lib/Sema/JumpDiagnostics.cpp - platform/external/clang - Gitiles

 //===--- JumpDiagnostics.cpp - Analyze Jump Targets for VLA issues --------===//
 //
 //                     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 VLA scope in an invalid way.
 //
 //===----------------------------------------------------------------------===//

 #include "Sema.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/StmtObjC.h"
 #include "clang/AST/StmtCXX.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;

     /// Diag - The diagnostic to emit if there is a jump into this scope.
     unsigned Diag;

     /// Loc - Location to emit the diagnostic.
     SourceLocation Loc;

     GotoScope(unsigned parentScope, unsigned diag, SourceLocation L)
     : ParentScope(parentScope), Diag(diag), Loc(L) {}
   };

   llvm::SmallVector<GotoScope, 48> Scopes;
   llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
   llvm::SmallVector<Stmt*, 16> Jumps;
 public:
   JumpScopeChecker(Stmt *Body, Sema &S);
 private:
   void BuildScopeInformation(Stmt *S, unsigned ParentScope);
   void VerifyJumps();
   void CheckJump(Stmt *From, Stmt *To,
                  SourceLocation DiagLoc, unsigned JumpDiag);
 };
 } // end anonymous namespace


 JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
   // Add a scope entry for function scope.
   Scopes.push_back(GotoScope(~0U, ~0U, SourceLocation()));

   // Build information for the top level compound statement, so that we have a
   // defined scope record for every "goto" and label.
   BuildScopeInformation(Body, 0);

   // Check that all jumps we saw are kosher.
   VerifyJumps();
 }

 /// 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 unsigned GetDiagForGotoScopeDecl(const Decl *D) {
   if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
     if (VD->getType()->isVariablyModifiedType())
       return diag::note_protected_by_vla;
     if (VD->hasAttr<CleanupAttr>())
       return diag::note_protected_by_cleanup;
     if (VD->hasAttr<BlocksAttr>())
       return diag::note_protected_by___block;
   } else if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
     if (TD->getUnderlyingType()->isVariablyModifiedType())
       return diag::note_protected_by_vla_typedef;
   }

   return 0;
 }


 /// 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 ParentScope) {

   // If we found a label, remember that it is in ParentScope scope.
   if (isa<LabelStmt>(S) || isa<DefaultStmt>(S) || isa<CaseStmt>(S)) {
     LabelAndGotoScopes[S] = ParentScope;
   } else if (isa<GotoStmt>(S) || isa<SwitchStmt>(S) ||
              isa<IndirectGotoStmt>(S) || isa<AddrLabelExpr>(S)) {
     // 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);
   }

   for (Stmt::child_iterator CI = S->child_begin(), E = S->child_end(); CI != E;
        ++CI) {
     Stmt *SubStmt = *CI;
     if (SubStmt == 0) continue;

     // FIXME: diagnose jumps past initialization: required in C++, warning in C.
     //   goto L; int X = 4;   L: ;

     // 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) {
         // If this decl causes a new scope, push and switch to it.
         if (unsigned Diag = GetDiagForGotoScopeDecl(*I)) {
           Scopes.push_back(GotoScope(ParentScope, Diag, (*I)->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>(*I))
           if (Expr *Init = VD->getInit())
             BuildScopeInformation(Init, 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)) {
       // Recursively walk the AST for the @try part.
       Scopes.push_back(GotoScope(ParentScope,diag::note_protected_by_objc_try,
                                  AT->getAtTryLoc()));
       if (Stmt *TryPart = AT->getTryBody())
         BuildScopeInformation(TryPart, Scopes.size()-1);

       // Jump from the catch to the finally or try is not valid.
       for (ObjCAtCatchStmt *AC = AT->getCatchStmts(); AC;
            AC = AC->getNextCatchStmt()) {
         Scopes.push_back(GotoScope(ParentScope,
                                    diag::note_protected_by_objc_catch,
                                    AC->getAtCatchLoc()));
         // @catches are nested and it isn't
         BuildScopeInformation(AC->getCatchBody(), 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,
                                    AF->getAtFinallyLoc()));
         BuildScopeInformation(AF, Scopes.size()-1);
       }

       continue;
     }

     // 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,
                                  AS->getAtSynchronizedLoc()));
       BuildScopeInformation(AS->getSynchBody(), 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,
                                  TS->getSourceRange().getBegin()));
       if (Stmt *TryBlock = TS->getTryBlock())
         BuildScopeInformation(TryBlock, 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,
                                    CS->getSourceRange().getBegin()));
         BuildScopeInformation(CS->getHandlerBlock(), Scopes.size()-1);
       }

       continue;
     }

     // 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(), GS->getGotoLoc(),
                 diag::err_goto_into_protected_scope);
       continue;
     }

     if (SwitchStmt *SS = dyn_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);
       }
       continue;
     }

     unsigned DiagnosticScope;

     // We don't know where an indirect goto goes, require that it be at the
     // top level of scoping.
     if (IndirectGotoStmt *IG = dyn_cast<IndirectGotoStmt>(Jump)) {
       assert(LabelAndGotoScopes.count(Jump) &&
              "Jump didn't get added to scopes?");
       unsigned GotoScope = LabelAndGotoScopes[IG];
       if (GotoScope == 0) continue;  // indirect jump is ok.
       S.Diag(IG->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
       DiagnosticScope = GotoScope;
     } else {
       // We model &&Label as a jump for purposes of scope tracking.  We actually
       // don't care *where* the address of label is, but we require the *label
       // itself* to be in scope 0.  If it is nested inside of a VLA scope, then
       // it is possible for an indirect goto to illegally enter the VLA scope by
       // indirectly jumping to the label.
       assert(isa<AddrLabelExpr>(Jump) && "Unknown jump type");
       LabelStmt *TheLabel = cast<AddrLabelExpr>(Jump)->getLabel();

       assert(LabelAndGotoScopes.count(TheLabel) &&
              "Referenced label didn't get added to scopes?");
       unsigned LabelScope = LabelAndGotoScopes[TheLabel];
       if (LabelScope == 0) continue; // Addr of label is ok.

       S.Diag(Jump->getLocStart(), diag::err_addr_of_label_in_protected_scope);
       DiagnosticScope = LabelScope;
     }

     // Report all the things that would be skipped over by this &&label or
     // indirect goto.
     while (DiagnosticScope != 0) {
       S.Diag(Scopes[DiagnosticScope].Loc, Scopes[DiagnosticScope].Diag);
       DiagnosticScope = Scopes[DiagnosticScope].ParentScope;
     }
   }
 }

 /// 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 JumpDiag) {
   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;

   // The only valid mismatch jump case happens when the jump is more deeply
   // nested inside the jump target.  Do a quick scan to see if the jump is valid
   // because valid code is more common than invalid code.
   unsigned TestScope = Scopes[FromScope].ParentScope;
   while (TestScope != ~0U) {
     // If we found the jump target, then we're jumping out of our current scope,
     // which is perfectly fine.
     if (TestScope == ToScope) return;

     // Otherwise, scan up the hierarchy.
     TestScope = Scopes[TestScope].ParentScope;
   }

   // If we get here, then we know we have invalid code.  Diagnose the bad jump,
   // and then emit a note at each VLA being jumped out of.
   S.Diag(DiagLoc, JumpDiag);

   // Eliminate the common prefix of the jump and the target.  Start by
   // linearizing both scopes, reversing them as we go.
   std::vector<unsigned> FromScopes, ToScopes;
   for (TestScope = FromScope; TestScope != ~0U;
        TestScope = Scopes[TestScope].ParentScope)
     FromScopes.push_back(TestScope);
   for (TestScope = ToScope; TestScope != ~0U;
        TestScope = Scopes[TestScope].ParentScope)
     ToScopes.push_back(TestScope);

   // Remove any common entries (such as the top-level function scope).
   while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) {
     FromScopes.pop_back();
     ToScopes.pop_back();
   }

   // Emit diagnostics for whatever is left in ToScopes.
   for (unsigned i = 0, e = ToScopes.size(); i != e; ++i)
     S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag);
 }

 void Sema::DiagnoseInvalidJumps(Stmt *Body) {
   JumpScopeChecker(Body, *this);
 }
	//===--- JumpDiagnostics.cpp - Analyze Jump Targets for VLA issues --------===//
	//
	// 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 VLA scope in an invalid way.
	//
	//===----------------------------------------------------------------------===//

	#include "Sema.h"
	#include "clang/AST/Expr.h"
	#include "clang/AST/StmtObjC.h"
	#include "clang/AST/StmtCXX.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;

	/// Diag - The diagnostic to emit if there is a jump into this scope.
	unsigned Diag;

	/// Loc - Location to emit the diagnostic.
	SourceLocation Loc;

	GotoScope(unsigned parentScope, unsigned diag, SourceLocation L)
	: ParentScope(parentScope), Diag(diag), Loc(L) {}
	};

	llvm::SmallVector<GotoScope, 48> Scopes;
	llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
	llvm::SmallVector<Stmt*, 16> Jumps;
	public:
	JumpScopeChecker(Stmt *Body, Sema &S);
	private:
	void BuildScopeInformation(Stmt *S, unsigned ParentScope);
	void VerifyJumps();
	void CheckJump(Stmt From, Stmt To,
	SourceLocation DiagLoc, unsigned JumpDiag);
	};
	} // end anonymous namespace


	JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
	// Add a scope entry for function scope.
	Scopes.push_back(GotoScope(~0U, ~0U, SourceLocation()));

	// Build information for the top level compound statement, so that we have a
	// defined scope record for every "goto" and label.
	BuildScopeInformation(Body, 0);

	// Check that all jumps we saw are kosher.
	VerifyJumps();
	}

	/// 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 unsigned GetDiagForGotoScopeDecl(const Decl *D) {
	if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
	if (VD->getType()->isVariablyModifiedType())
	return diag::note_protected_by_vla;
	if (VD->hasAttr<CleanupAttr>())
	return diag::note_protected_by_cleanup;
	if (VD->hasAttr<BlocksAttr>())
	return diag::note_protected_by___block;
	} else if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
	if (TD->getUnderlyingType()->isVariablyModifiedType())
	return diag::note_protected_by_vla_typedef;
	}

	return 0;
	}


	/// 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 ParentScope) {

	// If we found a label, remember that it is in ParentScope scope.
	if (isa<LabelStmt>(S) \|\| isa<DefaultStmt>(S) \|\| isa<CaseStmt>(S)) {
	LabelAndGotoScopes[S] = ParentScope;
	} else if (isa<GotoStmt>(S) \|\| isa<SwitchStmt>(S) \|\|
	isa<IndirectGotoStmt>(S) \|\| isa<AddrLabelExpr>(S)) {
	// 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);
	}

	for (Stmt::child_iterator CI = S->child_begin(), E = S->child_end(); CI != E;
	++CI) {
	Stmt SubStmt = CI;
	if (SubStmt == 0) continue;

	// FIXME: diagnose jumps past initialization: required in C++, warning in C.
	// goto L; int X = 4; L: ;

	// 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) {
	// If this decl causes a new scope, push and switch to it.
	if (unsigned Diag = GetDiagForGotoScopeDecl(*I)) {
	Scopes.push_back(GotoScope(ParentScope, Diag, (*I)->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>(I))
	if (Expr *Init = VD->getInit())
	BuildScopeInformation(Init, 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)) {
	// Recursively walk the AST for the @try part.
	Scopes.push_back(GotoScope(ParentScope,diag::note_protected_by_objc_try,
	AT->getAtTryLoc()));
	if (Stmt *TryPart = AT->getTryBody())
	BuildScopeInformation(TryPart, Scopes.size()-1);

	// Jump from the catch to the finally or try is not valid.
	for (ObjCAtCatchStmt *AC = AT->getCatchStmts(); AC;
	AC = AC->getNextCatchStmt()) {
	Scopes.push_back(GotoScope(ParentScope,
	diag::note_protected_by_objc_catch,
	AC->getAtCatchLoc()));
	// @catches are nested and it isn't
	BuildScopeInformation(AC->getCatchBody(), 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,
	AF->getAtFinallyLoc()));
	BuildScopeInformation(AF, Scopes.size()-1);
	}

	continue;
	}

	// 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,
	AS->getAtSynchronizedLoc()));
	BuildScopeInformation(AS->getSynchBody(), 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,
	TS->getSourceRange().getBegin()));
	if (Stmt *TryBlock = TS->getTryBlock())
	BuildScopeInformation(TryBlock, 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,
	CS->getSourceRange().getBegin()));
	BuildScopeInformation(CS->getHandlerBlock(), Scopes.size()-1);
	}

	continue;
	}

	// 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(), GS->getGotoLoc(),
	diag::err_goto_into_protected_scope);
	continue;
	}

	if (SwitchStmt *SS = dyn_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);
	}
	continue;
	}

	unsigned DiagnosticScope;

	// We don't know where an indirect goto goes, require that it be at the
	// top level of scoping.
	if (IndirectGotoStmt *IG = dyn_cast<IndirectGotoStmt>(Jump)) {
	assert(LabelAndGotoScopes.count(Jump) &&
	"Jump didn't get added to scopes?");
	unsigned GotoScope = LabelAndGotoScopes[IG];
	if (GotoScope == 0) continue; // indirect jump is ok.
	S.Diag(IG->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
	DiagnosticScope = GotoScope;
	} else {
	// We model &&Label as a jump for purposes of scope tracking. We actually
	// don't care where the address of label is, but we require the *label
	// itself* to be in scope 0. If it is nested inside of a VLA scope, then
	// it is possible for an indirect goto to illegally enter the VLA scope by
	// indirectly jumping to the label.
	assert(isa<AddrLabelExpr>(Jump) && "Unknown jump type");
	LabelStmt *TheLabel = cast<AddrLabelExpr>(Jump)->getLabel();

	assert(LabelAndGotoScopes.count(TheLabel) &&
	"Referenced label didn't get added to scopes?");
	unsigned LabelScope = LabelAndGotoScopes[TheLabel];
	if (LabelScope == 0) continue; // Addr of label is ok.

	S.Diag(Jump->getLocStart(), diag::err_addr_of_label_in_protected_scope);
	DiagnosticScope = LabelScope;
	}

	// Report all the things that would be skipped over by this &&label or
	// indirect goto.
	while (DiagnosticScope != 0) {
	S.Diag(Scopes[DiagnosticScope].Loc, Scopes[DiagnosticScope].Diag);
	DiagnosticScope = Scopes[DiagnosticScope].ParentScope;
	}
	}
	}

	/// 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 JumpDiag) {
	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;

	// The only valid mismatch jump case happens when the jump is more deeply
	// nested inside the jump target. Do a quick scan to see if the jump is valid
	// because valid code is more common than invalid code.
	unsigned TestScope = Scopes[FromScope].ParentScope;
	while (TestScope != ~0U) {
	// If we found the jump target, then we're jumping out of our current scope,
	// which is perfectly fine.
	if (TestScope == ToScope) return;

	// Otherwise, scan up the hierarchy.
	TestScope = Scopes[TestScope].ParentScope;
	}

	// If we get here, then we know we have invalid code. Diagnose the bad jump,
	// and then emit a note at each VLA being jumped out of.
	S.Diag(DiagLoc, JumpDiag);

	// Eliminate the common prefix of the jump and the target. Start by
	// linearizing both scopes, reversing them as we go.
	std::vector<unsigned> FromScopes, ToScopes;
	for (TestScope = FromScope; TestScope != ~0U;
	TestScope = Scopes[TestScope].ParentScope)
	FromScopes.push_back(TestScope);
	for (TestScope = ToScope; TestScope != ~0U;
	TestScope = Scopes[TestScope].ParentScope)
	ToScopes.push_back(TestScope);

	// Remove any common entries (such as the top-level function scope).
	while (!FromScopes.empty() && FromScopes.back() == ToScopes.back()) {
	FromScopes.pop_back();
	ToScopes.pop_back();
	}

	// Emit diagnostics for whatever is left in ToScopes.
	for (unsigned i = 0, e = ToScopes.size(); i != e; ++i)
	S.Diag(Scopes[ToScopes[i]].Loc, Scopes[ToScopes[i]].Diag);
	}

	void Sema::DiagnoseInvalidJumps(Stmt *Body) {
	JumpScopeChecker(Body, *this);
	}