Add the clang library to the repo (with some of my changes, too).

1 files changed, 770 insertions, 0 deletions

diff --git a/clang/lib/Sema/JumpDiagnostics.cpp b/clang/lib/Sema/JumpDiagnostics.cpp
new file mode 100644
index 0000000..ab786c6
--- /dev/null
+++ b/clang/lib/Sema/JumpDiagnostics.cpp
@@ -0,0 +1,770 @@
+//===--- 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/StmtObjC.h"
+#include "clang/AST/StmtCXX.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;
+
+  /// 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);
+
+  unsigned GetDeepestCommonScope(unsigned A, unsigned B);
+};
+} // end anonymous namespace
+
+
+JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
+  // 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(ASTContext &Context, const Decl *D) {
+  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
+    unsigned InDiag = 0, 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 (Context.getLangOpts().ObjCAutoRefCount && VD->hasLocalStorage()) {
+      switch (VD->getType().getObjCLifetime()) {
+      case Qualifiers::OCL_None:
+      case Qualifiers::OCL_ExplicitNone:
+      case Qualifiers::OCL_Autoreleasing:
+        break;
+
+      case Qualifiers::OCL_Strong:
+      case Qualifiers::OCL_Weak:
+        return ScopePair(diag::note_protected_by_objc_ownership,
+                         diag::note_exits_objc_ownership);
+      }
+    }
+
+    if (Context.getLangOpts().CPlusPlus && VD->hasLocalStorage()) {
+      // 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.
+
+      if (const Expr *init = VD->getInit()) {
+        // We actually give variables of record type (or array thereof)
+        // an initializer even if that initializer only calls a trivial
+        // ctor.  Detect that case.
+        // FIXME: With generalized initializer lists, this may
+        // classify "X x{};" as having no initializer.
+        unsigned inDiagToUse = diag::note_protected_by_variable_init;
+
+        const CXXRecordDecl *record = 0;
+
+        if (const CXXConstructExpr *cce = dyn_cast<CXXConstructExpr>(init)) {
+          const CXXConstructorDecl *ctor = cce->getConstructor();
+          record = ctor->getParent();
+
+          if (ctor->isTrivial() && ctor->isDefaultConstructor()) {
+            if (!record->hasTrivialDestructor())
+              inDiagToUse = diag::note_protected_by_variable_nontriv_destructor;
+            else if (!record->isPOD())
+              inDiagToUse = diag::note_protected_by_variable_non_pod;
+            else
+              inDiagToUse = 0;
+          }
+        } else if (VD->getType()->isArrayType()) {
+          record = VD->getType()->getBaseElementTypeUnsafe()
+                                ->getAsCXXRecordDecl();
+        }
+
+        if (inDiagToUse)
+          InDiag = inDiagToUse;
+
+        // Also object to indirect jumps which leave scopes with dtors.
+        if (record && !record->hasTrivialDestructor())
+          OutDiag = diag::note_exits_dtor;
+      }
+    }
+    
+    return ScopePair(InDiag, OutDiag);    
+  }
+
+  if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
+    if (TD->getUnderlyingType()->isVariablyModifiedType())
+      return ScopePair(diag::note_protected_by_vla_typedef, 0);
+  }
+
+  if (const TypeAliasDecl *TD = dyn_cast<TypeAliasDecl>(D)) {
+    if (TD->getUnderlyingType()->isVariablyModifiedType())
+      return ScopePair(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.Context, D);
+  if (Diags.first || Diags.second) {
+    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)) 
+                            ? origParentScope : independentParentScope);
+
+  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;
+    }
+    // Fall through
+      
+  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;
+
+  default:
+    break;
+  }
+
+  for (Stmt::child_range CI = S->children(); CI; ++CI) {
+    if (SkipFirstSubStmt) {
+      SkipFirstSubStmt = false;
+      continue;
+    }
+    
+    Stmt *SubStmt = *CI;
+    if (SubStmt == 0) continue;
+
+    // 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 (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 (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end();
+           I != E; ++I)
+        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 any part of a C++ try statement. This is pretty
+    // much the same as for Obj-C.
+    if (CXXTryStmt *TS = dyn_cast<CXXTryStmt>(SubStmt)) {
+      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));
+      }
+
+      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;
+    }
+    
+    if (const BlockExpr *BE = dyn_cast<BlockExpr>(SubStmt)) {
+        const BlockDecl *BDecl = BE->getBlockDecl();
+        for (BlockDecl::capture_const_iterator ci = BDecl->capture_begin(),
+             ce = BDecl->capture_end(); ci != ce; ++ci) {
+          VarDecl *variable = ci->getVariable();
+          BuildScopeInformation(variable, BDecl, ParentScope);
+        }
+    }
+    
+    // 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)) {
+      CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),
+                diag::err_goto_into_protected_scope,
+                diag::warn_goto_into_protected_scope,
+                diag::warn_cxx98_compat_goto_into_protected_scope);
+      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::warn_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()) {
+      assert(LabelAndGotoScopes.count(SC) && "Case not visited?");
+      CheckJump(SS, SC, SC->getLocStart(),
+                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;
+      assert(LabelAndGotoScopes.count(IG) &&
+             "indirect jump didn't get added to scopes?");
+      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;
+    assert(LabelAndGotoScopes.count(TheLabel->getStmt()) &&
+           "Referenced label didn't get added to scopes?");
+    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().CPlusPlus0x &&
+         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) {
+  assert(!ToScopes.empty());
+  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) {
+  assert(JumpScope != TargetScope);
+
+  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) {
+  assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?");
+  unsigned FromScope = LabelAndGotoScopes[From];
+
+  assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?");
+  unsigned ToScope = LabelAndGotoScopes[To];
+
+  // Common case: exactly the same scope, which is fine.
+  if (FromScope == ToScope) return;
+
+  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().MicrosoftMode && 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 Sema::DiagnoseInvalidJumps(Stmt *Body) {
+  (void)JumpScopeChecker(Body, *this);
+}