//===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- C++ -*-=//

//

//                     The LLVM Compiler Infrastructure

//

// This file is distributed under the University of Illinois Open Source

// License. See LICENSE.TXT for details.

//

//===----------------------------------------------------------------------===//

//

// This file implements the JumpScopeChecker class, which is used to diagnose

// jumps that enter a protected scope in an invalid way.

//

//===----------------------------------------------------------------------===//

#include "clang/Sema/SemaInternal.h"

#include "clang/AST/DeclCXX.h"

#include "clang/AST/Expr.h"

#include "clang/AST/ExprCXX.h"

#include "clang/AST/StmtCXX.h"

#include "clang/AST/StmtObjC.h"

#include "llvm/ADT/BitVector.h"

using namespace clang;

namespace {

/// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps

/// into VLA and other protected scopes.  For example, this rejects:

///    goto L;

///    int a[n];

///  L:

///

class JumpScopeChecker {

  Sema &S;

  /// Permissive - True when recovering from errors, in which case precautions

  /// are taken to handle incomplete scope information.

  const bool Permissive;

  /// GotoScope - This is a record that we use to keep track of all of the

  /// scopes that are introduced by VLAs and other things that scope jumps like

  /// gotos.  This scope tree has nothing to do with the source scope tree,

  /// because you can have multiple VLA scopes per compound statement, and most

  /// compound statements don't introduce any scopes.

  struct GotoScope {

    /// ParentScope - The index in ScopeMap of the parent scope.  This is 0 for

    /// the parent scope is the function body.

    unsigned ParentScope;

    /// InDiag - The note to emit if there is a jump into this scope.

    unsigned InDiag;

    /// OutDiag - The note to emit if there is an indirect jump out

    /// of this scope.  Direct jumps always clean up their current scope

    /// in an orderly way.

    unsigned OutDiag;

    /// Loc - Location to emit the diagnostic.

    SourceLocation Loc;

    GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag,

              SourceLocation L)

      : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {}

  };

  SmallVector<GotoScope, 48> Scopes;

  llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;

  SmallVector<Stmt*, 16> Jumps;

  SmallVector<IndirectGotoStmt*, 4> IndirectJumps;

  SmallVector<LabelDecl*, 4> IndirectJumpTargets;

public:

  JumpScopeChecker(Stmt *Body, Sema &S);

private:

  void BuildScopeInformation(Decl *D, unsigned &ParentScope);

  void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,

                             unsigned &ParentScope);

  void BuildScopeInformation(Stmt *S, unsigned &origParentScope);

  void VerifyJumps();

  void VerifyIndirectJumps();

  void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);

  void DiagnoseIndirectJump(IndirectGotoStmt *IG, unsigned IGScope,

                            LabelDecl *Target, unsigned TargetScope);

  void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,

                 unsigned JumpDiag, unsigned JumpDiagWarning,

                 unsigned JumpDiagCXX98Compat);

  void CheckGotoStmt(GotoStmt *GS);

  unsigned GetDeepestCommonScope(unsigned A, unsigned B);

};

} // end anonymous namespace

#define CHECK_PERMISSIVE(x) (assert(Permissive || !(x)), (Permissive && 
(x)192
))

JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s)

    : S(s), Permissive(s.hasAnyUnrecoverableErrorsInThisFunction()) {

  // Add a scope entry for function scope.

  Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation()));

  // Build information for the top level compound statement, so that we have a

  // defined scope record for every "goto" and label.

  unsigned BodyParentScope = 0;

  BuildScopeInformation(Body, BodyParentScope);

  // Check that all jumps we saw are kosher.

  VerifyJumps();

  VerifyIndirectJumps();

}

/// GetDeepestCommonScope - Finds the innermost scope enclosing the

/// two scopes.

unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) {

  while (A != B) {

    // Inner scopes are created after outer scopes and therefore have

    // higher indices.

    if (A < B) {

      assert(Scopes[B].ParentScope < B);

      B = Scopes[B].ParentScope;

    } else {

      assert(Scopes[A].ParentScope < A);

      A = Scopes[A].ParentScope;

    }

  }

  return A;

}

typedef std::pair<unsigned,unsigned> ScopePair;

/// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a

/// diagnostic that should be emitted if control goes over it. If not, return 0.

static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D) {

  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {

    unsigned InDiag = 0;

    unsigned OutDiag = 0;

    if (VD->getType()->isVariablyModifiedType())

      InDiag = diag::note_protected_by_vla;

    if (VD->hasAttr<BlocksAttr>())

      return ScopePair(diag::note_protected_by___block,

                       diag::note_exits___block);

    if (VD->hasAttr<CleanupAttr>())

      return ScopePair(diag::note_protected_by_cleanup,

                       diag::note_exits_cleanup);

    if (VD->hasLocalStorage()) {

      switch (VD->getType().isDestructedType()) {

      case QualType::DK_objc_strong_lifetime:

      case QualType::DK_objc_weak_lifetime:

        return ScopePair(diag::note_protected_by_objc_ownership,

                         diag::note_exits_objc_ownership);

      case QualType::DK_cxx_destructor:

        OutDiag = diag::note_exits_dtor;

        break;

      case QualType::DK_none:

        break;

      }

    }

    const Expr *Init = VD->getInit();

    if (S.Context.getLangOpts().CPlusPlus && VD->hasLocalStorage() && 
Init1.26k
) {

      // C++11 [stmt.dcl]p3:

      //   A program that jumps from a point where a variable with automatic

      //   storage duration is not in scope to a point where it is in scope

      //   is ill-formed unless the variable has scalar type, class type with

      //   a trivial default constructor and a trivial destructor, a

      //   cv-qualified version of one of these types, or an array of one of

      //   the preceding types and is declared without an initializer.

      // C++03 [stmt.dcl.p3:

      //   A program that jumps from a point where a local variable

      //   with automatic storage duration is not in scope to a point

      //   where it is in scope is ill-formed unless the variable has

      //   POD type and is declared without an initializer.

      InDiag = diag::note_protected_by_variable_init;

      // For a variable of (array of) class type declared without an

      // initializer, we will have call-style initialization and the initializer

      // will be the CXXConstructExpr with no intervening nodes.

      if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Init)) {

        const CXXConstructorDecl *Ctor = CCE->getConstructor();

        if (Ctor->isTrivial() && 
Ctor->isDefaultConstructor()0
 &&

            
VD->getInitStyle() == VarDecl::CallInit0
) {

          if (OutDiag)

            InDiag = diag::note_protected_by_variable_nontriv_destructor;

          else if (!Ctor->getParent()->isPOD())

            InDiag = diag::note_protected_by_variable_non_pod;

          else

            InDiag = 0;

        }

      }

    }

    return ScopePair(InDiag, OutDiag);

  }

  if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {

    if (TD->getUnderlyingType()->isVariablyModifiedType())

      return ScopePair(isa<TypedefDecl>(TD)

                           ? diag::note_protected_by_vla_typedef

                           : diag::note_protected_by_vla_type_alias,

                       0);

  }

  return ScopePair(0U, 0U);

}

/// \brief Build scope information for a declaration that is part of a DeclStmt.

void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) {

  // If this decl causes a new scope, push and switch to it.

  std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S, D);

  if (Diags.first || 
Diags.second296
) {

    Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second,

                               D->getLocation()));

    ParentScope = Scopes.size()-1;

  }

  // If the decl has an initializer, walk it with the potentially new

  // scope we just installed.

  if (VarDecl *VD = dyn_cast<VarDecl>(D))

    if (Expr *Init = VD->getInit())

      BuildScopeInformation(Init, ParentScope);

}

/// \brief Build scope information for a captured block literal variables.

void JumpScopeChecker::BuildScopeInformation(VarDecl *D,

                                             const BlockDecl *BDecl,

                                             unsigned &ParentScope) {

  // exclude captured __block variables; there's no destructor

  // associated with the block literal for them.

  if (D->hasAttr<BlocksAttr>())

    return;

  QualType T = D->getType();

  QualType::DestructionKind destructKind = T.isDestructedType();

  if (destructKind != QualType::DK_none) {

    std::pair<unsigned,unsigned> Diags;

    switch (destructKind) {

      case QualType::DK_cxx_destructor:

        Diags = ScopePair(diag::note_enters_block_captures_cxx_obj,

                          diag::note_exits_block_captures_cxx_obj);

        break;

      case QualType::DK_objc_strong_lifetime:

        Diags = ScopePair(diag::note_enters_block_captures_strong,

                          diag::note_exits_block_captures_strong);

        break;

      case QualType::DK_objc_weak_lifetime:

        Diags = ScopePair(diag::note_enters_block_captures_weak,

                          diag::note_exits_block_captures_weak);

        break;

      case QualType::DK_none:

        llvm_unreachable("non-lifetime captured variable");

    }

    SourceLocation Loc = D->getLocation();

    if (Loc.isInvalid())

      Loc = BDecl->getLocation();

    Scopes.push_back(GotoScope(ParentScope,

                               Diags.first, Diags.second, Loc));

    ParentScope = Scopes.size()-1;

  }

}

/// BuildScopeInformation - The statements from CI to CE are known to form a

/// coherent VLA scope with a specified parent node.  Walk through the

/// statements, adding any labels or gotos to LabelAndGotoScopes and recursively

/// walking the AST as needed.

void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned &origParentScope) {

  // If this is a statement, rather than an expression, scopes within it don't

  // propagate out into the enclosing scope.  Otherwise we have to worry

  // about block literals, which have the lifetime of their enclosing statement.

  unsigned independentParentScope = origParentScope;

  unsigned &ParentScope = ((isa<Expr>(S) && 
!isa<StmtExpr>(S)69.4k
)

                            ? 
origParentScope69.4k
 : 
independentParentScope5.83k
);

  bool SkipFirstSubStmt = false;

  // If we found a label, remember that it is in ParentScope scope.

  switch (S->getStmtClass()) {

  case Stmt::AddrLabelExprClass:

    IndirectJumpTargets.push_back(cast<AddrLabelExpr>(S)->getLabel());

    break;

  case Stmt::IndirectGotoStmtClass:

    // "goto *&&lbl;" is a special case which we treat as equivalent

    // to a normal goto.  In addition, we don't calculate scope in the

    // operand (to avoid recording the address-of-label use), which

    // works only because of the restricted set of expressions which

    // we detect as constant targets.

    if (cast<IndirectGotoStmt>(S)->getConstantTarget()) {

      LabelAndGotoScopes[S] = ParentScope;

      Jumps.push_back(S);

      return;

    }

    LabelAndGotoScopes[S] = ParentScope;

    IndirectJumps.push_back(cast<IndirectGotoStmt>(S));

    break;

  case Stmt::SwitchStmtClass:

    // Evaluate the condition variable before entering the scope of the switch

    // statement.

    if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) {

      BuildScopeInformation(Var, ParentScope);

      SkipFirstSubStmt = true;

    }

    LLVM_FALLTHROUGH; // HLSL Change

  case Stmt::GotoStmtClass:

    // Remember both what scope a goto is in as well as the fact that we have

    // it.  This makes the second scan not have to walk the AST again.

    LabelAndGotoScopes[S] = ParentScope;

    Jumps.push_back(S);

    break;

  case Stmt::CXXTryStmtClass: {

    CXXTryStmt *TS = cast<CXXTryStmt>(S);

    unsigned newParentScope;

    Scopes.push_back(GotoScope(ParentScope,

                               diag::note_protected_by_cxx_try,

                               diag::note_exits_cxx_try,

                               TS->getSourceRange().getBegin()));

    if (Stmt *TryBlock = TS->getTryBlock())

      BuildScopeInformation(TryBlock, (newParentScope = Scopes.size()-1));

    // Jump from the catch into the try is not allowed either.

    for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {

      CXXCatchStmt *CS = TS->getHandler(I);

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_cxx_catch,

                                 diag::note_exits_cxx_catch,

                                 CS->getSourceRange().getBegin()));

      BuildScopeInformation(CS->getHandlerBlock(),

                            (newParentScope = Scopes.size()-1));

    }

    return;

  }

  case Stmt::SEHTryStmtClass: {

    SEHTryStmt *TS = cast<SEHTryStmt>(S);

    unsigned newParentScope;

    Scopes.push_back(GotoScope(ParentScope,

                               diag::note_protected_by_seh_try,

                               diag::note_exits_seh_try,

                               TS->getSourceRange().getBegin()));

    if (Stmt *TryBlock = TS->getTryBlock())

      BuildScopeInformation(TryBlock, (newParentScope = Scopes.size()-1));

    // Jump from __except or __finally into the __try are not allowed either.

    if (SEHExceptStmt *Except = TS->getExceptHandler()) {

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_seh_except,

                                 diag::note_exits_seh_except,

                                 Except->getSourceRange().getBegin()));

      BuildScopeInformation(Except->getBlock(),

                            (newParentScope = Scopes.size()-1));

    } else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) {

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_seh_finally,

                                 diag::note_exits_seh_finally,

                                 Finally->getSourceRange().getBegin()));

      BuildScopeInformation(Finally->getBlock(),

                            (newParentScope = Scopes.size()-1));

    }

    return;

  }

  default:

    break;

  }

  
for (Stmt *SubStmt : S->children())75.2k
 {

    if (SkipFirstSubStmt) {

      SkipFirstSubStmt = false;

      continue;

    }

    if (!SubStmt) 
continue2.23k
;

    // Cases, labels, and defaults aren't "scope parents".  It's also

    // important to handle these iteratively instead of recursively in

    // order to avoid blowing out the stack.

    
while (75.1k
true) {

      Stmt *Next;

      if (CaseStmt *CS = dyn_cast<CaseStmt>(SubStmt))

        Next = CS->getSubStmt();

      else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SubStmt))

        Next = DS->getSubStmt();

      else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt))

        Next = LS->getSubStmt();

      else

        break;

      LabelAndGotoScopes[SubStmt] = ParentScope;

      SubStmt = Next;

    }

    // If this is a declstmt with a VLA definition, it defines a scope from here

    // to the end of the containing context.

    if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) {

      // The decl statement creates a scope if any of the decls in it are VLAs

      // or have the cleanup attribute.

      for (auto *I : DS->decls())

        BuildScopeInformation(I, ParentScope);

      continue;

    }

    // Disallow jumps into any part of an @try statement by pushing a scope and

    // walking all sub-stmts in that scope.

    if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) {

      unsigned newParentScope;

      // Recursively walk the AST for the @try part.

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_objc_try,

                                 diag::note_exits_objc_try,

                                 AT->getAtTryLoc()));

      if (Stmt *TryPart = AT->getTryBody())

        BuildScopeInformation(TryPart, (newParentScope = Scopes.size()-1));

      // Jump from the catch to the finally or try is not valid.

      for (unsigned I = 0, N = AT->getNumCatchStmts(); I != N; ++I) {

        ObjCAtCatchStmt *AC = AT->getCatchStmt(I);

        Scopes.push_back(GotoScope(ParentScope,

                                   diag::note_protected_by_objc_catch,

                                   diag::note_exits_objc_catch,

                                   AC->getAtCatchLoc()));

        // @catches are nested and it isn't

        BuildScopeInformation(AC->getCatchBody(),

                              (newParentScope = Scopes.size()-1));

      }

      // Jump from the finally to the try or catch is not valid.

      if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {

        Scopes.push_back(GotoScope(ParentScope,

                                   diag::note_protected_by_objc_finally,

                                   diag::note_exits_objc_finally,

                                   AF->getAtFinallyLoc()));

        BuildScopeInformation(AF, (newParentScope = Scopes.size()-1));

      }

      continue;

    }

    unsigned newParentScope;

    // Disallow jumps into the protected statement of an @synchronized, but

    // allow jumps into the object expression it protects.

    if (ObjCAtSynchronizedStmt *AS =

            dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)) {

      // Recursively walk the AST for the @synchronized object expr, it is

      // evaluated in the normal scope.

      BuildScopeInformation(AS->getSynchExpr(), ParentScope);

      // Recursively walk the AST for the @synchronized part, protected by a new

      // scope.

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_objc_synchronized,

                                 diag::note_exits_objc_synchronized,

                                 AS->getAtSynchronizedLoc()));

      BuildScopeInformation(AS->getSynchBody(),

                            (newParentScope = Scopes.size()-1));

      continue;

    }

    // Disallow jumps into the protected statement of an @autoreleasepool.

    if (ObjCAutoreleasePoolStmt *AS =

            dyn_cast<ObjCAutoreleasePoolStmt>(SubStmt)) {

      // Recursively walk the AST for the @autoreleasepool part, protected by a

      // new scope.

      Scopes.push_back(GotoScope(ParentScope,

                                 diag::note_protected_by_objc_autoreleasepool,

                                 diag::note_exits_objc_autoreleasepool,

                                 AS->getAtLoc()));

      BuildScopeInformation(AS->getSubStmt(),

                            (newParentScope = Scopes.size() - 1));

      continue;

    }

    // Disallow jumps past full-expressions that use blocks with

    // non-trivial cleanups of their captures.  This is theoretically

    // implementable but a lot of work which we haven't felt up to doing.

    if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(SubStmt)) {

      for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) {

        const BlockDecl *BDecl = EWC->getObject(i);

        for (const auto &CI : BDecl->captures()) {

          VarDecl *variable = CI.getVariable();

          BuildScopeInformation(variable, BDecl, ParentScope);

        }

      }

    }

    // Disallow jumps out of scopes containing temporaries lifetime-extended to

    // automatic storage duration.

    if (MaterializeTemporaryExpr *MTE =

            dyn_cast<MaterializeTemporaryExpr>(SubStmt)) {

      if (MTE->getStorageDuration() == SD_Automatic) {

        SmallVector<const Expr *, 4> CommaLHS;

        SmallVector<SubobjectAdjustment, 4> Adjustments;

        const Expr *ExtendedObject =

            MTE->GetTemporaryExpr()->skipRValueSubobjectAdjustments(

                CommaLHS, Adjustments);

        if (ExtendedObject->getType().isDestructedType()) {

          Scopes.push_back(GotoScope(ParentScope, 0,

                                     diag::note_exits_temporary_dtor,

                                     ExtendedObject->getExprLoc()));

          ParentScope = Scopes.size()-1;

        }

      }

    }

    // Recursively walk the AST.

    BuildScopeInformation(SubStmt, ParentScope);

  }

}

/// VerifyJumps - Verify each element of the Jumps array to see if they are

/// valid, emitting diagnostics if not.

void JumpScopeChecker::VerifyJumps() {

  while (!Jumps.empty()) {

    Stmt *Jump = Jumps.pop_back_val();

    // With a goto,

    if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {

      // The label may not have a statement if it's coming from inline MS ASM.

      if (GS->getLabel()->getStmt()) {

        CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),

                  diag::err_goto_into_protected_scope,

                  diag::ext_goto_into_protected_scope,

                  diag::warn_cxx98_compat_goto_into_protected_scope);

      }

      CheckGotoStmt(GS);

      continue;

    }

    // We only get indirect gotos here when they have a constant target.

    if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Jump)) {

      LabelDecl *Target = IGS->getConstantTarget();

      CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(),

                diag::err_goto_into_protected_scope,

                diag::ext_goto_into_protected_scope,

                diag::warn_cxx98_compat_goto_into_protected_scope);

      continue;

    }

    SwitchStmt *SS = cast<SwitchStmt>(Jump);

    for (SwitchCase *SC = SS->getSwitchCaseList(); SC;

         SC = SC->getNextSwitchCase()) {

      if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC)))

        continue;

      SourceLocation Loc;

      if (CaseStmt *CS = dyn_cast<CaseStmt>(SC))

        Loc = CS->getLocStart();

      else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC))

        Loc = DS->getLocStart();

      else

        Loc = SC->getLocStart();

      CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,

                diag::warn_cxx98_compat_switch_into_protected_scope);

    }

  }

}

/// VerifyIndirectJumps - Verify whether any possible indirect jump

/// might cross a protection boundary.  Unlike direct jumps, indirect

/// jumps count cleanups as protection boundaries:  since there's no

/// way to know where the jump is going, we can't implicitly run the

/// right cleanups the way we can with direct jumps.

///

/// Thus, an indirect jump is "trivial" if it bypasses no

/// initializations and no teardowns.  More formally, an indirect jump

/// from A to B is trivial if the path out from A to DCA(A,B) is

/// trivial and the path in from DCA(A,B) to B is trivial, where

/// DCA(A,B) is the deepest common ancestor of A and B.

/// Jump-triviality is transitive but asymmetric.

///

/// A path in is trivial if none of the entered scopes have an InDiag.

/// A path out is trivial is none of the exited scopes have an OutDiag.

///

/// Under these definitions, this function checks that the indirect

/// jump between A and B is trivial for every indirect goto statement A

/// and every label B whose address was taken in the function.

void JumpScopeChecker::VerifyIndirectJumps() {

  if (IndirectJumps.empty()) return;

  // If there aren't any address-of-label expressions in this function,

  // complain about the first indirect goto.

  if (IndirectJumpTargets.empty()) {

    S.Diag(IndirectJumps[0]->getGotoLoc(),

           diag::err_indirect_goto_without_addrlabel);

    return;

  }

  // Collect a single representative of every scope containing an

  // indirect goto.  For most code bases, this substantially cuts

  // down on the number of jump sites we'll have to consider later.

  typedef std::pair<unsigned, IndirectGotoStmt*> JumpScope;

  SmallVector<JumpScope, 32> JumpScopes;

  {

    llvm::DenseMap<unsigned, IndirectGotoStmt*> JumpScopesMap;

    for (SmallVectorImpl<IndirectGotoStmt*>::iterator

           I = IndirectJumps.begin(), E = IndirectJumps.end(); I != E; ++I) {

      IndirectGotoStmt *IG = *I;

      if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG)))

        continue;

      unsigned IGScope = LabelAndGotoScopes[IG];

      IndirectGotoStmt *&Entry = JumpScopesMap[IGScope];

      if (!Entry) Entry = IG;

    }

    JumpScopes.reserve(JumpScopesMap.size());

    for (llvm::DenseMap<unsigned, IndirectGotoStmt*>::iterator

           I = JumpScopesMap.begin(), E = JumpScopesMap.end(); I != E; ++I)

      JumpScopes.push_back(*I);

  }

  // Collect a single representative of every scope containing a

  // label whose address was taken somewhere in the function.

  // For most code bases, there will be only one such scope.

  llvm::DenseMap<unsigned, LabelDecl*> TargetScopes;

  for (SmallVectorImpl<LabelDecl*>::iterator

         I = IndirectJumpTargets.begin(), E = IndirectJumpTargets.end();

       I != E; ++I) {

    LabelDecl *TheLabel = *I;

    if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt())))

      continue;

    unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()];

    LabelDecl *&Target = TargetScopes[LabelScope];

    if (!Target) Target = TheLabel;

  }

  // For each target scope, make sure it's trivially reachable from

  // every scope containing a jump site.

  //

  // A path between scopes always consists of exitting zero or more

  // scopes, then entering zero or more scopes.  We build a set of

  // of scopes S from which the target scope can be trivially

  // entered, then verify that every jump scope can be trivially

  // exitted to reach a scope in S.

  llvm::BitVector Reachable(Scopes.size(), false);

  for (llvm::DenseMap<unsigned,LabelDecl*>::iterator

         TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) {

    unsigned TargetScope = TI->first;

    LabelDecl *TargetLabel = TI->second;

    Reachable.reset();

    // Mark all the enclosing scopes from which you can safely jump

    // into the target scope.  'Min' will end up being the index of

    // the shallowest such scope.

    unsigned Min = TargetScope;

    while (true) {

      Reachable.set(Min);

      // Don't go beyond the outermost scope.

      if (Min == 0) break;

      // Stop if we can't trivially enter the current scope.

      if (Scopes[Min].InDiag) break;

      Min = Scopes[Min].ParentScope;

    }

    // Walk through all the jump sites, checking that they can trivially

    // reach this label scope.

    for (SmallVectorImpl<JumpScope>::iterator

           I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) {

      unsigned Scope = I->first;

      // Walk out the "scope chain" for this scope, looking for a scope

      // we've marked reachable.  For well-formed code this amortizes

      // to O(JumpScopes.size() / Scopes.size()):  we only iterate

      // when we see something unmarked, and in well-formed code we

      // mark everything we iterate past.

      bool IsReachable = false;

      while (true) {

        if (Reachable.test(Scope)) {

          // If we find something reachable, mark all the scopes we just

          // walked through as reachable.

          for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope)

            Reachable.set(S);

          IsReachable = true;

          break;

        }

        // Don't walk out if we've reached the top-level scope or we've

        // gotten shallower than the shallowest reachable scope.

        if (Scope == 0 || Scope < Min) break;

        // Don't walk out through an out-diagnostic.

        if (Scopes[Scope].OutDiag) break;

        Scope = Scopes[Scope].ParentScope;

      }

      // Only diagnose if we didn't find something.

      if (IsReachable) continue;

      DiagnoseIndirectJump(I->second, I->first, TargetLabel, TargetScope);

    }

  }

}

/// Return true if a particular error+note combination must be downgraded to a

/// warning in Microsoft mode.

static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) {

  return (JumpDiag == diag::err_goto_into_protected_scope &&

         (InDiagNote == diag::note_protected_by_variable_init ||

          InDiagNote == diag::note_protected_by_variable_nontriv_destructor));

}

/// Return true if a particular note should be downgraded to a compatibility

/// warning in C++11 mode.

static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) {

  return S.getLangOpts().CPlusPlus11 &&

         InDiagNote == diag::note_protected_by_variable_non_pod;

}

/// Produce primary diagnostic for an indirect jump statement.

static void DiagnoseIndirectJumpStmt(Sema &S, IndirectGotoStmt *Jump,

                                     LabelDecl *Target, bool &Diagnosed) {

  if (Diagnosed)

    return;

  S.Diag(Jump->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);

  S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);

  Diagnosed = true;

}

/// Produce note diagnostics for a jump into a protected scope.

void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {

  if (CHECK_PERMISSIVE(ToScopes.empty()))

    return;

  for (unsigned I = 0, E = ToScopes.size(); I != E; ++I)

    if (Scopes[ToScopes[I]].InDiag)

      S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag);

}

/// Diagnose an indirect jump which is known to cross scopes.

void JumpScopeChecker::DiagnoseIndirectJump(IndirectGotoStmt *Jump,

                                            unsigned JumpScope,

                                            LabelDecl *Target,

                                            unsigned TargetScope) {

  if (CHECK_PERMISSIVE(JumpScope == TargetScope))

    return;

  unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope);

  bool Diagnosed = false;

  // Walk out the scope chain until we reach the common ancestor.

  for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope)

    if (Scopes[I].OutDiag) {

      DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);

      S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);

    }

  SmallVector<unsigned, 10> ToScopesCXX98Compat;

  // Now walk into the scopes containing the label whose address was taken.

  for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope)

    if (IsCXX98CompatWarning(S, Scopes[I].InDiag))

      ToScopesCXX98Compat.push_back(I);

    else if (Scopes[I].InDiag) {

      DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);

      S.Diag(Scopes[I].Loc, Scopes[I].InDiag);

    }

  // Diagnose this jump if it would be ill-formed in C++98.

  if (!Diagnosed && !ToScopesCXX98Compat.empty()) {

    S.Diag(Jump->getGotoLoc(),

           diag::warn_cxx98_compat_indirect_goto_in_protected_scope);

    S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);

    NoteJumpIntoScopes(ToScopesCXX98Compat);

  }

}

/// CheckJump - Validate that the specified jump statement is valid: that it is

/// jumping within or out of its current scope, not into a deeper one.

void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,

                               unsigned JumpDiagError, unsigned JumpDiagWarning,

                                 unsigned JumpDiagCXX98Compat) {

  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(From)))

    return;

  if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To)))

    return;

  unsigned FromScope = LabelAndGotoScopes[From];

  unsigned ToScope = LabelAndGotoScopes[To];

  // Common case: exactly the same scope, which is fine.

  if (FromScope == ToScope) return;

  // Warn on gotos out of __finally blocks.

  if (isa<GotoStmt>(From) || isa<IndirectGotoStmt>(From)) {

    // If FromScope > ToScope, FromScope is more nested and the jump goes to a

    // less nested scope.  Check if it crosses a __finally along the way.

    for (unsigned I = FromScope; I > ToScope; I = Scopes[I].ParentScope) {

      if (Scopes[I].InDiag == diag::note_protected_by_seh_finally) {

        S.Diag(From->getLocStart(), diag::warn_jump_out_of_seh_finally);

        break;

      }

    }

  }

  unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope);

  // It's okay to jump out from a nested scope.

  if (CommonScope == ToScope) return;

  // Pull out (and reverse) any scopes we might need to diagnose skipping.

  SmallVector<unsigned, 10> ToScopesCXX98Compat;

  SmallVector<unsigned, 10> ToScopesError;

  SmallVector<unsigned, 10> ToScopesWarning;

  for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) {

    if (S.getLangOpts().MSVCCompat && JumpDiagWarning != 0 &&

        IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag))

      ToScopesWarning.push_back(I);

    else if (IsCXX98CompatWarning(S, Scopes[I].InDiag))

      ToScopesCXX98Compat.push_back(I);

    else if (Scopes[I].InDiag)

      ToScopesError.push_back(I);

  }

  // Handle warnings.

  if (!ToScopesWarning.empty()) {

    S.Diag(DiagLoc, JumpDiagWarning);

    NoteJumpIntoScopes(ToScopesWarning);

  }

  // Handle errors.

  if (!ToScopesError.empty()) {

    S.Diag(DiagLoc, JumpDiagError);

    NoteJumpIntoScopes(ToScopesError);

  }

  // Handle -Wc++98-compat warnings if the jump is well-formed.

  if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) {

    S.Diag(DiagLoc, JumpDiagCXX98Compat);

    NoteJumpIntoScopes(ToScopesCXX98Compat);

  }

}

void JumpScopeChecker::CheckGotoStmt(GotoStmt *GS) {

  if (GS->getLabel()->isMSAsmLabel()) {

    S.Diag(GS->getGotoLoc(), diag::err_goto_ms_asm_label)

        << GS->getLabel()->getIdentifier();

    S.Diag(GS->getLabel()->getLocation(), diag::note_goto_ms_asm_label)

        << GS->getLabel()->getIdentifier();

  }

}

void Sema::DiagnoseInvalidJumps(Stmt *Body) {

  (void)JumpScopeChecker(Body, *this);

}