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//===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- C++ -*-=//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// 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<Stmt*, 4> IndirectJumps;
SmallVector<Stmt*, 4> AsmJumps;
SmallVector<LabelDecl*, 4> IndirectJumpTargets;
SmallVector<LabelDecl*, 4> AsmJumpTargets;
JumpScopeChecker(Stmt *Body, Sema &S);
void BuildScopeInformation(Decl *D, unsigned &ParentScope);
void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,
unsigned &ParentScope);
void BuildScopeInformation(Stmt *S, unsigned &origParentScope);
void VerifyJumps();
void VerifyIndirectOrAsmJumps(bool IsAsmGoto);
void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);
void DiagnoseIndirectOrAsmJump(Stmt *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)))
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.
/// 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,
if (VD->hasAttr<CleanupAttr>())
return ScopePair(diag::note_protected_by_cleanup,
if (VD->hasLocalStorage()) {
switch (VD->getType().isDestructedType()) {
case QualType::DK_objc_strong_lifetime:
return ScopePair(diag::note_protected_by_objc_strong_init,
case QualType::DK_objc_weak_lifetime:
return ScopePair(diag::note_protected_by_objc_weak_init,
case QualType::DK_nontrivial_c_struct:
return ScopePair(diag::note_protected_by_non_trivial_c_struct_init,
case QualType::DK_cxx_destructor:
OutDiag = diag::note_exits_dtor;
case QualType::DK_none:
const Expr *Init = VD->getInit();
if (S.Context.getLangOpts().CPlusPlus && VD->hasLocalStorage() && Init) {
// 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() &&
VD->getInitStyle() == VarDecl::CallInit) {
if (OutDiag)
InDiag = diag::note_protected_by_variable_nontriv_destructor;
else if (!Ctor->getParent()->isPOD())
InDiag = diag::note_protected_by_variable_non_pod;
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,
return ScopePair(0U, 0U);
/// 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.second) {
Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second,
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);
/// 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>())
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,
case QualType::DK_objc_strong_lifetime:
Diags = ScopePair(diag::note_enters_block_captures_strong,
case QualType::DK_objc_weak_lifetime:
Diags = ScopePair(diag::note_enters_block_captures_weak,
case QualType::DK_nontrivial_c_struct:
Diags = ScopePair(diag::note_enters_block_captures_non_trivial_c_struct,
case QualType::DK_none:
llvm_unreachable("non-lifetime captured variable");
SourceLocation Loc = D->getLocation();
if (Loc.isInvalid())
Loc = BDecl->getLocation();
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);
unsigned StmtsToSkip = 0u;
// If we found a label, remember that it is in ParentScope scope.
switch (S->getStmtClass()) {
case Stmt::AddrLabelExprClass:
case Stmt::ObjCForCollectionStmtClass: {
auto *CS = cast<ObjCForCollectionStmt>(S);
unsigned Diag = diag::note_protected_by_objc_fast_enumeration;
unsigned NewParentScope = Scopes.size();
Scopes.push_back(GotoScope(ParentScope, Diag, 0, S->getBeginLoc()));
BuildScopeInformation(CS->getBody(), NewParentScope);
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;
LabelAndGotoScopes[S] = ParentScope;
case Stmt::SwitchStmtClass:
// Evaluate the C++17 init stmt and condition variable
// before entering the scope of the switch statement.
if (Stmt *Init = cast<SwitchStmt>(S)->getInit()) {
BuildScopeInformation(Init, ParentScope);
if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) {
BuildScopeInformation(Var, ParentScope);
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;
case Stmt::GCCAsmStmtClass:
if (auto *GS = dyn_cast<GCCAsmStmt>(S))
if (GS->isAsmGoto()) {
// 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;
for (auto *E : GS->labels())
case Stmt::IfStmtClass: {
IfStmt *IS = cast<IfStmt>(S);
if (!(IS->isConstexpr() || IS->isObjCAvailabilityCheck()))
unsigned Diag = IS->isConstexpr() ? diag::note_protected_by_constexpr_if
: diag::note_protected_by_if_available;
if (VarDecl *Var = IS->getConditionVariable())
BuildScopeInformation(Var, ParentScope);
// Cannot jump into the middle of the condition.
unsigned NewParentScope = Scopes.size();
Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
BuildScopeInformation(IS->getCond(), NewParentScope);
// Jumps into either arm of an 'if constexpr' are not allowed.
NewParentScope = Scopes.size();
Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
BuildScopeInformation(IS->getThen(), NewParentScope);
if (Stmt *Else = IS->getElse()) {
NewParentScope = Scopes.size();
Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
BuildScopeInformation(Else, NewParentScope);
case Stmt::CXXTryStmtClass: {
CXXTryStmt *TS = cast<CXXTryStmt>(S);
unsigned NewParentScope = Scopes.size();
if (Stmt *TryBlock = TS->getTryBlock())
BuildScopeInformation(TryBlock, NewParentScope);
// 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);
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(CS->getHandlerBlock(), NewParentScope);
case Stmt::SEHTryStmtClass: {
SEHTryStmt *TS = cast<SEHTryStmt>(S);
unsigned NewParentScope = Scopes.size();
if (Stmt *TryBlock = TS->getTryBlock())
BuildScopeInformation(TryBlock, NewParentScope);
// Jump from __except or __finally into the __try are not allowed either.
if (SEHExceptStmt *Except = TS->getExceptHandler()) {
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(Except->getBlock(), NewParentScope);
} else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) {
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(Finally->getBlock(), NewParentScope);
case Stmt::DeclStmtClass: {
// If this is a declstmt with a VLA definition, it defines a scope from here
// to the end of the containing context.
DeclStmt *DS = cast<DeclStmt>(S);
// 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, origParentScope);
case Stmt::ObjCAtTryStmtClass: {
// Disallow jumps into any part of an @try statement by pushing a scope and
// walking all sub-stmts in that scope.
ObjCAtTryStmt *AT = cast<ObjCAtTryStmt>(S);
// Recursively walk the AST for the @try part.
unsigned NewParentScope = Scopes.size();
if (Stmt *TryPart = AT->getTryBody())
BuildScopeInformation(TryPart, NewParentScope);
// 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);
unsigned NewParentScope = Scopes.size();
// @catches are nested and it isn't
BuildScopeInformation(AC->getCatchBody(), NewParentScope);
// Jump from the finally to the try or catch is not valid.
if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(AF, NewParentScope);
case Stmt::ObjCAtSynchronizedStmtClass: {
// Disallow jumps into the protected statement of an @synchronized, but
// allow jumps into the object expression it protects.
ObjCAtSynchronizedStmt *AS = cast<ObjCAtSynchronizedStmt>(S);
// 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.
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(AS->getSynchBody(), NewParentScope);
case Stmt::ObjCAutoreleasePoolStmtClass: {
// Disallow jumps into the protected statement of an @autoreleasepool.
ObjCAutoreleasePoolStmt *AS = cast<ObjCAutoreleasePoolStmt>(S);
// Recursively walk the AST for the @autoreleasepool part, protected by a
// new scope.
unsigned NewParentScope = Scopes.size();
BuildScopeInformation(AS->getSubStmt(), NewParentScope);
case Stmt::ExprWithCleanupsClass: {
// 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.
ExprWithCleanups *EWC = cast<ExprWithCleanups>(S);
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, origParentScope);
case Stmt::MaterializeTemporaryExprClass: {
// Disallow jumps out of scopes containing temporaries lifetime-extended to
// automatic storage duration.
MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(S);
if (MTE->getStorageDuration() == SD_Automatic) {
SmallVector<const Expr *, 4> CommaLHS;
SmallVector<SubobjectAdjustment, 4> Adjustments;
const Expr *ExtendedObject =
CommaLHS, Adjustments);
if (ExtendedObject->getType().isDestructedType()) {
Scopes.push_back(GotoScope(ParentScope, 0,
origParentScope = Scopes.size()-1;
case Stmt::CaseStmtClass:
case Stmt::DefaultStmtClass:
case Stmt::LabelStmtClass:
LabelAndGotoScopes[S] = ParentScope;
for (Stmt *SubStmt : S->children()) {
if (!SubStmt)
if (StmtsToSkip) {
// 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 (SwitchCase *SC = dyn_cast<SwitchCase>(SubStmt))
Next = SC->getSubStmt();
else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt))
Next = LS->getSubStmt();
LabelAndGotoScopes[SubStmt] = ParentScope;
SubStmt = Next;
// 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(),
// 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(),
SwitchStmt *SS = cast<SwitchStmt>(Jump);
for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
SC = SC->getNextSwitchCase()) {
if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC)))
SourceLocation Loc;
if (CaseStmt *CS = dyn_cast<CaseStmt>(SC))
Loc = CS->getBeginLoc();
else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC))
Loc = DS->getBeginLoc();
Loc = SC->getBeginLoc();
CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,
/// VerifyIndirectOrAsmJumps - Verify whether any possible indirect goto or
/// asm goto jump might cross a protection boundary. Unlike direct jumps,
/// indirect or asm goto 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/asm jump is "trivial" if it bypasses no
/// initializations and no teardowns. More formally, an indirect/asm 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::VerifyIndirectOrAsmJumps(bool IsAsmGoto) {
SmallVector<Stmt*, 4> GotoJumps = IsAsmGoto ? AsmJumps : IndirectJumps;
if (GotoJumps.empty())
SmallVector<LabelDecl *, 4> JumpTargets =
IsAsmGoto ? AsmJumpTargets : IndirectJumpTargets;
// If there aren't any address-of-label expressions in this function,
// complain about the first indirect goto.
if (JumpTargets.empty()) {
assert(!IsAsmGoto &&"only indirect goto can get here");
// Collect a single representative of every scope containing an
// indirect or asm 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, Stmt*> JumpScope;
SmallVector<JumpScope, 32> JumpScopes;
llvm::DenseMap<unsigned, Stmt*> JumpScopesMap;
for (SmallVectorImpl<Stmt *>::iterator I = GotoJumps.begin(),
E = GotoJumps.end();
I != E; ++I) {
Stmt *IG = *I;
if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG)))
unsigned IGScope = LabelAndGotoScopes[IG];
Stmt *&Entry = JumpScopesMap[IGScope];
if (!Entry) Entry = IG;
for (llvm::DenseMap<unsigned, Stmt *>::iterator I = JumpScopesMap.begin(),
E = JumpScopesMap.end();
I != E; ++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 = JumpTargets.begin(),
E = JumpTargets.end();
I != E; ++I) {
LabelDecl *TheLabel = *I;
if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt())))
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;
// 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) {
// 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)
IsReachable = true;
// 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;
DiagnoseIndirectOrAsmJump(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 DiagnoseIndirectOrAsmJumpStmt(Sema &S, Stmt *Jump,
LabelDecl *Target, bool &Diagnosed) {
if (Diagnosed)
bool IsAsmGoto = isa<GCCAsmStmt>(Jump);
S.Diag(Jump->getBeginLoc(), diag::err_indirect_goto_in_protected_scope)
<< IsAsmGoto;
S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
<< IsAsmGoto;
Diagnosed = true;
/// Produce note diagnostics for a jump into a protected scope.
void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {
if (CHECK_PERMISSIVE(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::DiagnoseIndirectOrAsmJump(Stmt *Jump, unsigned JumpScope,
LabelDecl *Target,
unsigned TargetScope) {
if (CHECK_PERMISSIVE(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) {
DiagnoseIndirectOrAsmJumpStmt(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))
else if (Scopes[I].InDiag) {
DiagnoseIndirectOrAsmJumpStmt(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()) {
bool IsAsmGoto = isa<GCCAsmStmt>(Jump);
<< IsAsmGoto;
S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
<< IsAsmGoto;
/// 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)))
if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To)))
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->getBeginLoc(), diag::warn_jump_out_of_seh_finally);
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))
else if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
else if (Scopes[I].InDiag)
// Handle warnings.
if (!ToScopesWarning.empty()) {
S.Diag(DiagLoc, JumpDiagWarning);
// Handle errors.
if (!ToScopesError.empty()) {
S.Diag(DiagLoc, JumpDiagError);
// Handle -Wc++98-compat warnings if the jump is well-formed.
if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) {
S.Diag(DiagLoc, JumpDiagCXX98Compat);
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);