clang  3.9.0
JumpDiagnostics.cpp
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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 
16 #include "clang/AST/DeclCXX.h"
17 #include "clang/AST/Expr.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/StmtCXX.h"
20 #include "clang/AST/StmtObjC.h"
21 #include "llvm/ADT/BitVector.h"
22 using namespace clang;
23 
24 namespace {
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 ///
32 class JumpScopeChecker {
33  Sema &S;
34 
35  /// Permissive - True when recovering from errors, in which case precautions
36  /// are taken to handle incomplete scope information.
37  const bool Permissive;
38 
39  /// GotoScope - This is a record that we use to keep track of all of the
40  /// scopes that are introduced by VLAs and other things that scope jumps like
41  /// gotos. This scope tree has nothing to do with the source scope tree,
42  /// because you can have multiple VLA scopes per compound statement, and most
43  /// compound statements don't introduce any scopes.
44  struct GotoScope {
45  /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
46  /// the parent scope is the function body.
47  unsigned ParentScope;
48 
49  /// InDiag - The note to emit if there is a jump into this scope.
50  unsigned InDiag;
51 
52  /// OutDiag - The note to emit if there is an indirect jump out
53  /// of this scope. Direct jumps always clean up their current scope
54  /// in an orderly way.
55  unsigned OutDiag;
56 
57  /// Loc - Location to emit the diagnostic.
58  SourceLocation Loc;
59 
60  GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag,
62  : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {}
63  };
64 
66  llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
68 
70  SmallVector<LabelDecl*, 4> IndirectJumpTargets;
71 public:
72  JumpScopeChecker(Stmt *Body, Sema &S);
73 private:
74  void BuildScopeInformation(Decl *D, unsigned &ParentScope);
75  void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,
76  unsigned &ParentScope);
77  void BuildScopeInformation(Stmt *S, unsigned &origParentScope);
78 
79  void VerifyJumps();
80  void VerifyIndirectJumps();
81  void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);
82  void DiagnoseIndirectJump(IndirectGotoStmt *IG, unsigned IGScope,
83  LabelDecl *Target, unsigned TargetScope);
84  void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
85  unsigned JumpDiag, unsigned JumpDiagWarning,
86  unsigned JumpDiagCXX98Compat);
87  void CheckGotoStmt(GotoStmt *GS);
88 
89  unsigned GetDeepestCommonScope(unsigned A, unsigned B);
90 };
91 } // end anonymous namespace
92 
93 #define CHECK_PERMISSIVE(x) (assert(Permissive || !(x)), (Permissive && (x)))
94 
95 JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s)
96  : S(s), Permissive(s.hasAnyUnrecoverableErrorsInThisFunction()) {
97  // Add a scope entry for function scope.
98  Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation()));
99 
100  // Build information for the top level compound statement, so that we have a
101  // defined scope record for every "goto" and label.
102  unsigned BodyParentScope = 0;
103  BuildScopeInformation(Body, BodyParentScope);
104 
105  // Check that all jumps we saw are kosher.
106  VerifyJumps();
107  VerifyIndirectJumps();
108 }
109 
110 /// GetDeepestCommonScope - Finds the innermost scope enclosing the
111 /// two scopes.
112 unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) {
113  while (A != B) {
114  // Inner scopes are created after outer scopes and therefore have
115  // higher indices.
116  if (A < B) {
117  assert(Scopes[B].ParentScope < B);
118  B = Scopes[B].ParentScope;
119  } else {
120  assert(Scopes[A].ParentScope < A);
121  A = Scopes[A].ParentScope;
122  }
123  }
124  return A;
125 }
126 
127 typedef std::pair<unsigned,unsigned> ScopePair;
128 
129 /// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
130 /// diagnostic that should be emitted if control goes over it. If not, return 0.
132  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
133  unsigned InDiag = 0;
134  unsigned OutDiag = 0;
135 
136  if (VD->getType()->isVariablyModifiedType())
137  InDiag = diag::note_protected_by_vla;
138 
139  if (VD->hasAttr<BlocksAttr>())
140  return ScopePair(diag::note_protected_by___block,
141  diag::note_exits___block);
142 
143  if (VD->hasAttr<CleanupAttr>())
144  return ScopePair(diag::note_protected_by_cleanup,
145  diag::note_exits_cleanup);
146 
147  if (VD->hasLocalStorage()) {
148  switch (VD->getType().isDestructedType()) {
149  case QualType::DK_objc_strong_lifetime:
150  return ScopePair(diag::note_protected_by_objc_strong_init,
151  diag::note_exits_objc_strong);
152 
153  case QualType::DK_objc_weak_lifetime:
154  return ScopePair(diag::note_protected_by_objc_weak_init,
155  diag::note_exits_objc_weak);
156 
157  case QualType::DK_cxx_destructor:
158  OutDiag = diag::note_exits_dtor;
159  break;
160 
161  case QualType::DK_none:
162  break;
163  }
164  }
165 
166  const Expr *Init = VD->getInit();
167  if (S.Context.getLangOpts().CPlusPlus && VD->hasLocalStorage() && Init) {
168  // C++11 [stmt.dcl]p3:
169  // A program that jumps from a point where a variable with automatic
170  // storage duration is not in scope to a point where it is in scope
171  // is ill-formed unless the variable has scalar type, class type with
172  // a trivial default constructor and a trivial destructor, a
173  // cv-qualified version of one of these types, or an array of one of
174  // the preceding types and is declared without an initializer.
175 
176  // C++03 [stmt.dcl.p3:
177  // A program that jumps from a point where a local variable
178  // with automatic storage duration is not in scope to a point
179  // where it is in scope is ill-formed unless the variable has
180  // POD type and is declared without an initializer.
181 
182  InDiag = diag::note_protected_by_variable_init;
183 
184  // For a variable of (array of) class type declared without an
185  // initializer, we will have call-style initialization and the initializer
186  // will be the CXXConstructExpr with no intervening nodes.
187  if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Init)) {
188  const CXXConstructorDecl *Ctor = CCE->getConstructor();
189  if (Ctor->isTrivial() && Ctor->isDefaultConstructor() &&
190  VD->getInitStyle() == VarDecl::CallInit) {
191  if (OutDiag)
192  InDiag = diag::note_protected_by_variable_nontriv_destructor;
193  else if (!Ctor->getParent()->isPOD())
194  InDiag = diag::note_protected_by_variable_non_pod;
195  else
196  InDiag = 0;
197  }
198  }
199  }
200 
201  return ScopePair(InDiag, OutDiag);
202  }
203 
204  if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {
205  if (TD->getUnderlyingType()->isVariablyModifiedType())
206  return ScopePair(isa<TypedefDecl>(TD)
207  ? diag::note_protected_by_vla_typedef
208  : diag::note_protected_by_vla_type_alias,
209  0);
210  }
211 
212  return ScopePair(0U, 0U);
213 }
214 
215 /// \brief Build scope information for a declaration that is part of a DeclStmt.
216 void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) {
217  // If this decl causes a new scope, push and switch to it.
218  std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S, D);
219  if (Diags.first || Diags.second) {
220  Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second,
221  D->getLocation()));
222  ParentScope = Scopes.size()-1;
223  }
224 
225  // If the decl has an initializer, walk it with the potentially new
226  // scope we just installed.
227  if (VarDecl *VD = dyn_cast<VarDecl>(D))
228  if (Expr *Init = VD->getInit())
229  BuildScopeInformation(Init, ParentScope);
230 }
231 
232 /// \brief Build scope information for a captured block literal variables.
233 void JumpScopeChecker::BuildScopeInformation(VarDecl *D,
234  const BlockDecl *BDecl,
235  unsigned &ParentScope) {
236  // exclude captured __block variables; there's no destructor
237  // associated with the block literal for them.
238  if (D->hasAttr<BlocksAttr>())
239  return;
240  QualType T = D->getType();
241  QualType::DestructionKind destructKind = T.isDestructedType();
242  if (destructKind != QualType::DK_none) {
243  std::pair<unsigned,unsigned> Diags;
244  switch (destructKind) {
245  case QualType::DK_cxx_destructor:
246  Diags = ScopePair(diag::note_enters_block_captures_cxx_obj,
247  diag::note_exits_block_captures_cxx_obj);
248  break;
249  case QualType::DK_objc_strong_lifetime:
250  Diags = ScopePair(diag::note_enters_block_captures_strong,
251  diag::note_exits_block_captures_strong);
252  break;
253  case QualType::DK_objc_weak_lifetime:
254  Diags = ScopePair(diag::note_enters_block_captures_weak,
255  diag::note_exits_block_captures_weak);
256  break;
257  case QualType::DK_none:
258  llvm_unreachable("non-lifetime captured variable");
259  }
260  SourceLocation Loc = D->getLocation();
261  if (Loc.isInvalid())
262  Loc = BDecl->getLocation();
263  Scopes.push_back(GotoScope(ParentScope,
264  Diags.first, Diags.second, Loc));
265  ParentScope = Scopes.size()-1;
266  }
267 }
268 
269 /// BuildScopeInformation - The statements from CI to CE are known to form a
270 /// coherent VLA scope with a specified parent node. Walk through the
271 /// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
272 /// walking the AST as needed.
273 void JumpScopeChecker::BuildScopeInformation(Stmt *S,
274  unsigned &origParentScope) {
275  // If this is a statement, rather than an expression, scopes within it don't
276  // propagate out into the enclosing scope. Otherwise we have to worry
277  // about block literals, which have the lifetime of their enclosing statement.
278  unsigned independentParentScope = origParentScope;
279  unsigned &ParentScope = ((isa<Expr>(S) && !isa<StmtExpr>(S))
280  ? origParentScope : independentParentScope);
281 
282  unsigned StmtsToSkip = 0u;
283 
284  // If we found a label, remember that it is in ParentScope scope.
285  switch (S->getStmtClass()) {
286  case Stmt::AddrLabelExprClass:
287  IndirectJumpTargets.push_back(cast<AddrLabelExpr>(S)->getLabel());
288  break;
289 
290  case Stmt::IndirectGotoStmtClass:
291  // "goto *&&lbl;" is a special case which we treat as equivalent
292  // to a normal goto. In addition, we don't calculate scope in the
293  // operand (to avoid recording the address-of-label use), which
294  // works only because of the restricted set of expressions which
295  // we detect as constant targets.
296  if (cast<IndirectGotoStmt>(S)->getConstantTarget()) {
297  LabelAndGotoScopes[S] = ParentScope;
298  Jumps.push_back(S);
299  return;
300  }
301 
302  LabelAndGotoScopes[S] = ParentScope;
303  IndirectJumps.push_back(cast<IndirectGotoStmt>(S));
304  break;
305 
306  case Stmt::SwitchStmtClass:
307  // Evaluate the C++17 init stmt and condition variable
308  // before entering the scope of the switch statement.
309  if (Stmt *Init = cast<SwitchStmt>(S)->getInit()) {
310  BuildScopeInformation(Init, ParentScope);
311  ++StmtsToSkip;
312  }
313  if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) {
314  BuildScopeInformation(Var, ParentScope);
315  ++StmtsToSkip;
316  }
317  // Fall through
318 
319  case Stmt::GotoStmtClass:
320  // Remember both what scope a goto is in as well as the fact that we have
321  // it. This makes the second scan not have to walk the AST again.
322  LabelAndGotoScopes[S] = ParentScope;
323  Jumps.push_back(S);
324  break;
325 
326  case Stmt::IfStmtClass: {
327  IfStmt *IS = cast<IfStmt>(S);
328  if (!IS->isConstexpr())
329  break;
330 
331  if (VarDecl *Var = IS->getConditionVariable())
332  BuildScopeInformation(Var, ParentScope);
333 
334  // Cannot jump into the middle of the condition.
335  unsigned NewParentScope = Scopes.size();
336  Scopes.push_back(GotoScope(ParentScope,
337  diag::note_protected_by_constexpr_if, 0,
338  IS->getLocStart()));
339  BuildScopeInformation(IS->getCond(), NewParentScope);
340 
341  // Jumps into either arm of an 'if constexpr' are not allowed.
342  NewParentScope = Scopes.size();
343  Scopes.push_back(GotoScope(ParentScope,
344  diag::note_protected_by_constexpr_if, 0,
345  IS->getLocStart()));
346  BuildScopeInformation(IS->getThen(), NewParentScope);
347  if (Stmt *Else = IS->getElse()) {
348  NewParentScope = Scopes.size();
349  Scopes.push_back(GotoScope(ParentScope,
350  diag::note_protected_by_constexpr_if, 0,
351  IS->getLocStart()));
352  BuildScopeInformation(Else, NewParentScope);
353  }
354  return;
355  }
356 
357  case Stmt::CXXTryStmtClass: {
358  CXXTryStmt *TS = cast<CXXTryStmt>(S);
359  {
360  unsigned NewParentScope = Scopes.size();
361  Scopes.push_back(GotoScope(ParentScope,
362  diag::note_protected_by_cxx_try,
363  diag::note_exits_cxx_try,
364  TS->getSourceRange().getBegin()));
365  if (Stmt *TryBlock = TS->getTryBlock())
366  BuildScopeInformation(TryBlock, NewParentScope);
367  }
368 
369  // Jump from the catch into the try is not allowed either.
370  for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
371  CXXCatchStmt *CS = TS->getHandler(I);
372  unsigned NewParentScope = Scopes.size();
373  Scopes.push_back(GotoScope(ParentScope,
374  diag::note_protected_by_cxx_catch,
375  diag::note_exits_cxx_catch,
376  CS->getSourceRange().getBegin()));
377  BuildScopeInformation(CS->getHandlerBlock(), NewParentScope);
378  }
379  return;
380  }
381 
382  case Stmt::SEHTryStmtClass: {
383  SEHTryStmt *TS = cast<SEHTryStmt>(S);
384  {
385  unsigned NewParentScope = Scopes.size();
386  Scopes.push_back(GotoScope(ParentScope,
387  diag::note_protected_by_seh_try,
388  diag::note_exits_seh_try,
389  TS->getSourceRange().getBegin()));
390  if (Stmt *TryBlock = TS->getTryBlock())
391  BuildScopeInformation(TryBlock, NewParentScope);
392  }
393 
394  // Jump from __except or __finally into the __try are not allowed either.
395  if (SEHExceptStmt *Except = TS->getExceptHandler()) {
396  unsigned NewParentScope = Scopes.size();
397  Scopes.push_back(GotoScope(ParentScope,
398  diag::note_protected_by_seh_except,
399  diag::note_exits_seh_except,
400  Except->getSourceRange().getBegin()));
401  BuildScopeInformation(Except->getBlock(), NewParentScope);
402  } else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) {
403  unsigned NewParentScope = Scopes.size();
404  Scopes.push_back(GotoScope(ParentScope,
405  diag::note_protected_by_seh_finally,
406  diag::note_exits_seh_finally,
407  Finally->getSourceRange().getBegin()));
408  BuildScopeInformation(Finally->getBlock(), NewParentScope);
409  }
410 
411  return;
412  }
413 
414  case Stmt::DeclStmtClass: {
415  // If this is a declstmt with a VLA definition, it defines a scope from here
416  // to the end of the containing context.
417  DeclStmt *DS = cast<DeclStmt>(S);
418  // The decl statement creates a scope if any of the decls in it are VLAs
419  // or have the cleanup attribute.
420  for (auto *I : DS->decls())
421  BuildScopeInformation(I, origParentScope);
422  return;
423  }
424 
425  case Stmt::ObjCAtTryStmtClass: {
426  // Disallow jumps into any part of an @try statement by pushing a scope and
427  // walking all sub-stmts in that scope.
428  ObjCAtTryStmt *AT = cast<ObjCAtTryStmt>(S);
429  // Recursively walk the AST for the @try part.
430  {
431  unsigned NewParentScope = Scopes.size();
432  Scopes.push_back(GotoScope(ParentScope,
433  diag::note_protected_by_objc_try,
434  diag::note_exits_objc_try,
435  AT->getAtTryLoc()));
436  if (Stmt *TryPart = AT->getTryBody())
437  BuildScopeInformation(TryPart, NewParentScope);
438  }
439 
440  // Jump from the catch to the finally or try is not valid.
441  for (unsigned I = 0, N = AT->getNumCatchStmts(); I != N; ++I) {
442  ObjCAtCatchStmt *AC = AT->getCatchStmt(I);
443  unsigned NewParentScope = Scopes.size();
444  Scopes.push_back(GotoScope(ParentScope,
445  diag::note_protected_by_objc_catch,
446  diag::note_exits_objc_catch,
447  AC->getAtCatchLoc()));
448  // @catches are nested and it isn't
449  BuildScopeInformation(AC->getCatchBody(), NewParentScope);
450  }
451 
452  // Jump from the finally to the try or catch is not valid.
453  if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
454  unsigned NewParentScope = Scopes.size();
455  Scopes.push_back(GotoScope(ParentScope,
456  diag::note_protected_by_objc_finally,
457  diag::note_exits_objc_finally,
458  AF->getAtFinallyLoc()));
459  BuildScopeInformation(AF, NewParentScope);
460  }
461 
462  return;
463  }
464 
465  case Stmt::ObjCAtSynchronizedStmtClass: {
466  // Disallow jumps into the protected statement of an @synchronized, but
467  // allow jumps into the object expression it protects.
468  ObjCAtSynchronizedStmt *AS = cast<ObjCAtSynchronizedStmt>(S);
469  // Recursively walk the AST for the @synchronized object expr, it is
470  // evaluated in the normal scope.
471  BuildScopeInformation(AS->getSynchExpr(), ParentScope);
472 
473  // Recursively walk the AST for the @synchronized part, protected by a new
474  // scope.
475  unsigned NewParentScope = Scopes.size();
476  Scopes.push_back(GotoScope(ParentScope,
477  diag::note_protected_by_objc_synchronized,
478  diag::note_exits_objc_synchronized,
479  AS->getAtSynchronizedLoc()));
480  BuildScopeInformation(AS->getSynchBody(), NewParentScope);
481  return;
482  }
483 
484  case Stmt::ObjCAutoreleasePoolStmtClass: {
485  // Disallow jumps into the protected statement of an @autoreleasepool.
486  ObjCAutoreleasePoolStmt *AS = cast<ObjCAutoreleasePoolStmt>(S);
487  // Recursively walk the AST for the @autoreleasepool part, protected by a
488  // new scope.
489  unsigned NewParentScope = Scopes.size();
490  Scopes.push_back(GotoScope(ParentScope,
491  diag::note_protected_by_objc_autoreleasepool,
492  diag::note_exits_objc_autoreleasepool,
493  AS->getAtLoc()));
494  BuildScopeInformation(AS->getSubStmt(), NewParentScope);
495  return;
496  }
497 
498  case Stmt::ExprWithCleanupsClass: {
499  // Disallow jumps past full-expressions that use blocks with
500  // non-trivial cleanups of their captures. This is theoretically
501  // implementable but a lot of work which we haven't felt up to doing.
502  ExprWithCleanups *EWC = cast<ExprWithCleanups>(S);
503  for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) {
504  const BlockDecl *BDecl = EWC->getObject(i);
505  for (const auto &CI : BDecl->captures()) {
506  VarDecl *variable = CI.getVariable();
507  BuildScopeInformation(variable, BDecl, origParentScope);
508  }
509  }
510  break;
511  }
512 
513  case Stmt::MaterializeTemporaryExprClass: {
514  // Disallow jumps out of scopes containing temporaries lifetime-extended to
515  // automatic storage duration.
516  MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(S);
517  if (MTE->getStorageDuration() == SD_Automatic) {
520  const Expr *ExtendedObject =
522  CommaLHS, Adjustments);
523  if (ExtendedObject->getType().isDestructedType()) {
524  Scopes.push_back(GotoScope(ParentScope, 0,
525  diag::note_exits_temporary_dtor,
526  ExtendedObject->getExprLoc()));
527  origParentScope = Scopes.size()-1;
528  }
529  }
530  break;
531  }
532 
533  case Stmt::CaseStmtClass:
534  case Stmt::DefaultStmtClass:
535  case Stmt::LabelStmtClass:
536  LabelAndGotoScopes[S] = ParentScope;
537  break;
538 
539  default:
540  break;
541  }
542 
543  for (Stmt *SubStmt : S->children()) {
544  if (!SubStmt)
545  continue;
546  if (StmtsToSkip) {
547  --StmtsToSkip;
548  continue;
549  }
550 
551  // Cases, labels, and defaults aren't "scope parents". It's also
552  // important to handle these iteratively instead of recursively in
553  // order to avoid blowing out the stack.
554  while (true) {
555  Stmt *Next;
556  if (CaseStmt *CS = dyn_cast<CaseStmt>(SubStmt))
557  Next = CS->getSubStmt();
558  else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SubStmt))
559  Next = DS->getSubStmt();
560  else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt))
561  Next = LS->getSubStmt();
562  else
563  break;
564 
565  LabelAndGotoScopes[SubStmt] = ParentScope;
566  SubStmt = Next;
567  }
568 
569  // Recursively walk the AST.
570  BuildScopeInformation(SubStmt, ParentScope);
571  }
572 }
573 
574 /// VerifyJumps - Verify each element of the Jumps array to see if they are
575 /// valid, emitting diagnostics if not.
576 void JumpScopeChecker::VerifyJumps() {
577  while (!Jumps.empty()) {
578  Stmt *Jump = Jumps.pop_back_val();
579 
580  // With a goto,
581  if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {
582  // The label may not have a statement if it's coming from inline MS ASM.
583  if (GS->getLabel()->getStmt()) {
584  CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),
585  diag::err_goto_into_protected_scope,
586  diag::ext_goto_into_protected_scope,
587  diag::warn_cxx98_compat_goto_into_protected_scope);
588  }
589  CheckGotoStmt(GS);
590  continue;
591  }
592 
593  // We only get indirect gotos here when they have a constant target.
594  if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Jump)) {
595  LabelDecl *Target = IGS->getConstantTarget();
596  CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(),
597  diag::err_goto_into_protected_scope,
598  diag::ext_goto_into_protected_scope,
599  diag::warn_cxx98_compat_goto_into_protected_scope);
600  continue;
601  }
602 
603  SwitchStmt *SS = cast<SwitchStmt>(Jump);
604  for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
605  SC = SC->getNextSwitchCase()) {
606  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC)))
607  continue;
608  SourceLocation Loc;
609  if (CaseStmt *CS = dyn_cast<CaseStmt>(SC))
610  Loc = CS->getLocStart();
611  else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC))
612  Loc = DS->getLocStart();
613  else
614  Loc = SC->getLocStart();
615  CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,
616  diag::warn_cxx98_compat_switch_into_protected_scope);
617  }
618  }
619 }
620 
621 /// VerifyIndirectJumps - Verify whether any possible indirect jump
622 /// might cross a protection boundary. Unlike direct jumps, indirect
623 /// jumps count cleanups as protection boundaries: since there's no
624 /// way to know where the jump is going, we can't implicitly run the
625 /// right cleanups the way we can with direct jumps.
626 ///
627 /// Thus, an indirect jump is "trivial" if it bypasses no
628 /// initializations and no teardowns. More formally, an indirect jump
629 /// from A to B is trivial if the path out from A to DCA(A,B) is
630 /// trivial and the path in from DCA(A,B) to B is trivial, where
631 /// DCA(A,B) is the deepest common ancestor of A and B.
632 /// Jump-triviality is transitive but asymmetric.
633 ///
634 /// A path in is trivial if none of the entered scopes have an InDiag.
635 /// A path out is trivial is none of the exited scopes have an OutDiag.
636 ///
637 /// Under these definitions, this function checks that the indirect
638 /// jump between A and B is trivial for every indirect goto statement A
639 /// and every label B whose address was taken in the function.
640 void JumpScopeChecker::VerifyIndirectJumps() {
641  if (IndirectJumps.empty()) return;
642 
643  // If there aren't any address-of-label expressions in this function,
644  // complain about the first indirect goto.
645  if (IndirectJumpTargets.empty()) {
646  S.Diag(IndirectJumps[0]->getGotoLoc(),
647  diag::err_indirect_goto_without_addrlabel);
648  return;
649  }
650 
651  // Collect a single representative of every scope containing an
652  // indirect goto. For most code bases, this substantially cuts
653  // down on the number of jump sites we'll have to consider later.
654  typedef std::pair<unsigned, IndirectGotoStmt*> JumpScope;
655  SmallVector<JumpScope, 32> JumpScopes;
656  {
657  llvm::DenseMap<unsigned, IndirectGotoStmt*> JumpScopesMap;
659  I = IndirectJumps.begin(), E = IndirectJumps.end(); I != E; ++I) {
660  IndirectGotoStmt *IG = *I;
661  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG)))
662  continue;
663  unsigned IGScope = LabelAndGotoScopes[IG];
664  IndirectGotoStmt *&Entry = JumpScopesMap[IGScope];
665  if (!Entry) Entry = IG;
666  }
667  JumpScopes.reserve(JumpScopesMap.size());
669  I = JumpScopesMap.begin(), E = JumpScopesMap.end(); I != E; ++I)
670  JumpScopes.push_back(*I);
671  }
672 
673  // Collect a single representative of every scope containing a
674  // label whose address was taken somewhere in the function.
675  // For most code bases, there will be only one such scope.
676  llvm::DenseMap<unsigned, LabelDecl*> TargetScopes;
678  I = IndirectJumpTargets.begin(), E = IndirectJumpTargets.end();
679  I != E; ++I) {
680  LabelDecl *TheLabel = *I;
681  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt())))
682  continue;
683  unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()];
684  LabelDecl *&Target = TargetScopes[LabelScope];
685  if (!Target) Target = TheLabel;
686  }
687 
688  // For each target scope, make sure it's trivially reachable from
689  // every scope containing a jump site.
690  //
691  // A path between scopes always consists of exitting zero or more
692  // scopes, then entering zero or more scopes. We build a set of
693  // of scopes S from which the target scope can be trivially
694  // entered, then verify that every jump scope can be trivially
695  // exitted to reach a scope in S.
696  llvm::BitVector Reachable(Scopes.size(), false);
698  TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) {
699  unsigned TargetScope = TI->first;
700  LabelDecl *TargetLabel = TI->second;
701 
702  Reachable.reset();
703 
704  // Mark all the enclosing scopes from which you can safely jump
705  // into the target scope. 'Min' will end up being the index of
706  // the shallowest such scope.
707  unsigned Min = TargetScope;
708  while (true) {
709  Reachable.set(Min);
710 
711  // Don't go beyond the outermost scope.
712  if (Min == 0) break;
713 
714  // Stop if we can't trivially enter the current scope.
715  if (Scopes[Min].InDiag) break;
716 
717  Min = Scopes[Min].ParentScope;
718  }
719 
720  // Walk through all the jump sites, checking that they can trivially
721  // reach this label scope.
723  I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) {
724  unsigned Scope = I->first;
725 
726  // Walk out the "scope chain" for this scope, looking for a scope
727  // we've marked reachable. For well-formed code this amortizes
728  // to O(JumpScopes.size() / Scopes.size()): we only iterate
729  // when we see something unmarked, and in well-formed code we
730  // mark everything we iterate past.
731  bool IsReachable = false;
732  while (true) {
733  if (Reachable.test(Scope)) {
734  // If we find something reachable, mark all the scopes we just
735  // walked through as reachable.
736  for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope)
737  Reachable.set(S);
738  IsReachable = true;
739  break;
740  }
741 
742  // Don't walk out if we've reached the top-level scope or we've
743  // gotten shallower than the shallowest reachable scope.
744  if (Scope == 0 || Scope < Min) break;
745 
746  // Don't walk out through an out-diagnostic.
747  if (Scopes[Scope].OutDiag) break;
748 
749  Scope = Scopes[Scope].ParentScope;
750  }
751 
752  // Only diagnose if we didn't find something.
753  if (IsReachable) continue;
754 
755  DiagnoseIndirectJump(I->second, I->first, TargetLabel, TargetScope);
756  }
757  }
758 }
759 
760 /// Return true if a particular error+note combination must be downgraded to a
761 /// warning in Microsoft mode.
762 static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) {
763  return (JumpDiag == diag::err_goto_into_protected_scope &&
764  (InDiagNote == diag::note_protected_by_variable_init ||
765  InDiagNote == diag::note_protected_by_variable_nontriv_destructor));
766 }
767 
768 /// Return true if a particular note should be downgraded to a compatibility
769 /// warning in C++11 mode.
770 static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) {
771  return S.getLangOpts().CPlusPlus11 &&
772  InDiagNote == diag::note_protected_by_variable_non_pod;
773 }
774 
775 /// Produce primary diagnostic for an indirect jump statement.
777  LabelDecl *Target, bool &Diagnosed) {
778  if (Diagnosed)
779  return;
780  S.Diag(Jump->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
781  S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);
782  Diagnosed = true;
783 }
784 
785 /// Produce note diagnostics for a jump into a protected scope.
786 void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {
787  if (CHECK_PERMISSIVE(ToScopes.empty()))
788  return;
789  for (unsigned I = 0, E = ToScopes.size(); I != E; ++I)
790  if (Scopes[ToScopes[I]].InDiag)
791  S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag);
792 }
793 
794 /// Diagnose an indirect jump which is known to cross scopes.
795 void JumpScopeChecker::DiagnoseIndirectJump(IndirectGotoStmt *Jump,
796  unsigned JumpScope,
797  LabelDecl *Target,
798  unsigned TargetScope) {
799  if (CHECK_PERMISSIVE(JumpScope == TargetScope))
800  return;
801 
802  unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope);
803  bool Diagnosed = false;
804 
805  // Walk out the scope chain until we reach the common ancestor.
806  for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope)
807  if (Scopes[I].OutDiag) {
808  DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);
809  S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);
810  }
811 
812  SmallVector<unsigned, 10> ToScopesCXX98Compat;
813 
814  // Now walk into the scopes containing the label whose address was taken.
815  for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope)
816  if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
817  ToScopesCXX98Compat.push_back(I);
818  else if (Scopes[I].InDiag) {
819  DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);
820  S.Diag(Scopes[I].Loc, Scopes[I].InDiag);
821  }
822 
823  // Diagnose this jump if it would be ill-formed in C++98.
824  if (!Diagnosed && !ToScopesCXX98Compat.empty()) {
825  S.Diag(Jump->getGotoLoc(),
826  diag::warn_cxx98_compat_indirect_goto_in_protected_scope);
827  S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);
828  NoteJumpIntoScopes(ToScopesCXX98Compat);
829  }
830 }
831 
832 /// CheckJump - Validate that the specified jump statement is valid: that it is
833 /// jumping within or out of its current scope, not into a deeper one.
834 void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
835  unsigned JumpDiagError, unsigned JumpDiagWarning,
836  unsigned JumpDiagCXX98Compat) {
837  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(From)))
838  return;
839  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To)))
840  return;
841 
842  unsigned FromScope = LabelAndGotoScopes[From];
843  unsigned ToScope = LabelAndGotoScopes[To];
844 
845  // Common case: exactly the same scope, which is fine.
846  if (FromScope == ToScope) return;
847 
848  // Warn on gotos out of __finally blocks.
849  if (isa<GotoStmt>(From) || isa<IndirectGotoStmt>(From)) {
850  // If FromScope > ToScope, FromScope is more nested and the jump goes to a
851  // less nested scope. Check if it crosses a __finally along the way.
852  for (unsigned I = FromScope; I > ToScope; I = Scopes[I].ParentScope) {
853  if (Scopes[I].InDiag == diag::note_protected_by_seh_finally) {
854  S.Diag(From->getLocStart(), diag::warn_jump_out_of_seh_finally);
855  break;
856  }
857  }
858  }
859 
860  unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope);
861 
862  // It's okay to jump out from a nested scope.
863  if (CommonScope == ToScope) return;
864 
865  // Pull out (and reverse) any scopes we might need to diagnose skipping.
866  SmallVector<unsigned, 10> ToScopesCXX98Compat;
867  SmallVector<unsigned, 10> ToScopesError;
868  SmallVector<unsigned, 10> ToScopesWarning;
869  for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) {
870  if (S.getLangOpts().MSVCCompat && JumpDiagWarning != 0 &&
871  IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag))
872  ToScopesWarning.push_back(I);
873  else if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
874  ToScopesCXX98Compat.push_back(I);
875  else if (Scopes[I].InDiag)
876  ToScopesError.push_back(I);
877  }
878 
879  // Handle warnings.
880  if (!ToScopesWarning.empty()) {
881  S.Diag(DiagLoc, JumpDiagWarning);
882  NoteJumpIntoScopes(ToScopesWarning);
883  }
884 
885  // Handle errors.
886  if (!ToScopesError.empty()) {
887  S.Diag(DiagLoc, JumpDiagError);
888  NoteJumpIntoScopes(ToScopesError);
889  }
890 
891  // Handle -Wc++98-compat warnings if the jump is well-formed.
892  if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) {
893  S.Diag(DiagLoc, JumpDiagCXX98Compat);
894  NoteJumpIntoScopes(ToScopesCXX98Compat);
895  }
896 }
897 
898 void JumpScopeChecker::CheckGotoStmt(GotoStmt *GS) {
899  if (GS->getLabel()->isMSAsmLabel()) {
900  S.Diag(GS->getGotoLoc(), diag::err_goto_ms_asm_label)
901  << GS->getLabel()->getIdentifier();
902  S.Diag(GS->getLabel()->getLocation(), diag::note_goto_ms_asm_label)
903  << GS->getLabel()->getIdentifier();
904  }
905 }
906 
907 void Sema::DiagnoseInvalidJumps(Stmt *Body) {
908  (void)JumpScopeChecker(Body, *this);
909 }
const SwitchCase * getNextSwitchCase() const
Definition: Stmt.h:664
const ObjCAtFinallyStmt * getFinallyStmt() const
Retrieve the @finally statement, if any.
Definition: StmtObjC.h:224
A (possibly-)qualified type.
Definition: Type.h:598
ArrayRef< Capture > captures() const
Definition: Decl.h:3581
DestructionKind isDestructedType() const
Returns a nonzero value if objects of this type require non-trivial work to clean up after...
Definition: Type.h:1032
IdentifierInfo * getIdentifier() const
getIdentifier - Get the identifier that names this declaration, if there is one.
Definition: Decl.h:232
const LangOptions & getLangOpts() const
Definition: Sema.h:1062
CXXCatchStmt * getHandler(unsigned i)
Definition: StmtCXX.h:104
IfStmt - This represents an if/then/else.
Definition: Stmt.h:881
Expr * GetTemporaryExpr() const
Retrieve the temporary-generating subexpression whose value will be materialized into a glvalue...
Definition: ExprCXX.h:4003
static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote)
Return true if a particular error+note combination must be downgraded to a warning in Microsoft mode...
SemaDiagnosticBuilder Diag(SourceLocation Loc, unsigned DiagID)
Emit a diagnostic.
Definition: Sema.h:1139
Represents a call to a C++ constructor.
Definition: ExprCXX.h:1162
const Stmt * getElse() const
Definition: Stmt.h:921
Represents a C++ constructor within a class.
Definition: DeclCXX.h:2187
Represents a prvalue temporary that is written into memory so that a reference can bind to it...
Definition: ExprCXX.h:3962
VarDecl - An instance of this class is created to represent a variable declaration or definition...
Definition: Decl.h:768
SourceLocation getLocStart() const LLVM_READONLY
Definition: StmtCXX.h:44
#define CHECK_PERMISSIVE(x)
Defines the Objective-C statement AST node classes.
Represents an expression – generally a full-expression – that introduces cleanups to be run at the en...
Definition: ExprCXX.h:2936
Defines the clang::Expr interface and subclasses for C++ expressions.
LabelStmt - Represents a label, which has a substatement.
Definition: Stmt.h:789
Represents Objective-C's @catch statement.
Definition: StmtObjC.h:74
const CompoundStmt * getSynchBody() const
Definition: StmtObjC.h:282
IndirectGotoStmt - This represents an indirect goto.
Definition: Stmt.h:1258
const LangOptions & getLangOpts() const
Definition: ASTContext.h:604
const CXXRecordDecl * getParent() const
Returns the parent of this method declaration, which is the class in which this method is defined...
Definition: DeclCXX.h:1838
Stmt * getHandlerBlock() const
Definition: StmtCXX.h:52
const Expr * skipRValueSubobjectAdjustments(SmallVectorImpl< const Expr * > &CommaLHS, SmallVectorImpl< SubobjectAdjustment > &Adjustments) const
Walk outwards from an expression we want to bind a reference to and find the expression whose lifetim...
Definition: Expr.cpp:54
LabelStmt * getStmt() const
Definition: Decl.h:449
Scope - A scope is a transient data structure that is used while parsing the program.
Definition: Scope.h:39
const Stmt * getCatchBody() const
Definition: StmtObjC.h:90
const ObjCAtCatchStmt * getCatchStmt(unsigned I) const
Retrieve a @catch statement.
Definition: StmtObjC.h:206
CleanupObject getObject(unsigned i) const
Definition: ExprCXX.h:2971
detail::InMemoryDirectory::const_iterator I
QualType getType() const
Definition: Decl.h:599
bool isInvalid() const
Sema - This implements semantic analysis and AST building for C.
Definition: Sema.h:263
SourceLocation getLocStart() const LLVM_READONLY
Definition: Stmt.h:936
unsigned getNumObjects() const
Definition: ExprCXX.h:2969
BlockDecl - This represents a block literal declaration, which is like an unnamed FunctionDecl...
Definition: Decl.h:3456
Expr - This represents one expression.
Definition: Expr.h:105
StorageDuration getStorageDuration() const
Retrieve the storage duration for the materialized temporary.
Definition: ExprCXX.h:4006
SourceLocation getGotoLoc() const
Definition: Stmt.h:1238
Represents Objective-C's @synchronized statement.
Definition: StmtObjC.h:262
CXXTryStmt - A C++ try block, including all handlers.
Definition: StmtCXX.h:65
bool isMSAsmLabel() const
Definition: Decl.h:459
const SwitchCase * getSwitchCaseList() const
Definition: Stmt.h:996
std::pair< unsigned, unsigned > ScopePair
SourceLocation getAtLoc() const
Definition: StmtObjC.h:363
LabelDecl * getLabel() const
Definition: Stmt.h:1235
SourceLocation getGotoLoc() const
Definition: Stmt.h:1273
SmallVectorImpl< AnnotatedLine * >::const_iterator Next
Encodes a location in the source.
bool isConstexpr() const
Definition: Stmt.h:933
const TemplateArgument * iterator
Definition: Type.h:4233
DeclStmt - Adaptor class for mixing declarations with statements and expressions. ...
Definition: Stmt.h:443
LabelDecl - Represents the declaration of a label.
Definition: Decl.h:424
SourceLocation getIdentLoc() const
Definition: Stmt.h:805
SEHExceptStmt * getExceptHandler() const
Returns 0 if not defined.
Definition: Stmt.cpp:924
SourceLocation getAtSynchronizedLoc() const
Definition: StmtObjC.h:279
SourceLocation getExprLoc() const LLVM_READONLY
getExprLoc - Return the preferred location for the arrow when diagnosing a problem with a generic exp...
Definition: Expr.cpp:193
Base class for declarations which introduce a typedef-name.
Definition: Decl.h:2609
QualType getType() const
Definition: Expr.h:126
VarDecl * getConditionVariable() const
Retrieve the variable declared in this "if" statement, if any.
Definition: Stmt.cpp:778
SourceLocation getLocStart() const LLVM_READONLY
Definition: Stmt.h:473
const Expr * getSynchExpr() const
Definition: StmtObjC.h:290
unsigned getNumHandlers() const
Definition: StmtCXX.h:103
detail::InMemoryDirectory::const_iterator E
const Stmt * getThen() const
Definition: Stmt.h:919
SwitchStmt - This represents a 'switch' stmt.
Definition: Stmt.h:957
SourceLocation getAtCatchLoc() const
Definition: StmtObjC.h:102
const Stmt * getSubStmt() const
Definition: StmtObjC.h:356
SourceLocation getAtTryLoc() const
Retrieve the location of the @ in the @try.
Definition: StmtObjC.h:193
decl_range decls()
Definition: Stmt.h:491
bool isTrivial() const
Whether this function is "trivial" in some specialized C++ senses.
Definition: Decl.h:1848
Represents Objective-C's @finally statement.
Definition: StmtObjC.h:120
unsigned getNumCatchStmts() const
Retrieve the number of @catch statements in this try-catch-finally block.
Definition: StmtObjC.h:203
bool isDefaultConstructor() const
Whether this constructor is a default constructor (C++ [class.ctor]p5), which can be used to default-...
Definition: DeclCXX.cpp:1863
GotoStmt - This represents a direct goto.
Definition: Stmt.h:1224
static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D)
GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a diagnostic that should be e...
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
static void DiagnoseIndirectJumpStmt(Sema &S, IndirectGotoStmt *Jump, LabelDecl *Target, bool &Diagnosed)
Produce primary diagnostic for an indirect jump statement.
CXXCatchStmt - This represents a C++ catch block.
Definition: StmtCXX.h:29
const Expr * getCond() const
Definition: Stmt.h:917
CompoundStmt * getTryBlock()
Definition: StmtCXX.h:96
Represents Objective-C's @try ... @catch ... @finally statement.
Definition: StmtObjC.h:154
const Stmt * getTryBody() const
Retrieve the @try body.
Definition: StmtObjC.h:197
ASTContext & Context
Definition: Sema.h:299
CompoundStmt * getTryBlock() const
Definition: Stmt.h:1951
Automatic storage duration (most local variables).
Definition: Specifiers.h:271
Represents Objective-C's @autoreleasepool Statement.
Definition: StmtObjC.h:345
SEHFinallyStmt * getFinallyHandler() const
Definition: Stmt.cpp:928
static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote)
Return true if a particular note should be downgraded to a compatibility warning in C++11 mode...
bool isPOD() const
Whether this class is a POD-type (C++ [class]p4)
Definition: DeclCXX.h:1135