 unsigned inDiagToUse = diag::note_protected_by_variable_init; 174 175 const CXXRecordDecl *record = 0; 176 177 if (const CXXConstructExpr *cce = dyn_cast<CXXConstructExpr>(init)) { 178 const CXXConstructorDecl *ctor = cce->getConstructor(); 179 record = ctor->getParent(); 180 181 if (ctor->isTrivial() && ctor->isDefaultConstructor()) { 182 if (!record->hasTrivialDestructor()) 183 inDiagToUse = diag::note_protected_by_variable_nontriv_destructor; 184 else if (!record->isPOD()) 185 inDiagToUse = diag::note_protected_by_variable_non_pod; 186 else 187 inDiagToUse = 0; 188 } 189 } else if (VD->getType()->isArrayType()) { 190 record = VD->getType()->getBaseElementTypeUnsafe() 191 ->getAsCXXRecordDecl(); 192 } 193 194 if (inDiagToUse) 195 InDiag = inDiagToUse; 196 197 // Also object to indirect jumps which leave scopes with dtors. 198 if (record && !record->hasTrivialDestructor()) 199 OutDiag = diag::note_exits_dtor; 200 } 201 } 202 203 return ScopePair(InDiag, OutDiag); 204 } 205 206 if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) { 207 if (TD->getUnderlyingType()->isVariablyModifiedType()) 208 return ScopePair(diag::note_protected_by_vla_typedef, 0); 209 } 210 211 if (const TypeAliasDecl *TD = dyn_cast<TypeAliasDecl>(D)) { 212 if (TD->getUnderlyingType()->isVariablyModifiedType()) 213 return ScopePair(diag::note_protected_by_vla_type_alias, 0); 214 } 215 216 return ScopePair(0U, 0U); 217} 218 219/// \brief Build scope information for a declaration that is part of a DeclStmt. 220void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) { 221 // If this decl causes a new scope, push and switch to it. 222 std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S.Context, D); 223 if (Diags.first || Diags.second) { 224 Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second, 225 D->getLocation())); 226 ParentScope = Scopes.size()-1; 227 } 228 229 // If the decl has an initializer, walk it with the potentially new 230 // scope we just installed. 231 if (VarDecl *VD = dyn_cast<VarDecl>(D)) 232 if (Expr *Init = VD->getInit()) 233 BuildScopeInformation(Init, ParentScope); 234} 235 236/// \brief Build scope information for a captured block literal variables. 237void JumpScopeChecker::BuildScopeInformation(VarDecl *D, 238 const BlockDecl *BDecl, 239 unsigned &ParentScope) { 240 // exclude captured __block variables; there's no destructor 241 // associated with the block literal for them. 242 if (D->hasAttr<BlocksAttr>()) 243 return; 244 QualType T = D->getType(); 245 QualType::DestructionKind destructKind = T.isDestructedType(); 246 if (destructKind != QualType::DK_none) { 247 std::pair<unsigned,unsigned> Diags; 248 switch (destructKind) { 249 case QualType::DK_cxx_destructor: 250 Diags = ScopePair(diag::note_enters_block_captures_cxx_obj, 251 diag::note_exits_block_captures_cxx_obj); 252 break; 253 case QualType::DK_objc_strong_lifetime: 254 Diags = ScopePair(diag::note_enters_block_captures_strong, 255 diag::note_exits_block_captures_strong); 256 break; 257 case QualType::DK_objc_weak_lifetime: 258 Diags = ScopePair(diag::note_enters_block_captures_weak, 259 diag::note_exits_block_captures_weak); 260 break; 261 case QualType::DK_none: 262 llvm_unreachable("non-lifetime captured variable"); 263 } 264 SourceLocation Loc = D->getLocation(); 265 if (Loc.isInvalid()) 266 Loc = BDecl->getLocation(); 267 Scopes.push_back(GotoScope(ParentScope, 268 Diags.first, Diags.second, Loc)); 269 ParentScope = Scopes.size()-1; 270 } 271} 272 273/// BuildScopeInformation - The statements from CI to CE are known to form a 274/// coherent VLA scope with a specified parent node. Walk through the 275/// statements, adding any labels or gotos to LabelAndGotoScopes and recursively 276/// walking the AST as needed. 277void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned &origParentScope) { 278 // If this is a statement, rather than an expression, scopes within it don't 279 // propagate out into the enclosing scope. Otherwise we have to worry 280 // about block literals, which have the lifetime of their enclosing statement. 281 unsigned independentParentScope = origParentScope; 282 unsigned &ParentScope = ((isa<Expr>(S) && !isa<StmtExpr>(S)) 283 ? origParentScope : independentParentScope); 284 285 bool SkipFirstSubStmt = false; 286 287 // If we found a label, remember that it is in ParentScope scope. 288 switch (S->getStmtClass()) { 289 case Stmt::AddrLabelExprClass: 290 IndirectJumpTargets.push_back(cast<AddrLabelExpr>(S)->getLabel()); 291 break; 292 293 case Stmt::IndirectGotoStmtClass: 294 // "goto *&&lbl;" is a special case which we treat as equivalent 295 // to a normal goto. In addition, we don't calculate scope in the 296 // operand (to avoid recording the address-of-label use), which 297 // works only because of the restricted set of expressions which 298 // we detect as constant targets. 299 if (cast<IndirectGotoStmt>(S)->getConstantTarget()) { 300 LabelAndGotoScopes[S] = ParentScope; 301 Jumps.push_back(S); 302 return; 303 } 304 305 LabelAndGotoScopes[S] = ParentScope; 306 IndirectJumps.push_back(cast<IndirectGotoStmt>(S)); 307 break; 308 309 case Stmt::SwitchStmtClass: 310 // Evaluate the condition variable before entering the scope of the switch 311 // statement. 312 if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) { 313 BuildScopeInformation(Var, ParentScope); 314 SkipFirstSubStmt = true; 315 } 316 // Fall through 317 318 case Stmt::GotoStmtClass: 319 // Remember both what scope a goto is in as well as the fact that we have 320 // it. This makes the second scan not have to walk the AST again. 321 LabelAndGotoScopes[S] = ParentScope; 322 Jumps.push_back(S); 323 break; 324 325 default: 326 break; 327 } 328 329 for (Stmt::child_range CI = S->children(); CI; ++CI) { 330 if (SkipFirstSubStmt) { 331 SkipFirstSubStmt = false; 332 continue; 333 } 334 335 Stmt *SubStmt = *CI; 336 if (SubStmt == 0) continue; 337 338 // Cases, labels, and defaults aren't "scope parents". It's also 339 // important to handle these iteratively instead of recursively in 340 // order to avoid blowing out the stack. 341 while (true) { 342 Stmt *Next; 343 if (CaseStmt *CS = dyn_cast<CaseStmt>(SubStmt)) 344 Next = CS->getSubStmt(); 345 else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SubStmt)) 346 Next = DS->getSubStmt(); 347 else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt)) 348 Next = LS->getSubStmt(); 349 else 350 break; 351 352 LabelAndGotoScopes[SubStmt] = ParentScope; 353 SubStmt = Next; 354 } 355 356 // If this is a declstmt with a VLA definition, it defines a scope from here 357 // to the end of the containing context. 358 if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) { 359 // The decl statement creates a scope if any of the decls in it are VLAs 360 // or have the cleanup attribute. 361 for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end(); 362 I != E; ++I) 363 BuildScopeInformation(*I, ParentScope); 364 continue; 365 } 366 // Disallow jumps into any part of an @try statement by pushing a scope and 367 // walking all sub-stmts in that scope. 368 if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) { 369 unsigned newParentScope; 370 // Recursively walk the AST for the @try part. 371 Scopes.push_back(GotoScope(ParentScope, 372 diag::note_protected_by_objc_try, 373 diag::note_exits_objc_try, 374 AT->getAtTryLoc())); 375 if (Stmt *TryPart = AT->getTryBody()) 376 BuildScopeInformation(TryPart, (newParentScope = Scopes.size()-1)); 377 378 // Jump from the catch to the finally or try is not valid. 379 for (unsigned I = 0, N = AT->getNumCatchStmts(); I != N; ++I) { 380 ObjCAtCatchStmt *AC = AT->getCatchStmt(I); 381 Scopes.push_back(GotoScope(ParentScope, 382 diag::note_protected_by_objc_catch, 383 diag::note_exits_objc_catch, 384 AC->getAtCatchLoc())); 385 // @catches are nested and it isn't 386 BuildScopeInformation(AC->getCatchBody(), 387 (newParentScope = Scopes.size()-1)); 388 } 389 390 // Jump from the finally to the try or catch is not valid. 391 if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) { 392 Scopes.push_back(GotoScope(ParentScope, 393 diag::note_protected_by_objc_finally, 394 diag::note_exits_objc_finally, 395 AF->getAtFinallyLoc())); 396 BuildScopeInformation(AF, (newParentScope = Scopes.size()-1)); 397 } 398 399 continue; 400 } 401 402 unsigned newParentScope; 403 // Disallow jumps into the protected statement of an @synchronized, but 404 // allow jumps into the object expression it protects. 405 if (ObjCAtSynchronizedStmt *AS = dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)){ 406 // Recursively walk the AST for the @synchronized object expr, it is 407 // evaluated in the normal scope. 408 BuildScopeInformation(AS->getSynchExpr(), ParentScope); 409 410 // Recursively walk the AST for the @synchronized part, protected by a new 411 // scope. 412 Scopes.push_back(GotoScope(ParentScope, 413 diag::note_protected_by_objc_synchronized, 414 diag::note_exits_objc_synchronized, 415 AS->getAtSynchronizedLoc())); 416 BuildScopeInformation(AS->getSynchBody(), 417 (newParentScope = Scopes.size()-1)); 418 continue; 419 } 420 421 // Disallow jumps into any part of a C++ try statement. This is pretty 422 // much the same as for Obj-C. 423 if (CXXTryStmt *TS = dyn_cast<CXXTryStmt>(SubStmt)) { 424 Scopes.push_back(GotoScope(ParentScope, 425 diag::note_protected_by_cxx_try, 426 diag::note_exits_cxx_try, 427 TS->getSourceRange().getBegin())); 428 if (Stmt *TryBlock = TS->getTryBlock()) 429 BuildScopeInformation(TryBlock, (newParentScope = Scopes.size()-1)); 430 431 // Jump from the catch into the try is not allowed either. 432 for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) { 433 CXXCatchStmt *CS = TS->getHandler(I); 434 Scopes.push_back(GotoScope(ParentScope, 435 diag::note_protected_by_cxx_catch, 436 diag::note_exits_cxx_catch, 437 CS->getSourceRange().getBegin())); 438 BuildScopeInformation(CS->getHandlerBlock(), 439 (newParentScope = Scopes.size()-1)); 440 } 441 442 continue; 443 } 444 445 // Disallow jumps into the protected statement of an @autoreleasepool. 446 if (ObjCAutoreleasePoolStmt *AS = dyn_cast<ObjCAutoreleasePoolStmt>(SubStmt)){ 447 // Recursively walk the AST for the @autoreleasepool part, protected by a new 448 // scope. 449 Scopes.push_back(GotoScope(ParentScope, 450 diag::note_protected_by_objc_autoreleasepool, 451 diag::note_exits_objc_autoreleasepool, 452 AS->getAtLoc())); 453 BuildScopeInformation(AS->getSubStmt(), (newParentScope = Scopes.size()-1)); 454 continue; 455 } 456 457 // Disallow jumps past full-expressions that use blocks with 458 // non-trivial cleanups of their captures. This is theoretically 459 // implementable but a lot of work which we haven't felt up to doing. 460 if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(SubStmt)) { 461 for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) { 462 const BlockDecl *BDecl = EWC->getObject(i); 463 for (BlockDecl::capture_const_iterator ci = BDecl->capture_begin(), 464 ce = BDecl->capture_end(); ci != ce; ++ci) { 465 VarDecl *variable = ci->getVariable(); 466 BuildScopeInformation(variable, BDecl, ParentScope); 467 } 468 } 469 } 470 471 // Recursively walk the AST. 472 BuildScopeInformation(SubStmt, ParentScope); 473 } 474} 475 476/// VerifyJumps - Verify each element of the Jumps array to see if they are 477/// valid, emitting diagnostics if not. 478void JumpScopeChecker::VerifyJumps() { 479 while (!Jumps.empty()) { 480 Stmt *Jump = Jumps.pop_back_val(); 481 482 // With a goto, 483 if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) { 484 CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(), 485 diag::err_goto_into_protected_scope, 486 diag::warn_goto_into_protected_scope, 487 diag::warn_cxx98_compat_goto_into_protected_scope); 488 continue; 489 } 490 491 // We only get indirect gotos here when they have a constant target. 492 if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Jump)) { 493 LabelDecl *Target = IGS->getConstantTarget(); 494 CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(), 495 diag::err_goto_into_protected_scope, 496 diag::warn_goto_into_protected_scope, 497 diag::warn_cxx98_compat_goto_into_protected_scope); 498 continue; 499 } 500 501 SwitchStmt *SS = cast<SwitchStmt>(Jump); 502 for (SwitchCase *SC = SS->getSwitchCaseList(); SC; 503 SC = SC->getNextSwitchCase()) { 504 assert(LabelAndGotoScopes.count(SC) && "Case not visited?"); 505 CheckJump(SS, SC, SC->getLocStart(), 506 diag::err_switch_into_protected_scope, 0, 507 diag::warn_cxx98_compat_switch_into_protected_scope); 508 } 509 } 510} 511 512/// VerifyIndirectJumps - Verify whether any possible indirect jump 513/// might cross a protection boundary. Unlike direct jumps, indirect 514/// jumps count cleanups as protection boundaries: since there's no 515/// way to know where the jump is going, we can't implicitly run the 516/// right cleanups the way we can with direct jumps. 517/// 518/// Thus, an indirect jump is "trivial" if it bypasses no 519/// initializations and no teardowns. More formally, an indirect jump 520/// from A to B is trivial if the path out from A to DCA(A,B) is 521/// trivial and the path in from DCA(A,B) to B is trivial, where 522/// DCA(A,B) is the deepest common ancestor of A and B. 523/// Jump-triviality is transitive but asymmetric. 524/// 525/// A path in is trivial if none of the entered scopes have an InDiag. 526/// A path out is trivial is none of the exited scopes have an OutDiag. 527/// 528/// Under these definitions, this function checks that the indirect 529/// jump between A and B is trivial for every indirect goto statement A 530/// and every label B whose address was taken in the function. 531void JumpScopeChecker::VerifyIndirectJumps() { 532 if (IndirectJumps.empty()) return; 533 534 // If there aren't any address-of-label expressions in this function, 535 // complain about the first indirect goto. 536 if (IndirectJumpTargets.empty()) { 537 S.Diag(IndirectJumps[0]->getGotoLoc(), 538 diag::err_indirect_goto_without_addrlabel); 539 return; 540 } 541 542 // Collect a single representative of every scope containing an 543 // indirect goto. For most code bases, this substantially cuts 544 // down on the number of jump sites we'll have to consider later. 545 typedef std::pair<unsigned, IndirectGotoStmt*> JumpScope; 546 SmallVector<JumpScope, 32> JumpScopes; 547 { 548 llvm::DenseMap<unsigned, IndirectGotoStmt*> JumpScopesMap; 549 for (SmallVectorImpl<IndirectGotoStmt*>::iterator 550 I = IndirectJumps.begin(), E = IndirectJumps.end(); I != E; ++I) { 551 IndirectGotoStmt *IG = *I; 552 assert(LabelAndGotoScopes.count(IG) && 553 "indirect jump didn't get added to scopes?"); 554 unsigned IGScope = LabelAndGotoScopes[IG]; 555 IndirectGotoStmt *&Entry = JumpScopesMap[IGScope]; 556 if (!Entry) Entry = IG; 557 } 558 JumpScopes.reserve(JumpScopesMap.size()); 559 for (llvm::DenseMap<unsigned, IndirectGotoStmt*>::iterator 560 I = JumpScopesMap.begin(), E = JumpScopesMap.end(); I != E; ++I) 561 JumpScopes.push_back(*I); 562 } 563 564 // Collect a single representative of every scope containing a 565 // label whose address was taken somewhere in the function. 566 // For most code bases, there will be only one such scope. 567 llvm::DenseMap<unsigned, LabelDecl*> TargetScopes; 568 for (SmallVectorImpl<LabelDecl*>::iterator 569 I = IndirectJumpTargets.begin(), E = IndirectJumpTargets.end(); 570 I != E; ++I) { 571 LabelDecl *TheLabel = *I; 572 assert(LabelAndGotoScopes.count(TheLabel->getStmt()) && 573 "Referenced label didn't get added to scopes?"); 574 unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()]; 575 LabelDecl *&Target = TargetScopes[LabelScope]; 576 if (!Target) Target = TheLabel; 577 } 578 579 // For each target scope, make sure it's trivially reachable from 580 // every scope containing a jump site. 581 // 582 // A path between scopes always consists of exitting zero or more 583 // scopes, then entering zero or more scopes. We build a set of 584 // of scopes S from which the target scope can be trivially 585 // entered, then verify that every jump scope can be trivially 586 // exitted to reach a scope in S. 587 llvm::BitVector Reachable(Scopes.size(), false); 588 for (llvm::DenseMap<unsigned,LabelDecl*>::iterator 589 TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) { 590 unsigned TargetScope = TI->first; 591 LabelDecl *TargetLabel = TI->second; 592 593 Reachable.reset(); 594 595 // Mark all the enclosing scopes from which you can safely jump 596 // into the target scope. 'Min' will end up being the index of 597 // the shallowest such scope. 598 unsigned Min = TargetScope; 599 while (true) { 600 Reachable.set(Min); 601 602 // Don't go beyond the outermost scope. 603 if (Min == 0) break; 604 605 // Stop if we can't trivially enter the current scope. 606 if (Scopes[Min].InDiag) break; 607 608 Min = Scopes[Min].ParentScope; 609 } 610 611 // Walk through all the jump sites, checking that they can trivially 612 // reach this label scope. 613 for (SmallVectorImpl<JumpScope>::iterator 614 I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) { 615 unsigned Scope = I->first; 616 617 // Walk out the "scope chain" for this scope, looking for a scope 618 // we've marked reachable. For well-formed code this amortizes 619 // to O(JumpScopes.size() / Scopes.size()): we only iterate 620 // when we see something unmarked, and in well-formed code we 621 // mark everything we iterate past. 622 bool IsReachable = false; 623 while (true) { 624 if (Reachable.test(Scope)) { 625 // If we find something reachable, mark all the scopes we just 626 // walked through as reachable. 627 for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope) 628 Reachable.set(S); 629 IsReachable = true; 630 break; 631 } 632 633 // Don't walk out if we've reached the top-level scope or we've 634 // gotten shallower than the shallowest reachable scope. 635 if (Scope == 0 || Scope < Min) break; 636 637 // Don't walk out through an out-diagnostic. 638 if (Scopes[Scope].OutDiag) break; 639 640 Scope = Scopes[Scope].ParentScope; 641 } 642 643 // Only diagnose if we didn't find something. 644 if (IsReachable) continue; 645 646 DiagnoseIndirectJump(I->second, I->first, TargetLabel, TargetScope); 647 } 648 } 649} 650 651/// Return true if a particular error+note combination must be downgraded to a 652/// warning in Microsoft mode. 653static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) { 654 return (JumpDiag == diag::err_goto_into_protected_scope && 655 (InDiagNote == diag::note_protected_by_variable_init || 656 InDiagNote == diag::note_protected_by_variable_nontriv_destructor)); 657} 658 659/// Return true if a particular note should be downgraded to a compatibility 660/// warning in C++11 mode. 661static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) { 662 return S.getLangOpts().CPlusPlus0x && 663 InDiagNote == diag::note_protected_by_variable_non_pod; 664} 665 666/// Produce primary diagnostic for an indirect jump statement. 667static void DiagnoseIndirectJumpStmt(Sema &S, IndirectGotoStmt *Jump, 668 LabelDecl *Target, bool &Diagnosed) { 669 if (Diagnosed) 670 return; 671 S.Diag(Jump->getGotoLoc(), diag::err_indirect_goto_in_protected_scope); 672 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target); 673 Diagnosed = true; 674} 675 676/// Produce note diagnostics for a jump into a protected scope. 677void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) { 678 assert(!ToScopes.empty()); 679 for (unsigned I = 0, E = ToScopes.size(); I != E; ++I) 680 if (Scopes[ToScopes[I]].InDiag) 681 S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag); 682} 683 684/// Diagnose an indirect jump which is known to cross scopes. 685void JumpScopeChecker::DiagnoseIndirectJump(IndirectGotoStmt *Jump, 686 unsigned JumpScope, 687 LabelDecl *Target, 688 unsigned TargetScope) { 689 assert(JumpScope != TargetScope); 690 691 unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope); 692 bool Diagnosed = false; 693 694 // Walk out the scope chain until we reach the common ancestor. 695 for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope) 696 if (Scopes[I].OutDiag) { 697 DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed); 698 S.Diag(Scopes[I].Loc, Scopes[I].OutDiag); 699 } 700 701 SmallVector<unsigned, 10> ToScopesCXX98Compat; 702 703 // Now walk into the scopes containing the label whose address was taken. 704 for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope) 705 if (IsCXX98CompatWarning(S, Scopes[I].InDiag)) 706 ToScopesCXX98Compat.push_back(I); 707 else if (Scopes[I].InDiag) { 708 DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed); 709 S.Diag(Scopes[I].Loc, Scopes[I].InDiag); 710 } 711 712 // Diagnose this jump if it would be ill-formed in C++98. 713 if (!Diagnosed && !ToScopesCXX98Compat.empty()) { 714 S.Diag(Jump->getGotoLoc(), 715 diag::warn_cxx98_compat_indirect_goto_in_protected_scope); 716 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target); 717 NoteJumpIntoScopes(ToScopesCXX98Compat); 718 } 719} 720 721/// CheckJump - Validate that the specified jump statement is valid: that it is 722/// jumping within or out of its current scope, not into a deeper one. 723void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc, 724 unsigned JumpDiagError, unsigned JumpDiagWarning, 725 unsigned JumpDiagCXX98Compat) { 726 assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?"); 727 unsigned FromScope = LabelAndGotoScopes[From]; 728 729 assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?"); 730 unsigned ToScope = LabelAndGotoScopes[To]; 731 732 // Common case: exactly the same scope, which is fine. 733 if (FromScope == ToScope) return; 734 735 unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope); 736 737 // It's okay to jump out from a nested scope. 738 if (CommonScope == ToScope) return; 739 740 // Pull out (and reverse) any scopes we might need to diagnose skipping. 741 SmallVector<unsigned, 10> ToScopesCXX98Compat; 742 SmallVector<unsigned, 10> ToScopesError; 743 SmallVector<unsigned, 10> ToScopesWarning; 744 for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) { 745 if (S.getLangOpts().MicrosoftMode && JumpDiagWarning != 0 && 746 IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag)) 747 ToScopesWarning.push_back(I); 748 else if (IsCXX98CompatWarning(S, Scopes[I].InDiag)) 749 ToScopesCXX98Compat.push_back(I); 750 else if (Scopes[I].InDiag) 751 ToScopesError.push_back(I); 752 } 753 754 // Handle warnings. 755 if (!ToScopesWarning.empty()) { 756 S.Diag(DiagLoc, JumpDiagWarning); 757 NoteJumpIntoScopes(ToScopesWarning); 758 } 759 760 // Handle errors. 761 if (!ToScopesError.empty()) { 762 S.Diag(DiagLoc, JumpDiagError); 763 NoteJumpIntoScopes(ToScopesError); 764 } 765 766 // Handle -Wc++98-compat warnings if the jump is well-formed. 767 if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) { 768 S.Diag(DiagLoc, JumpDiagCXX98Compat); 769 NoteJumpIntoScopes(ToScopesCXX98Compat); 770 } 771} 772 773void Sema::DiagnoseInvalidJumps(Stmt *Body) { 774 (void)JumpScopeChecker(Body, *this); 775} 776