1 //===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- C++ -*-=//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the JumpScopeChecker class, which is used to diagnose
10 // jumps that enter a protected scope in an invalid way.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/Sema/SemaInternal.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/Expr.h"
17 #include "clang/AST/ExprCXX.h"
18 #include "clang/AST/StmtCXX.h"
19 #include "clang/AST/StmtObjC.h"
20 #include "llvm/ADT/BitVector.h"
21 using namespace clang;
22
23 namespace {
24
25 /// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps
26 /// into VLA and other protected scopes. For example, this rejects:
27 /// goto L;
28 /// int a[n];
29 /// L:
30 ///
31 class JumpScopeChecker {
32 Sema &S;
33
34 /// Permissive - True when recovering from errors, in which case precautions
35 /// are taken to handle incomplete scope information.
36 const bool Permissive;
37
38 /// GotoScope - This is a record that we use to keep track of all of the
39 /// scopes that are introduced by VLAs and other things that scope jumps like
40 /// gotos. This scope tree has nothing to do with the source scope tree,
41 /// because you can have multiple VLA scopes per compound statement, and most
42 /// compound statements don't introduce any scopes.
43 struct GotoScope {
44 /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
45 /// the parent scope is the function body.
46 unsigned ParentScope;
47
48 /// InDiag - The note to emit if there is a jump into this scope.
49 unsigned InDiag;
50
51 /// OutDiag - The note to emit if there is an indirect jump out
52 /// of this scope. Direct jumps always clean up their current scope
53 /// in an orderly way.
54 unsigned OutDiag;
55
56 /// Loc - Location to emit the diagnostic.
57 SourceLocation Loc;
58
GotoScope__anon70c4aa930111::JumpScopeChecker::GotoScope59 GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag,
60 SourceLocation L)
61 : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {}
62 };
63
64 SmallVector<GotoScope, 48> Scopes;
65 llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
66 SmallVector<Stmt*, 16> Jumps;
67
68 SmallVector<Stmt*, 4> IndirectJumps;
69 SmallVector<Stmt*, 4> AsmJumps;
70 SmallVector<LabelDecl*, 4> IndirectJumpTargets;
71 SmallVector<LabelDecl*, 4> AsmJumpTargets;
72 public:
73 JumpScopeChecker(Stmt *Body, Sema &S);
74 private:
75 void BuildScopeInformation(Decl *D, unsigned &ParentScope);
76 void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,
77 unsigned &ParentScope);
78 void BuildScopeInformation(Stmt *S, unsigned &origParentScope);
79
80 void VerifyJumps();
81 void VerifyIndirectOrAsmJumps(bool IsAsmGoto);
82 void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);
83 void DiagnoseIndirectOrAsmJump(Stmt *IG, unsigned IGScope, LabelDecl *Target,
84 unsigned TargetScope);
85 void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
86 unsigned JumpDiag, unsigned JumpDiagWarning,
87 unsigned JumpDiagCXX98Compat);
88 void CheckGotoStmt(GotoStmt *GS);
89
90 unsigned GetDeepestCommonScope(unsigned A, unsigned B);
91 };
92 } // end anonymous namespace
93
94 #define CHECK_PERMISSIVE(x) (assert(Permissive || !(x)), (Permissive && (x)))
95
JumpScopeChecker(Stmt * Body,Sema & s)96 JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s)
97 : S(s), Permissive(s.hasAnyUnrecoverableErrorsInThisFunction()) {
98 // Add a scope entry for function scope.
99 Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation()));
100
101 // Build information for the top level compound statement, so that we have a
102 // defined scope record for every "goto" and label.
103 unsigned BodyParentScope = 0;
104 BuildScopeInformation(Body, BodyParentScope);
105
106 // Check that all jumps we saw are kosher.
107 VerifyJumps();
108 VerifyIndirectOrAsmJumps(false);
109 VerifyIndirectOrAsmJumps(true);
110 }
111
112 /// GetDeepestCommonScope - Finds the innermost scope enclosing the
113 /// two scopes.
GetDeepestCommonScope(unsigned A,unsigned B)114 unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) {
115 while (A != B) {
116 // Inner scopes are created after outer scopes and therefore have
117 // higher indices.
118 if (A < B) {
119 assert(Scopes[B].ParentScope < B);
120 B = Scopes[B].ParentScope;
121 } else {
122 assert(Scopes[A].ParentScope < A);
123 A = Scopes[A].ParentScope;
124 }
125 }
126 return A;
127 }
128
129 typedef std::pair<unsigned,unsigned> ScopePair;
130
131 /// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
132 /// diagnostic that should be emitted if control goes over it. If not, return 0.
GetDiagForGotoScopeDecl(Sema & S,const Decl * D)133 static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D) {
134 if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
135 unsigned InDiag = 0;
136 unsigned OutDiag = 0;
137
138 if (VD->getType()->isVariablyModifiedType())
139 InDiag = diag::note_protected_by_vla;
140
141 if (VD->hasAttr<BlocksAttr>())
142 return ScopePair(diag::note_protected_by___block,
143 diag::note_exits___block);
144
145 if (VD->hasAttr<CleanupAttr>())
146 return ScopePair(diag::note_protected_by_cleanup,
147 diag::note_exits_cleanup);
148
149 if (VD->hasLocalStorage()) {
150 switch (VD->getType().isDestructedType()) {
151 case QualType::DK_objc_strong_lifetime:
152 return ScopePair(diag::note_protected_by_objc_strong_init,
153 diag::note_exits_objc_strong);
154
155 case QualType::DK_objc_weak_lifetime:
156 return ScopePair(diag::note_protected_by_objc_weak_init,
157 diag::note_exits_objc_weak);
158
159 case QualType::DK_nontrivial_c_struct:
160 return ScopePair(diag::note_protected_by_non_trivial_c_struct_init,
161 diag::note_exits_dtor);
162
163 case QualType::DK_cxx_destructor:
164 OutDiag = diag::note_exits_dtor;
165 break;
166
167 case QualType::DK_none:
168 break;
169 }
170 }
171
172 const Expr *Init = VD->getInit();
173 if (S.Context.getLangOpts().CPlusPlus && VD->hasLocalStorage() && Init) {
174 // C++11 [stmt.dcl]p3:
175 // A program that jumps from a point where a variable with automatic
176 // storage duration is not in scope to a point where it is in scope
177 // is ill-formed unless the variable has scalar type, class type with
178 // a trivial default constructor and a trivial destructor, a
179 // cv-qualified version of one of these types, or an array of one of
180 // the preceding types and is declared without an initializer.
181
182 // C++03 [stmt.dcl.p3:
183 // A program that jumps from a point where a local variable
184 // with automatic storage duration is not in scope to a point
185 // where it is in scope is ill-formed unless the variable has
186 // POD type and is declared without an initializer.
187
188 InDiag = diag::note_protected_by_variable_init;
189
190 // For a variable of (array of) class type declared without an
191 // initializer, we will have call-style initialization and the initializer
192 // will be the CXXConstructExpr with no intervening nodes.
193 if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Init)) {
194 const CXXConstructorDecl *Ctor = CCE->getConstructor();
195 if (Ctor->isTrivial() && Ctor->isDefaultConstructor() &&
196 VD->getInitStyle() == VarDecl::CallInit) {
197 if (OutDiag)
198 InDiag = diag::note_protected_by_variable_nontriv_destructor;
199 else if (!Ctor->getParent()->isPOD())
200 InDiag = diag::note_protected_by_variable_non_pod;
201 else
202 InDiag = 0;
203 }
204 }
205 }
206
207 return ScopePair(InDiag, OutDiag);
208 }
209
210 if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(D)) {
211 if (TD->getUnderlyingType()->isVariablyModifiedType())
212 return ScopePair(isa<TypedefDecl>(TD)
213 ? diag::note_protected_by_vla_typedef
214 : diag::note_protected_by_vla_type_alias,
215 0);
216 }
217
218 return ScopePair(0U, 0U);
219 }
220
221 /// Build scope information for a declaration that is part of a DeclStmt.
BuildScopeInformation(Decl * D,unsigned & ParentScope)222 void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) {
223 // If this decl causes a new scope, push and switch to it.
224 std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S, D);
225 if (Diags.first || Diags.second) {
226 Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second,
227 D->getLocation()));
228 ParentScope = Scopes.size()-1;
229 }
230
231 // If the decl has an initializer, walk it with the potentially new
232 // scope we just installed.
233 if (VarDecl *VD = dyn_cast<VarDecl>(D))
234 if (Expr *Init = VD->getInit())
235 BuildScopeInformation(Init, ParentScope);
236 }
237
238 /// Build scope information for a captured block literal variables.
BuildScopeInformation(VarDecl * D,const BlockDecl * BDecl,unsigned & ParentScope)239 void JumpScopeChecker::BuildScopeInformation(VarDecl *D,
240 const BlockDecl *BDecl,
241 unsigned &ParentScope) {
242 // exclude captured __block variables; there's no destructor
243 // associated with the block literal for them.
244 if (D->hasAttr<BlocksAttr>())
245 return;
246 QualType T = D->getType();
247 QualType::DestructionKind destructKind = T.isDestructedType();
248 if (destructKind != QualType::DK_none) {
249 std::pair<unsigned,unsigned> Diags;
250 switch (destructKind) {
251 case QualType::DK_cxx_destructor:
252 Diags = ScopePair(diag::note_enters_block_captures_cxx_obj,
253 diag::note_exits_block_captures_cxx_obj);
254 break;
255 case QualType::DK_objc_strong_lifetime:
256 Diags = ScopePair(diag::note_enters_block_captures_strong,
257 diag::note_exits_block_captures_strong);
258 break;
259 case QualType::DK_objc_weak_lifetime:
260 Diags = ScopePair(diag::note_enters_block_captures_weak,
261 diag::note_exits_block_captures_weak);
262 break;
263 case QualType::DK_nontrivial_c_struct:
264 Diags = ScopePair(diag::note_enters_block_captures_non_trivial_c_struct,
265 diag::note_exits_block_captures_non_trivial_c_struct);
266 break;
267 case QualType::DK_none:
268 llvm_unreachable("non-lifetime captured variable");
269 }
270 SourceLocation Loc = D->getLocation();
271 if (Loc.isInvalid())
272 Loc = BDecl->getLocation();
273 Scopes.push_back(GotoScope(ParentScope,
274 Diags.first, Diags.second, Loc));
275 ParentScope = Scopes.size()-1;
276 }
277 }
278
279 /// BuildScopeInformation - The statements from CI to CE are known to form a
280 /// coherent VLA scope with a specified parent node. Walk through the
281 /// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
282 /// walking the AST as needed.
BuildScopeInformation(Stmt * S,unsigned & origParentScope)283 void JumpScopeChecker::BuildScopeInformation(Stmt *S,
284 unsigned &origParentScope) {
285 // If this is a statement, rather than an expression, scopes within it don't
286 // propagate out into the enclosing scope. Otherwise we have to worry
287 // about block literals, which have the lifetime of their enclosing statement.
288 unsigned independentParentScope = origParentScope;
289 unsigned &ParentScope = ((isa<Expr>(S) && !isa<StmtExpr>(S))
290 ? origParentScope : independentParentScope);
291
292 unsigned StmtsToSkip = 0u;
293
294 // If we found a label, remember that it is in ParentScope scope.
295 switch (S->getStmtClass()) {
296 case Stmt::AddrLabelExprClass:
297 IndirectJumpTargets.push_back(cast<AddrLabelExpr>(S)->getLabel());
298 break;
299
300 case Stmt::ObjCForCollectionStmtClass: {
301 auto *CS = cast<ObjCForCollectionStmt>(S);
302 unsigned Diag = diag::note_protected_by_objc_fast_enumeration;
303 unsigned NewParentScope = Scopes.size();
304 Scopes.push_back(GotoScope(ParentScope, Diag, 0, S->getBeginLoc()));
305 BuildScopeInformation(CS->getBody(), NewParentScope);
306 return;
307 }
308
309 case Stmt::IndirectGotoStmtClass:
310 // "goto *&&lbl;" is a special case which we treat as equivalent
311 // to a normal goto. In addition, we don't calculate scope in the
312 // operand (to avoid recording the address-of-label use), which
313 // works only because of the restricted set of expressions which
314 // we detect as constant targets.
315 if (cast<IndirectGotoStmt>(S)->getConstantTarget()) {
316 LabelAndGotoScopes[S] = ParentScope;
317 Jumps.push_back(S);
318 return;
319 }
320
321 LabelAndGotoScopes[S] = ParentScope;
322 IndirectJumps.push_back(S);
323 break;
324
325 case Stmt::SwitchStmtClass:
326 // Evaluate the C++17 init stmt and condition variable
327 // before entering the scope of the switch statement.
328 if (Stmt *Init = cast<SwitchStmt>(S)->getInit()) {
329 BuildScopeInformation(Init, ParentScope);
330 ++StmtsToSkip;
331 }
332 if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) {
333 BuildScopeInformation(Var, ParentScope);
334 ++StmtsToSkip;
335 }
336 LLVM_FALLTHROUGH;
337
338 case Stmt::GotoStmtClass:
339 // Remember both what scope a goto is in as well as the fact that we have
340 // it. This makes the second scan not have to walk the AST again.
341 LabelAndGotoScopes[S] = ParentScope;
342 Jumps.push_back(S);
343 break;
344
345 case Stmt::GCCAsmStmtClass:
346 if (auto *GS = dyn_cast<GCCAsmStmt>(S))
347 if (GS->isAsmGoto()) {
348 // Remember both what scope a goto is in as well as the fact that we
349 // have it. This makes the second scan not have to walk the AST again.
350 LabelAndGotoScopes[S] = ParentScope;
351 AsmJumps.push_back(GS);
352 for (auto *E : GS->labels())
353 AsmJumpTargets.push_back(E->getLabel());
354 }
355 break;
356
357 case Stmt::IfStmtClass: {
358 IfStmt *IS = cast<IfStmt>(S);
359 if (!(IS->isConstexpr() || IS->isObjCAvailabilityCheck()))
360 break;
361
362 unsigned Diag = IS->isConstexpr() ? diag::note_protected_by_constexpr_if
363 : diag::note_protected_by_if_available;
364
365 if (VarDecl *Var = IS->getConditionVariable())
366 BuildScopeInformation(Var, ParentScope);
367
368 // Cannot jump into the middle of the condition.
369 unsigned NewParentScope = Scopes.size();
370 Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
371 BuildScopeInformation(IS->getCond(), NewParentScope);
372
373 // Jumps into either arm of an 'if constexpr' are not allowed.
374 NewParentScope = Scopes.size();
375 Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
376 BuildScopeInformation(IS->getThen(), NewParentScope);
377 if (Stmt *Else = IS->getElse()) {
378 NewParentScope = Scopes.size();
379 Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
380 BuildScopeInformation(Else, NewParentScope);
381 }
382 return;
383 }
384
385 case Stmt::CXXTryStmtClass: {
386 CXXTryStmt *TS = cast<CXXTryStmt>(S);
387 {
388 unsigned NewParentScope = Scopes.size();
389 Scopes.push_back(GotoScope(ParentScope,
390 diag::note_protected_by_cxx_try,
391 diag::note_exits_cxx_try,
392 TS->getSourceRange().getBegin()));
393 if (Stmt *TryBlock = TS->getTryBlock())
394 BuildScopeInformation(TryBlock, NewParentScope);
395 }
396
397 // Jump from the catch into the try is not allowed either.
398 for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
399 CXXCatchStmt *CS = TS->getHandler(I);
400 unsigned NewParentScope = Scopes.size();
401 Scopes.push_back(GotoScope(ParentScope,
402 diag::note_protected_by_cxx_catch,
403 diag::note_exits_cxx_catch,
404 CS->getSourceRange().getBegin()));
405 BuildScopeInformation(CS->getHandlerBlock(), NewParentScope);
406 }
407 return;
408 }
409
410 case Stmt::SEHTryStmtClass: {
411 SEHTryStmt *TS = cast<SEHTryStmt>(S);
412 {
413 unsigned NewParentScope = Scopes.size();
414 Scopes.push_back(GotoScope(ParentScope,
415 diag::note_protected_by_seh_try,
416 diag::note_exits_seh_try,
417 TS->getSourceRange().getBegin()));
418 if (Stmt *TryBlock = TS->getTryBlock())
419 BuildScopeInformation(TryBlock, NewParentScope);
420 }
421
422 // Jump from __except or __finally into the __try are not allowed either.
423 if (SEHExceptStmt *Except = TS->getExceptHandler()) {
424 unsigned NewParentScope = Scopes.size();
425 Scopes.push_back(GotoScope(ParentScope,
426 diag::note_protected_by_seh_except,
427 diag::note_exits_seh_except,
428 Except->getSourceRange().getBegin()));
429 BuildScopeInformation(Except->getBlock(), NewParentScope);
430 } else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) {
431 unsigned NewParentScope = Scopes.size();
432 Scopes.push_back(GotoScope(ParentScope,
433 diag::note_protected_by_seh_finally,
434 diag::note_exits_seh_finally,
435 Finally->getSourceRange().getBegin()));
436 BuildScopeInformation(Finally->getBlock(), NewParentScope);
437 }
438
439 return;
440 }
441
442 case Stmt::DeclStmtClass: {
443 // If this is a declstmt with a VLA definition, it defines a scope from here
444 // to the end of the containing context.
445 DeclStmt *DS = cast<DeclStmt>(S);
446 // The decl statement creates a scope if any of the decls in it are VLAs
447 // or have the cleanup attribute.
448 for (auto *I : DS->decls())
449 BuildScopeInformation(I, origParentScope);
450 return;
451 }
452
453 case Stmt::ObjCAtTryStmtClass: {
454 // Disallow jumps into any part of an @try statement by pushing a scope and
455 // walking all sub-stmts in that scope.
456 ObjCAtTryStmt *AT = cast<ObjCAtTryStmt>(S);
457 // Recursively walk the AST for the @try part.
458 {
459 unsigned NewParentScope = Scopes.size();
460 Scopes.push_back(GotoScope(ParentScope,
461 diag::note_protected_by_objc_try,
462 diag::note_exits_objc_try,
463 AT->getAtTryLoc()));
464 if (Stmt *TryPart = AT->getTryBody())
465 BuildScopeInformation(TryPart, NewParentScope);
466 }
467
468 // Jump from the catch to the finally or try is not valid.
469 for (unsigned I = 0, N = AT->getNumCatchStmts(); I != N; ++I) {
470 ObjCAtCatchStmt *AC = AT->getCatchStmt(I);
471 unsigned NewParentScope = Scopes.size();
472 Scopes.push_back(GotoScope(ParentScope,
473 diag::note_protected_by_objc_catch,
474 diag::note_exits_objc_catch,
475 AC->getAtCatchLoc()));
476 // @catches are nested and it isn't
477 BuildScopeInformation(AC->getCatchBody(), NewParentScope);
478 }
479
480 // Jump from the finally to the try or catch is not valid.
481 if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
482 unsigned NewParentScope = Scopes.size();
483 Scopes.push_back(GotoScope(ParentScope,
484 diag::note_protected_by_objc_finally,
485 diag::note_exits_objc_finally,
486 AF->getAtFinallyLoc()));
487 BuildScopeInformation(AF, NewParentScope);
488 }
489
490 return;
491 }
492
493 case Stmt::ObjCAtSynchronizedStmtClass: {
494 // Disallow jumps into the protected statement of an @synchronized, but
495 // allow jumps into the object expression it protects.
496 ObjCAtSynchronizedStmt *AS = cast<ObjCAtSynchronizedStmt>(S);
497 // Recursively walk the AST for the @synchronized object expr, it is
498 // evaluated in the normal scope.
499 BuildScopeInformation(AS->getSynchExpr(), ParentScope);
500
501 // Recursively walk the AST for the @synchronized part, protected by a new
502 // scope.
503 unsigned NewParentScope = Scopes.size();
504 Scopes.push_back(GotoScope(ParentScope,
505 diag::note_protected_by_objc_synchronized,
506 diag::note_exits_objc_synchronized,
507 AS->getAtSynchronizedLoc()));
508 BuildScopeInformation(AS->getSynchBody(), NewParentScope);
509 return;
510 }
511
512 case Stmt::ObjCAutoreleasePoolStmtClass: {
513 // Disallow jumps into the protected statement of an @autoreleasepool.
514 ObjCAutoreleasePoolStmt *AS = cast<ObjCAutoreleasePoolStmt>(S);
515 // Recursively walk the AST for the @autoreleasepool part, protected by a
516 // new scope.
517 unsigned NewParentScope = Scopes.size();
518 Scopes.push_back(GotoScope(ParentScope,
519 diag::note_protected_by_objc_autoreleasepool,
520 diag::note_exits_objc_autoreleasepool,
521 AS->getAtLoc()));
522 BuildScopeInformation(AS->getSubStmt(), NewParentScope);
523 return;
524 }
525
526 case Stmt::ExprWithCleanupsClass: {
527 // Disallow jumps past full-expressions that use blocks with
528 // non-trivial cleanups of their captures. This is theoretically
529 // implementable but a lot of work which we haven't felt up to doing.
530 ExprWithCleanups *EWC = cast<ExprWithCleanups>(S);
531 for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) {
532 const BlockDecl *BDecl = EWC->getObject(i);
533 for (const auto &CI : BDecl->captures()) {
534 VarDecl *variable = CI.getVariable();
535 BuildScopeInformation(variable, BDecl, origParentScope);
536 }
537 }
538 break;
539 }
540
541 case Stmt::MaterializeTemporaryExprClass: {
542 // Disallow jumps out of scopes containing temporaries lifetime-extended to
543 // automatic storage duration.
544 MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(S);
545 if (MTE->getStorageDuration() == SD_Automatic) {
546 SmallVector<const Expr *, 4> CommaLHS;
547 SmallVector<SubobjectAdjustment, 4> Adjustments;
548 const Expr *ExtendedObject =
549 MTE->GetTemporaryExpr()->skipRValueSubobjectAdjustments(
550 CommaLHS, Adjustments);
551 if (ExtendedObject->getType().isDestructedType()) {
552 Scopes.push_back(GotoScope(ParentScope, 0,
553 diag::note_exits_temporary_dtor,
554 ExtendedObject->getExprLoc()));
555 origParentScope = Scopes.size()-1;
556 }
557 }
558 break;
559 }
560
561 case Stmt::CaseStmtClass:
562 case Stmt::DefaultStmtClass:
563 case Stmt::LabelStmtClass:
564 LabelAndGotoScopes[S] = ParentScope;
565 break;
566
567 default:
568 break;
569 }
570
571 for (Stmt *SubStmt : S->children()) {
572 if (!SubStmt)
573 continue;
574 if (StmtsToSkip) {
575 --StmtsToSkip;
576 continue;
577 }
578
579 // Cases, labels, and defaults aren't "scope parents". It's also
580 // important to handle these iteratively instead of recursively in
581 // order to avoid blowing out the stack.
582 while (true) {
583 Stmt *Next;
584 if (SwitchCase *SC = dyn_cast<SwitchCase>(SubStmt))
585 Next = SC->getSubStmt();
586 else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt))
587 Next = LS->getSubStmt();
588 else
589 break;
590
591 LabelAndGotoScopes[SubStmt] = ParentScope;
592 SubStmt = Next;
593 }
594
595 // Recursively walk the AST.
596 BuildScopeInformation(SubStmt, ParentScope);
597 }
598 }
599
600 /// VerifyJumps - Verify each element of the Jumps array to see if they are
601 /// valid, emitting diagnostics if not.
VerifyJumps()602 void JumpScopeChecker::VerifyJumps() {
603 while (!Jumps.empty()) {
604 Stmt *Jump = Jumps.pop_back_val();
605
606 // With a goto,
607 if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {
608 // The label may not have a statement if it's coming from inline MS ASM.
609 if (GS->getLabel()->getStmt()) {
610 CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),
611 diag::err_goto_into_protected_scope,
612 diag::ext_goto_into_protected_scope,
613 diag::warn_cxx98_compat_goto_into_protected_scope);
614 }
615 CheckGotoStmt(GS);
616 continue;
617 }
618
619 // We only get indirect gotos here when they have a constant target.
620 if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Jump)) {
621 LabelDecl *Target = IGS->getConstantTarget();
622 CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(),
623 diag::err_goto_into_protected_scope,
624 diag::ext_goto_into_protected_scope,
625 diag::warn_cxx98_compat_goto_into_protected_scope);
626 continue;
627 }
628
629 SwitchStmt *SS = cast<SwitchStmt>(Jump);
630 for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
631 SC = SC->getNextSwitchCase()) {
632 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC)))
633 continue;
634 SourceLocation Loc;
635 if (CaseStmt *CS = dyn_cast<CaseStmt>(SC))
636 Loc = CS->getBeginLoc();
637 else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC))
638 Loc = DS->getBeginLoc();
639 else
640 Loc = SC->getBeginLoc();
641 CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,
642 diag::warn_cxx98_compat_switch_into_protected_scope);
643 }
644 }
645 }
646
647 /// VerifyIndirectOrAsmJumps - Verify whether any possible indirect goto or
648 /// asm goto jump might cross a protection boundary. Unlike direct jumps,
649 /// indirect or asm goto jumps count cleanups as protection boundaries:
650 /// since there's no way to know where the jump is going, we can't implicitly
651 /// run the right cleanups the way we can with direct jumps.
652 /// Thus, an indirect/asm jump is "trivial" if it bypasses no
653 /// initializations and no teardowns. More formally, an indirect/asm jump
654 /// from A to B is trivial if the path out from A to DCA(A,B) is
655 /// trivial and the path in from DCA(A,B) to B is trivial, where
656 /// DCA(A,B) is the deepest common ancestor of A and B.
657 /// Jump-triviality is transitive but asymmetric.
658 ///
659 /// A path in is trivial if none of the entered scopes have an InDiag.
660 /// A path out is trivial is none of the exited scopes have an OutDiag.
661 ///
662 /// Under these definitions, this function checks that the indirect
663 /// jump between A and B is trivial for every indirect goto statement A
664 /// and every label B whose address was taken in the function.
VerifyIndirectOrAsmJumps(bool IsAsmGoto)665 void JumpScopeChecker::VerifyIndirectOrAsmJumps(bool IsAsmGoto) {
666 SmallVector<Stmt*, 4> GotoJumps = IsAsmGoto ? AsmJumps : IndirectJumps;
667 if (GotoJumps.empty())
668 return;
669 SmallVector<LabelDecl *, 4> JumpTargets =
670 IsAsmGoto ? AsmJumpTargets : IndirectJumpTargets;
671 // If there aren't any address-of-label expressions in this function,
672 // complain about the first indirect goto.
673 if (JumpTargets.empty()) {
674 assert(!IsAsmGoto &&"only indirect goto can get here");
675 S.Diag(GotoJumps[0]->getBeginLoc(),
676 diag::err_indirect_goto_without_addrlabel);
677 return;
678 }
679 // Collect a single representative of every scope containing an
680 // indirect or asm goto. For most code bases, this substantially cuts
681 // down on the number of jump sites we'll have to consider later.
682 typedef std::pair<unsigned, Stmt*> JumpScope;
683 SmallVector<JumpScope, 32> JumpScopes;
684 {
685 llvm::DenseMap<unsigned, Stmt*> JumpScopesMap;
686 for (SmallVectorImpl<Stmt *>::iterator I = GotoJumps.begin(),
687 E = GotoJumps.end();
688 I != E; ++I) {
689 Stmt *IG = *I;
690 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG)))
691 continue;
692 unsigned IGScope = LabelAndGotoScopes[IG];
693 Stmt *&Entry = JumpScopesMap[IGScope];
694 if (!Entry) Entry = IG;
695 }
696 JumpScopes.reserve(JumpScopesMap.size());
697 for (llvm::DenseMap<unsigned, Stmt *>::iterator I = JumpScopesMap.begin(),
698 E = JumpScopesMap.end();
699 I != E; ++I)
700 JumpScopes.push_back(*I);
701 }
702
703 // Collect a single representative of every scope containing a
704 // label whose address was taken somewhere in the function.
705 // For most code bases, there will be only one such scope.
706 llvm::DenseMap<unsigned, LabelDecl*> TargetScopes;
707 for (SmallVectorImpl<LabelDecl *>::iterator I = JumpTargets.begin(),
708 E = JumpTargets.end();
709 I != E; ++I) {
710 LabelDecl *TheLabel = *I;
711 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt())))
712 continue;
713 unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()];
714 LabelDecl *&Target = TargetScopes[LabelScope];
715 if (!Target) Target = TheLabel;
716 }
717
718 // For each target scope, make sure it's trivially reachable from
719 // every scope containing a jump site.
720 //
721 // A path between scopes always consists of exitting zero or more
722 // scopes, then entering zero or more scopes. We build a set of
723 // of scopes S from which the target scope can be trivially
724 // entered, then verify that every jump scope can be trivially
725 // exitted to reach a scope in S.
726 llvm::BitVector Reachable(Scopes.size(), false);
727 for (llvm::DenseMap<unsigned,LabelDecl*>::iterator
728 TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) {
729 unsigned TargetScope = TI->first;
730 LabelDecl *TargetLabel = TI->second;
731
732 Reachable.reset();
733
734 // Mark all the enclosing scopes from which you can safely jump
735 // into the target scope. 'Min' will end up being the index of
736 // the shallowest such scope.
737 unsigned Min = TargetScope;
738 while (true) {
739 Reachable.set(Min);
740
741 // Don't go beyond the outermost scope.
742 if (Min == 0) break;
743
744 // Stop if we can't trivially enter the current scope.
745 if (Scopes[Min].InDiag) break;
746
747 Min = Scopes[Min].ParentScope;
748 }
749
750 // Walk through all the jump sites, checking that they can trivially
751 // reach this label scope.
752 for (SmallVectorImpl<JumpScope>::iterator
753 I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) {
754 unsigned Scope = I->first;
755
756 // Walk out the "scope chain" for this scope, looking for a scope
757 // we've marked reachable. For well-formed code this amortizes
758 // to O(JumpScopes.size() / Scopes.size()): we only iterate
759 // when we see something unmarked, and in well-formed code we
760 // mark everything we iterate past.
761 bool IsReachable = false;
762 while (true) {
763 if (Reachable.test(Scope)) {
764 // If we find something reachable, mark all the scopes we just
765 // walked through as reachable.
766 for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope)
767 Reachable.set(S);
768 IsReachable = true;
769 break;
770 }
771
772 // Don't walk out if we've reached the top-level scope or we've
773 // gotten shallower than the shallowest reachable scope.
774 if (Scope == 0 || Scope < Min) break;
775
776 // Don't walk out through an out-diagnostic.
777 if (Scopes[Scope].OutDiag) break;
778
779 Scope = Scopes[Scope].ParentScope;
780 }
781
782 // Only diagnose if we didn't find something.
783 if (IsReachable) continue;
784
785 DiagnoseIndirectOrAsmJump(I->second, I->first, TargetLabel, TargetScope);
786 }
787 }
788 }
789
790 /// Return true if a particular error+note combination must be downgraded to a
791 /// warning in Microsoft mode.
IsMicrosoftJumpWarning(unsigned JumpDiag,unsigned InDiagNote)792 static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) {
793 return (JumpDiag == diag::err_goto_into_protected_scope &&
794 (InDiagNote == diag::note_protected_by_variable_init ||
795 InDiagNote == diag::note_protected_by_variable_nontriv_destructor));
796 }
797
798 /// Return true if a particular note should be downgraded to a compatibility
799 /// warning in C++11 mode.
IsCXX98CompatWarning(Sema & S,unsigned InDiagNote)800 static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) {
801 return S.getLangOpts().CPlusPlus11 &&
802 InDiagNote == diag::note_protected_by_variable_non_pod;
803 }
804
805 /// Produce primary diagnostic for an indirect jump statement.
DiagnoseIndirectOrAsmJumpStmt(Sema & S,Stmt * Jump,LabelDecl * Target,bool & Diagnosed)806 static void DiagnoseIndirectOrAsmJumpStmt(Sema &S, Stmt *Jump,
807 LabelDecl *Target, bool &Diagnosed) {
808 if (Diagnosed)
809 return;
810 bool IsAsmGoto = isa<GCCAsmStmt>(Jump);
811 S.Diag(Jump->getBeginLoc(), diag::err_indirect_goto_in_protected_scope)
812 << IsAsmGoto;
813 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
814 << IsAsmGoto;
815 Diagnosed = true;
816 }
817
818 /// Produce note diagnostics for a jump into a protected scope.
NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes)819 void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {
820 if (CHECK_PERMISSIVE(ToScopes.empty()))
821 return;
822 for (unsigned I = 0, E = ToScopes.size(); I != E; ++I)
823 if (Scopes[ToScopes[I]].InDiag)
824 S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag);
825 }
826
827 /// Diagnose an indirect jump which is known to cross scopes.
DiagnoseIndirectOrAsmJump(Stmt * Jump,unsigned JumpScope,LabelDecl * Target,unsigned TargetScope)828 void JumpScopeChecker::DiagnoseIndirectOrAsmJump(Stmt *Jump, unsigned JumpScope,
829 LabelDecl *Target,
830 unsigned TargetScope) {
831 if (CHECK_PERMISSIVE(JumpScope == TargetScope))
832 return;
833
834 unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope);
835 bool Diagnosed = false;
836
837 // Walk out the scope chain until we reach the common ancestor.
838 for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope)
839 if (Scopes[I].OutDiag) {
840 DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed);
841 S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);
842 }
843
844 SmallVector<unsigned, 10> ToScopesCXX98Compat;
845
846 // Now walk into the scopes containing the label whose address was taken.
847 for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope)
848 if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
849 ToScopesCXX98Compat.push_back(I);
850 else if (Scopes[I].InDiag) {
851 DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed);
852 S.Diag(Scopes[I].Loc, Scopes[I].InDiag);
853 }
854
855 // Diagnose this jump if it would be ill-formed in C++98.
856 if (!Diagnosed && !ToScopesCXX98Compat.empty()) {
857 bool IsAsmGoto = isa<GCCAsmStmt>(Jump);
858 S.Diag(Jump->getBeginLoc(),
859 diag::warn_cxx98_compat_indirect_goto_in_protected_scope)
860 << IsAsmGoto;
861 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
862 << IsAsmGoto;
863 NoteJumpIntoScopes(ToScopesCXX98Compat);
864 }
865 }
866
867 /// CheckJump - Validate that the specified jump statement is valid: that it is
868 /// jumping within or out of its current scope, not into a deeper one.
CheckJump(Stmt * From,Stmt * To,SourceLocation DiagLoc,unsigned JumpDiagError,unsigned JumpDiagWarning,unsigned JumpDiagCXX98Compat)869 void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
870 unsigned JumpDiagError, unsigned JumpDiagWarning,
871 unsigned JumpDiagCXX98Compat) {
872 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(From)))
873 return;
874 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To)))
875 return;
876
877 unsigned FromScope = LabelAndGotoScopes[From];
878 unsigned ToScope = LabelAndGotoScopes[To];
879
880 // Common case: exactly the same scope, which is fine.
881 if (FromScope == ToScope) return;
882
883 // Warn on gotos out of __finally blocks.
884 if (isa<GotoStmt>(From) || isa<IndirectGotoStmt>(From)) {
885 // If FromScope > ToScope, FromScope is more nested and the jump goes to a
886 // less nested scope. Check if it crosses a __finally along the way.
887 for (unsigned I = FromScope; I > ToScope; I = Scopes[I].ParentScope) {
888 if (Scopes[I].InDiag == diag::note_protected_by_seh_finally) {
889 S.Diag(From->getBeginLoc(), diag::warn_jump_out_of_seh_finally);
890 break;
891 }
892 }
893 }
894
895 unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope);
896
897 // It's okay to jump out from a nested scope.
898 if (CommonScope == ToScope) return;
899
900 // Pull out (and reverse) any scopes we might need to diagnose skipping.
901 SmallVector<unsigned, 10> ToScopesCXX98Compat;
902 SmallVector<unsigned, 10> ToScopesError;
903 SmallVector<unsigned, 10> ToScopesWarning;
904 for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) {
905 if (S.getLangOpts().MSVCCompat && JumpDiagWarning != 0 &&
906 IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag))
907 ToScopesWarning.push_back(I);
908 else if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
909 ToScopesCXX98Compat.push_back(I);
910 else if (Scopes[I].InDiag)
911 ToScopesError.push_back(I);
912 }
913
914 // Handle warnings.
915 if (!ToScopesWarning.empty()) {
916 S.Diag(DiagLoc, JumpDiagWarning);
917 NoteJumpIntoScopes(ToScopesWarning);
918 }
919
920 // Handle errors.
921 if (!ToScopesError.empty()) {
922 S.Diag(DiagLoc, JumpDiagError);
923 NoteJumpIntoScopes(ToScopesError);
924 }
925
926 // Handle -Wc++98-compat warnings if the jump is well-formed.
927 if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) {
928 S.Diag(DiagLoc, JumpDiagCXX98Compat);
929 NoteJumpIntoScopes(ToScopesCXX98Compat);
930 }
931 }
932
CheckGotoStmt(GotoStmt * GS)933 void JumpScopeChecker::CheckGotoStmt(GotoStmt *GS) {
934 if (GS->getLabel()->isMSAsmLabel()) {
935 S.Diag(GS->getGotoLoc(), diag::err_goto_ms_asm_label)
936 << GS->getLabel()->getIdentifier();
937 S.Diag(GS->getLabel()->getLocation(), diag::note_goto_ms_asm_label)
938 << GS->getLabel()->getIdentifier();
939 }
940 }
941
DiagnoseInvalidJumps(Stmt * Body)942 void Sema::DiagnoseInvalidJumps(Stmt *Body) {
943 (void)JumpScopeChecker(Body, *this);
944 }
945