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/AST/DeclCXX.h"
15#include "clang/AST/Expr.h"
16#include "clang/AST/ExprCXX.h"
17#include "clang/AST/StmtCXX.h"
18#include "clang/AST/StmtObjC.h"
19#include "clang/AST/StmtOpenACC.h"
20#include "clang/AST/StmtOpenMP.h"
21#include "clang/Basic/SourceLocation.h"
22#include "clang/Sema/SemaInternal.h"
23#include "llvm/ADT/BitVector.h"
24using namespace clang;
25
26namespace {
27
28/// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps
29/// into VLA and other protected scopes. For example, this rejects:
30/// goto L;
31/// int a[n];
32/// L:
33///
34/// We also detect jumps out of protected scopes when it's not possible to do
35/// cleanups properly. Indirect jumps and ASM jumps can't do cleanups because
36/// the target is unknown. Return statements with \c [[clang::musttail]] cannot
37/// handle any cleanups due to the nature of a tail call.
38class JumpScopeChecker {
39 Sema &S;
40
41 /// Permissive - True when recovering from errors, in which case precautions
42 /// are taken to handle incomplete scope information.
43 const bool Permissive;
44
45 /// GotoScope - This is a record that we use to keep track of all of the
46 /// scopes that are introduced by VLAs and other things that scope jumps like
47 /// gotos. This scope tree has nothing to do with the source scope tree,
48 /// because you can have multiple VLA scopes per compound statement, and most
49 /// compound statements don't introduce any scopes.
50 struct GotoScope {
51 /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
52 /// the parent scope is the function body.
53 unsigned ParentScope;
54
55 /// InDiag - The note to emit if there is a jump into this scope.
56 unsigned InDiag;
57
58 /// OutDiag - The note to emit if there is an indirect jump out
59 /// of this scope. Direct jumps always clean up their current scope
60 /// in an orderly way.
61 unsigned OutDiag;
62
63 /// Loc - Location to emit the diagnostic.
64 SourceLocation Loc;
65
66 GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag,
67 SourceLocation L)
68 : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {}
69 };
70
71 SmallVector<GotoScope, 48> Scopes;
72 llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
73 SmallVector<Stmt*, 16> Jumps;
74
75 SmallVector<Stmt*, 4> IndirectJumps;
76 SmallVector<LabelDecl *, 4> IndirectJumpTargets;
77 SmallVector<AttributedStmt *, 4> MustTailStmts;
78
79public:
80 JumpScopeChecker(Stmt *Body, Sema &S);
81private:
82 void BuildScopeInformation(Decl *D, unsigned &ParentScope);
83 void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,
84 unsigned &ParentScope);
85 void BuildScopeInformation(CompoundLiteralExpr *CLE, unsigned &ParentScope);
86 void BuildScopeInformation(Stmt *S, unsigned &origParentScope);
87
88 void VerifyJumps();
89 void VerifyIndirectJumps();
90 void VerifyMustTailStmts();
91 void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);
92 void DiagnoseIndirectOrAsmJump(Stmt *IG, unsigned IGScope, LabelDecl *Target,
93 unsigned TargetScope);
94 void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
95 unsigned JumpDiag, unsigned JumpDiagWarning,
96 unsigned JumpDiagCompat);
97 void CheckGotoStmt(GotoStmt *GS);
98 const Attr *GetMustTailAttr(AttributedStmt *AS);
99
100 unsigned GetDeepestCommonScope(unsigned A, unsigned B);
101};
102} // end anonymous namespace
103
104#define CHECK_PERMISSIVE(x) (assert(Permissive || !(x)), (Permissive && (x)))
105
106JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s)
107 : S(s), Permissive(s.hasAnyUnrecoverableErrorsInThisFunction()) {
108 // Add a scope entry for function scope.
109 Scopes.push_back(Elt: GotoScope(~0U, ~0U, ~0U, SourceLocation()));
110
111 // Build information for the top level compound statement, so that we have a
112 // defined scope record for every "goto" and label.
113 unsigned BodyParentScope = 0;
114 BuildScopeInformation(S: Body, origParentScope&: BodyParentScope);
115
116 // Check that all jumps we saw are kosher.
117 VerifyJumps();
118 VerifyIndirectJumps();
119 VerifyMustTailStmts();
120}
121
122/// GetDeepestCommonScope - Finds the innermost scope enclosing the
123/// two scopes.
124unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) {
125 while (A != B) {
126 // Inner scopes are created after outer scopes and therefore have
127 // higher indices.
128 if (A < B) {
129 assert(Scopes[B].ParentScope < B);
130 B = Scopes[B].ParentScope;
131 } else {
132 assert(Scopes[A].ParentScope < A);
133 A = Scopes[A].ParentScope;
134 }
135 }
136 return A;
137}
138
139typedef std::pair<unsigned,unsigned> ScopePair;
140
141/// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
142/// diagnostic that should be emitted if control goes over it. If not, return 0.
143static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D) {
144 if (const VarDecl *VD = dyn_cast<VarDecl>(Val: D)) {
145 unsigned InDiag = 0;
146 unsigned OutDiag = 0;
147
148 if (VD->getType()->isVariablyModifiedType())
149 InDiag = diag::note_protected_by_vla;
150
151 if (VD->hasAttr<BlocksAttr>())
152 return ScopePair(diag::note_protected_by___block,
153 diag::note_exits___block);
154
155 if (VD->hasAttr<CleanupAttr>())
156 return ScopePair(diag::note_protected_by_cleanup,
157 diag::note_exits_cleanup);
158
159 if (VD->hasLocalStorage()) {
160 switch (VD->getType().isDestructedType()) {
161 case QualType::DK_objc_strong_lifetime:
162 return ScopePair(diag::note_protected_by_objc_strong_init,
163 diag::note_exits_objc_strong);
164
165 case QualType::DK_objc_weak_lifetime:
166 return ScopePair(diag::note_protected_by_objc_weak_init,
167 diag::note_exits_objc_weak);
168
169 case QualType::DK_nontrivial_c_struct:
170 return ScopePair(diag::note_protected_by_non_trivial_c_struct_init,
171 diag::note_exits_dtor);
172
173 case QualType::DK_cxx_destructor:
174 OutDiag = diag::note_exits_dtor;
175 break;
176
177 case QualType::DK_none:
178 break;
179 }
180 }
181
182 if (const Expr *Init = VD->getInit();
183 VD->hasLocalStorage() && Init && !Init->containsErrors()) {
184 // C++11 [stmt.dcl]p3:
185 // A program that jumps from a point where a variable with automatic
186 // storage duration is not in scope to a point where it is in scope
187 // is ill-formed unless the variable has scalar type, class type with
188 // a trivial default constructor and a trivial destructor, a
189 // cv-qualified version of one of these types, or an array of one of
190 // the preceding types and is declared without an initializer.
191
192 // C++03 [stmt.dcl.p3:
193 // A program that jumps from a point where a local variable
194 // with automatic storage duration is not in scope to a point
195 // where it is in scope is ill-formed unless the variable has
196 // POD type and is declared without an initializer.
197
198 InDiag = diag::note_protected_by_variable_init;
199
200 // For a variable of (array of) class type declared without an
201 // initializer, we will have call-style initialization and the initializer
202 // will be the CXXConstructExpr with no intervening nodes.
203 if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Val: Init)) {
204 const CXXConstructorDecl *Ctor = CCE->getConstructor();
205 if (Ctor->isTrivial() && Ctor->isDefaultConstructor() &&
206 VD->getInitStyle() == VarDecl::CallInit) {
207 if (OutDiag)
208 InDiag = diag::note_protected_by_variable_nontriv_destructor;
209 else if (!Ctor->getParent()->isPOD())
210 InDiag = diag::note_protected_by_variable_non_pod;
211 else
212 InDiag = 0;
213 }
214 }
215 }
216
217 return ScopePair(InDiag, OutDiag);
218 }
219
220 if (const TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(Val: D)) {
221 if (TD->getUnderlyingType()->isVariablyModifiedType())
222 return ScopePair(isa<TypedefDecl>(TD)
223 ? diag::note_protected_by_vla_typedef
224 : diag::note_protected_by_vla_type_alias,
225 0);
226 }
227
228 return ScopePair(0U, 0U);
229}
230
231/// Build scope information for a declaration that is part of a DeclStmt.
232void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) {
233 // If this decl causes a new scope, push and switch to it.
234 std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S, D);
235 if (Diags.first || Diags.second) {
236 Scopes.push_back(Elt: GotoScope(ParentScope, Diags.first, Diags.second,
237 D->getLocation()));
238 ParentScope = Scopes.size()-1;
239 }
240
241 // If the decl has an initializer, walk it with the potentially new
242 // scope we just installed.
243 if (VarDecl *VD = dyn_cast<VarDecl>(Val: D))
244 if (Expr *Init = VD->getInit())
245 BuildScopeInformation(Init, ParentScope);
246}
247
248/// Build scope information for a captured block literal variables.
249void JumpScopeChecker::BuildScopeInformation(VarDecl *D,
250 const BlockDecl *BDecl,
251 unsigned &ParentScope) {
252 // exclude captured __block variables; there's no destructor
253 // associated with the block literal for them.
254 if (D->hasAttr<BlocksAttr>())
255 return;
256 QualType T = D->getType();
257 QualType::DestructionKind destructKind = T.isDestructedType();
258 if (destructKind != QualType::DK_none) {
259 std::pair<unsigned,unsigned> Diags;
260 switch (destructKind) {
261 case QualType::DK_cxx_destructor:
262 Diags = ScopePair(diag::note_enters_block_captures_cxx_obj,
263 diag::note_exits_block_captures_cxx_obj);
264 break;
265 case QualType::DK_objc_strong_lifetime:
266 Diags = ScopePair(diag::note_enters_block_captures_strong,
267 diag::note_exits_block_captures_strong);
268 break;
269 case QualType::DK_objc_weak_lifetime:
270 Diags = ScopePair(diag::note_enters_block_captures_weak,
271 diag::note_exits_block_captures_weak);
272 break;
273 case QualType::DK_nontrivial_c_struct:
274 Diags = ScopePair(diag::note_enters_block_captures_non_trivial_c_struct,
275 diag::note_exits_block_captures_non_trivial_c_struct);
276 break;
277 case QualType::DK_none:
278 llvm_unreachable("non-lifetime captured variable");
279 }
280 SourceLocation Loc = D->getLocation();
281 if (Loc.isInvalid())
282 Loc = BDecl->getLocation();
283 Scopes.push_back(Elt: GotoScope(ParentScope,
284 Diags.first, Diags.second, Loc));
285 ParentScope = Scopes.size()-1;
286 }
287}
288
289/// Build scope information for compound literals of C struct types that are
290/// non-trivial to destruct.
291void JumpScopeChecker::BuildScopeInformation(CompoundLiteralExpr *CLE,
292 unsigned &ParentScope) {
293 unsigned InDiag = diag::note_enters_compound_literal_scope;
294 unsigned OutDiag = diag::note_exits_compound_literal_scope;
295 Scopes.push_back(Elt: GotoScope(ParentScope, InDiag, OutDiag, CLE->getExprLoc()));
296 ParentScope = Scopes.size() - 1;
297}
298
299/// BuildScopeInformation - The statements from CI to CE are known to form a
300/// coherent VLA scope with a specified parent node. Walk through the
301/// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
302/// walking the AST as needed.
303void JumpScopeChecker::BuildScopeInformation(Stmt *S,
304 unsigned &origParentScope) {
305 // If this is a statement, rather than an expression, scopes within it don't
306 // propagate out into the enclosing scope. Otherwise we have to worry
307 // about block literals, which have the lifetime of their enclosing statement.
308 unsigned independentParentScope = origParentScope;
309 unsigned &ParentScope = ((isa<Expr>(Val: S) && !isa<StmtExpr>(Val: S))
310 ? origParentScope : independentParentScope);
311
312 unsigned StmtsToSkip = 0u;
313
314 // If we found a label, remember that it is in ParentScope scope.
315 switch (S->getStmtClass()) {
316 case Stmt::AddrLabelExprClass:
317 IndirectJumpTargets.push_back(Elt: cast<AddrLabelExpr>(Val: S)->getLabel());
318 break;
319
320 case Stmt::ObjCForCollectionStmtClass: {
321 auto *CS = cast<ObjCForCollectionStmt>(Val: S);
322 unsigned Diag = diag::note_protected_by_objc_fast_enumeration;
323 unsigned NewParentScope = Scopes.size();
324 Scopes.push_back(Elt: GotoScope(ParentScope, Diag, 0, S->getBeginLoc()));
325 BuildScopeInformation(S: CS->getBody(), origParentScope&: NewParentScope);
326 return;
327 }
328
329 case Stmt::IndirectGotoStmtClass:
330 // "goto *&&lbl;" is a special case which we treat as equivalent
331 // to a normal goto. In addition, we don't calculate scope in the
332 // operand (to avoid recording the address-of-label use), which
333 // works only because of the restricted set of expressions which
334 // we detect as constant targets.
335 if (cast<IndirectGotoStmt>(Val: S)->getConstantTarget())
336 goto RecordJumpScope;
337
338 LabelAndGotoScopes[S] = ParentScope;
339 IndirectJumps.push_back(Elt: S);
340 break;
341
342 case Stmt::SwitchStmtClass:
343 // Evaluate the C++17 init stmt and condition variable
344 // before entering the scope of the switch statement.
345 if (Stmt *Init = cast<SwitchStmt>(Val: S)->getInit()) {
346 BuildScopeInformation(S: Init, origParentScope&: ParentScope);
347 ++StmtsToSkip;
348 }
349 if (VarDecl *Var = cast<SwitchStmt>(Val: S)->getConditionVariable()) {
350 BuildScopeInformation(Var, ParentScope);
351 ++StmtsToSkip;
352 }
353 goto RecordJumpScope;
354
355 case Stmt::GCCAsmStmtClass:
356 if (!cast<GCCAsmStmt>(Val: S)->isAsmGoto())
357 break;
358 [[fallthrough]];
359
360 case Stmt::GotoStmtClass:
361 RecordJumpScope:
362 // Remember both what scope a goto is in as well as the fact that we have
363 // it. This makes the second scan not have to walk the AST again.
364 LabelAndGotoScopes[S] = ParentScope;
365 Jumps.push_back(Elt: S);
366 break;
367
368 case Stmt::IfStmtClass: {
369 IfStmt *IS = cast<IfStmt>(Val: S);
370 if (!(IS->isConstexpr() || IS->isConsteval() ||
371 IS->isObjCAvailabilityCheck()))
372 break;
373
374 unsigned Diag = diag::note_protected_by_if_available;
375 if (IS->isConstexpr())
376 Diag = diag::note_protected_by_constexpr_if;
377 else if (IS->isConsteval())
378 Diag = diag::note_protected_by_consteval_if;
379
380 if (VarDecl *Var = IS->getConditionVariable())
381 BuildScopeInformation(Var, ParentScope);
382
383 // Cannot jump into the middle of the condition.
384 unsigned NewParentScope = Scopes.size();
385 Scopes.push_back(Elt: GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
386
387 if (!IS->isConsteval())
388 BuildScopeInformation(IS->getCond(), NewParentScope);
389
390 // Jumps into either arm of an 'if constexpr' are not allowed.
391 NewParentScope = Scopes.size();
392 Scopes.push_back(Elt: GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
393 BuildScopeInformation(S: IS->getThen(), origParentScope&: NewParentScope);
394 if (Stmt *Else = IS->getElse()) {
395 NewParentScope = Scopes.size();
396 Scopes.push_back(Elt: GotoScope(ParentScope, Diag, 0, IS->getBeginLoc()));
397 BuildScopeInformation(S: Else, origParentScope&: NewParentScope);
398 }
399 return;
400 }
401
402 case Stmt::CXXTryStmtClass: {
403 CXXTryStmt *TS = cast<CXXTryStmt>(Val: S);
404 {
405 unsigned NewParentScope = Scopes.size();
406 Scopes.push_back(GotoScope(ParentScope,
407 diag::note_protected_by_cxx_try,
408 diag::note_exits_cxx_try,
409 TS->getSourceRange().getBegin()));
410 if (Stmt *TryBlock = TS->getTryBlock())
411 BuildScopeInformation(S: TryBlock, origParentScope&: NewParentScope);
412 }
413
414 // Jump from the catch into the try is not allowed either.
415 for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
416 CXXCatchStmt *CS = TS->getHandler(i: I);
417 unsigned NewParentScope = Scopes.size();
418 Scopes.push_back(GotoScope(ParentScope,
419 diag::note_protected_by_cxx_catch,
420 diag::note_exits_cxx_catch,
421 CS->getSourceRange().getBegin()));
422 BuildScopeInformation(S: CS->getHandlerBlock(), origParentScope&: NewParentScope);
423 }
424 return;
425 }
426
427 case Stmt::SEHTryStmtClass: {
428 SEHTryStmt *TS = cast<SEHTryStmt>(Val: S);
429 {
430 unsigned NewParentScope = Scopes.size();
431 Scopes.push_back(GotoScope(ParentScope,
432 diag::note_protected_by_seh_try,
433 diag::note_exits_seh_try,
434 TS->getSourceRange().getBegin()));
435 if (Stmt *TryBlock = TS->getTryBlock())
436 BuildScopeInformation(S: TryBlock, origParentScope&: NewParentScope);
437 }
438
439 // Jump from __except or __finally into the __try are not allowed either.
440 if (SEHExceptStmt *Except = TS->getExceptHandler()) {
441 unsigned NewParentScope = Scopes.size();
442 Scopes.push_back(GotoScope(ParentScope,
443 diag::note_protected_by_seh_except,
444 diag::note_exits_seh_except,
445 Except->getSourceRange().getBegin()));
446 BuildScopeInformation(Except->getBlock(), NewParentScope);
447 } else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) {
448 unsigned NewParentScope = Scopes.size();
449 Scopes.push_back(GotoScope(ParentScope,
450 diag::note_protected_by_seh_finally,
451 diag::note_exits_seh_finally,
452 Finally->getSourceRange().getBegin()));
453 BuildScopeInformation(Finally->getBlock(), NewParentScope);
454 }
455
456 return;
457 }
458
459 case Stmt::DeclStmtClass: {
460 // If this is a declstmt with a VLA definition, it defines a scope from here
461 // to the end of the containing context.
462 DeclStmt *DS = cast<DeclStmt>(Val: S);
463 // The decl statement creates a scope if any of the decls in it are VLAs
464 // or have the cleanup attribute.
465 for (auto *I : DS->decls())
466 BuildScopeInformation(D: I, ParentScope&: origParentScope);
467 return;
468 }
469
470 case Stmt::StmtExprClass: {
471 // [GNU]
472 // Jumping into a statement expression with goto or using
473 // a switch statement outside the statement expression with
474 // a case or default label inside the statement expression is not permitted.
475 // Jumping out of a statement expression is permitted.
476 StmtExpr *SE = cast<StmtExpr>(Val: S);
477 unsigned NewParentScope = Scopes.size();
478 Scopes.push_back(GotoScope(ParentScope,
479 diag::note_enters_statement_expression,
480 /*OutDiag=*/0, SE->getBeginLoc()));
481 BuildScopeInformation(SE->getSubStmt(), NewParentScope);
482 return;
483 }
484
485 case Stmt::ObjCAtTryStmtClass: {
486 // Disallow jumps into any part of an @try statement by pushing a scope and
487 // walking all sub-stmts in that scope.
488 ObjCAtTryStmt *AT = cast<ObjCAtTryStmt>(Val: S);
489 // Recursively walk the AST for the @try part.
490 {
491 unsigned NewParentScope = Scopes.size();
492 Scopes.push_back(GotoScope(ParentScope,
493 diag::note_protected_by_objc_try,
494 diag::note_exits_objc_try,
495 AT->getAtTryLoc()));
496 if (Stmt *TryPart = AT->getTryBody())
497 BuildScopeInformation(S: TryPart, origParentScope&: NewParentScope);
498 }
499
500 // Jump from the catch to the finally or try is not valid.
501 for (ObjCAtCatchStmt *AC : AT->catch_stmts()) {
502 unsigned NewParentScope = Scopes.size();
503 Scopes.push_back(GotoScope(ParentScope,
504 diag::note_protected_by_objc_catch,
505 diag::note_exits_objc_catch,
506 AC->getAtCatchLoc()));
507 // @catches are nested and it isn't
508 BuildScopeInformation(AC->getCatchBody(), NewParentScope);
509 }
510
511 // Jump from the finally to the try or catch is not valid.
512 if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
513 unsigned NewParentScope = Scopes.size();
514 Scopes.push_back(GotoScope(ParentScope,
515 diag::note_protected_by_objc_finally,
516 diag::note_exits_objc_finally,
517 AF->getAtFinallyLoc()));
518 BuildScopeInformation(S: AF, origParentScope&: NewParentScope);
519 }
520
521 return;
522 }
523
524 case Stmt::ObjCAtSynchronizedStmtClass: {
525 // Disallow jumps into the protected statement of an @synchronized, but
526 // allow jumps into the object expression it protects.
527 ObjCAtSynchronizedStmt *AS = cast<ObjCAtSynchronizedStmt>(Val: S);
528 // Recursively walk the AST for the @synchronized object expr, it is
529 // evaluated in the normal scope.
530 BuildScopeInformation(AS->getSynchExpr(), ParentScope);
531
532 // Recursively walk the AST for the @synchronized part, protected by a new
533 // scope.
534 unsigned NewParentScope = Scopes.size();
535 Scopes.push_back(GotoScope(ParentScope,
536 diag::note_protected_by_objc_synchronized,
537 diag::note_exits_objc_synchronized,
538 AS->getAtSynchronizedLoc()));
539 BuildScopeInformation(AS->getSynchBody(), NewParentScope);
540 return;
541 }
542
543 case Stmt::ObjCAutoreleasePoolStmtClass: {
544 // Disallow jumps into the protected statement of an @autoreleasepool.
545 ObjCAutoreleasePoolStmt *AS = cast<ObjCAutoreleasePoolStmt>(Val: S);
546 // Recursively walk the AST for the @autoreleasepool part, protected by a
547 // new scope.
548 unsigned NewParentScope = Scopes.size();
549 Scopes.push_back(GotoScope(ParentScope,
550 diag::note_protected_by_objc_autoreleasepool,
551 diag::note_exits_objc_autoreleasepool,
552 AS->getAtLoc()));
553 BuildScopeInformation(S: AS->getSubStmt(), origParentScope&: NewParentScope);
554 return;
555 }
556
557 case Stmt::ExprWithCleanupsClass: {
558 // Disallow jumps past full-expressions that use blocks with
559 // non-trivial cleanups of their captures. This is theoretically
560 // implementable but a lot of work which we haven't felt up to doing.
561 ExprWithCleanups *EWC = cast<ExprWithCleanups>(Val: S);
562 for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) {
563 if (auto *BDecl = dyn_cast<BlockDecl *>(Val: EWC->getObject(i)))
564 for (const auto &CI : BDecl->captures()) {
565 VarDecl *variable = CI.getVariable();
566 BuildScopeInformation(D: variable, BDecl, ParentScope&: origParentScope);
567 }
568 else if (auto *CLE = dyn_cast<CompoundLiteralExpr *>(Val: EWC->getObject(i)))
569 BuildScopeInformation(CLE, ParentScope&: origParentScope);
570 else
571 llvm_unreachable("unexpected cleanup object type");
572 }
573 break;
574 }
575
576 case Stmt::MaterializeTemporaryExprClass: {
577 // Disallow jumps out of scopes containing temporaries lifetime-extended to
578 // automatic storage duration.
579 MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(Val: S);
580 if (MTE->getStorageDuration() == SD_Automatic) {
581 const Expr *ExtendedObject =
582 MTE->getSubExpr()->skipRValueSubobjectAdjustments();
583 if (ExtendedObject->getType().isDestructedType()) {
584 Scopes.push_back(GotoScope(ParentScope, 0,
585 diag::note_exits_temporary_dtor,
586 ExtendedObject->getExprLoc()));
587 origParentScope = Scopes.size()-1;
588 }
589 }
590 break;
591 }
592
593 case Stmt::CaseStmtClass:
594 case Stmt::DefaultStmtClass:
595 case Stmt::LabelStmtClass:
596 LabelAndGotoScopes[S] = ParentScope;
597 break;
598
599 case Stmt::OpenACCComputeConstructClass: {
600 unsigned NewParentScope = Scopes.size();
601 OpenACCComputeConstruct *CC = cast<OpenACCComputeConstruct>(Val: S);
602 Scopes.push_back(GotoScope(
603 ParentScope, diag::note_acc_branch_into_compute_construct,
604 diag::note_acc_branch_out_of_compute_construct, CC->getBeginLoc()));
605 // This can be 'null' if the 'body' is a break that we diagnosed, so no
606 // reason to put the scope into place.
607 if (CC->getStructuredBlock())
608 BuildScopeInformation(S: CC->getStructuredBlock(), origParentScope&: NewParentScope);
609 return;
610 }
611
612 case Stmt::OpenACCCombinedConstructClass: {
613 unsigned NewParentScope = Scopes.size();
614 OpenACCCombinedConstruct *CC = cast<OpenACCCombinedConstruct>(Val: S);
615 Scopes.push_back(GotoScope(
616 ParentScope, diag::note_acc_branch_into_compute_construct,
617 diag::note_acc_branch_out_of_compute_construct, CC->getBeginLoc()));
618 // This can be 'null' if the 'body' is a break that we diagnosed, so no
619 // reason to put the scope into place.
620 if (CC->getLoop())
621 BuildScopeInformation(S: CC->getLoop(), origParentScope&: NewParentScope);
622 return;
623 }
624
625 default:
626 if (auto *ED = dyn_cast<OMPExecutableDirective>(Val: S)) {
627 if (!ED->isStandaloneDirective()) {
628 unsigned NewParentScope = Scopes.size();
629 Scopes.emplace_back(ParentScope,
630 diag::note_omp_protected_structured_block,
631 diag::note_omp_exits_structured_block,
632 ED->getStructuredBlock()->getBeginLoc());
633 BuildScopeInformation(S: ED->getStructuredBlock(), origParentScope&: NewParentScope);
634 return;
635 }
636 }
637 break;
638 }
639
640 for (Stmt *SubStmt : S->children()) {
641 if (!SubStmt)
642 continue;
643 if (StmtsToSkip) {
644 --StmtsToSkip;
645 continue;
646 }
647
648 // Cases, labels, attributes, and defaults aren't "scope parents". It's also
649 // important to handle these iteratively instead of recursively in
650 // order to avoid blowing out the stack.
651 while (true) {
652 Stmt *Next;
653 if (SwitchCase *SC = dyn_cast<SwitchCase>(Val: SubStmt))
654 Next = SC->getSubStmt();
655 else if (LabelStmt *LS = dyn_cast<LabelStmt>(Val: SubStmt))
656 Next = LS->getSubStmt();
657 else if (AttributedStmt *AS = dyn_cast<AttributedStmt>(Val: SubStmt)) {
658 if (GetMustTailAttr(AS)) {
659 LabelAndGotoScopes[AS] = ParentScope;
660 MustTailStmts.push_back(Elt: AS);
661 }
662 Next = AS->getSubStmt();
663 } else
664 break;
665
666 LabelAndGotoScopes[SubStmt] = ParentScope;
667 SubStmt = Next;
668 }
669
670 // Recursively walk the AST.
671 BuildScopeInformation(S: SubStmt, origParentScope&: ParentScope);
672 }
673}
674
675/// VerifyJumps - Verify each element of the Jumps array to see if they are
676/// valid, emitting diagnostics if not.
677void JumpScopeChecker::VerifyJumps() {
678 while (!Jumps.empty()) {
679 Stmt *Jump = Jumps.pop_back_val();
680
681 // With a goto,
682 if (GotoStmt *GS = dyn_cast<GotoStmt>(Val: Jump)) {
683 // The label may not have a statement if it's coming from inline MS ASM.
684 if (GS->getLabel()->getStmt()) {
685 CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),
686 diag::err_goto_into_protected_scope,
687 diag::ext_goto_into_protected_scope,
688 S.getLangOpts().CPlusPlus
689 ? diag::warn_cxx98_compat_goto_into_protected_scope
690 : diag::warn_cpp_compat_goto_into_protected_scope);
691 }
692 CheckGotoStmt(GS);
693 continue;
694 }
695
696 // If an asm goto jumps to a different scope, things like destructors or
697 // initializers might not be run which may be suprising to users. Perhaps
698 // this behavior can be changed in the future, but today Clang will not
699 // generate such code. Produce a diagnostic instead. See also the
700 // discussion here: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110728.
701 if (auto *G = dyn_cast<GCCAsmStmt>(Val: Jump)) {
702 for (AddrLabelExpr *L : G->labels()) {
703 LabelDecl *LD = L->getLabel();
704 unsigned JumpScope = LabelAndGotoScopes[G];
705 unsigned TargetScope = LabelAndGotoScopes[LD->getStmt()];
706 if (JumpScope != TargetScope)
707 DiagnoseIndirectOrAsmJump(G, JumpScope, LD, TargetScope);
708 }
709 continue;
710 }
711
712 // We only get indirect gotos here when they have a constant target.
713 if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Val: Jump)) {
714 LabelDecl *Target = IGS->getConstantTarget();
715 CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(),
716 diag::err_goto_into_protected_scope,
717 diag::ext_goto_into_protected_scope,
718 S.getLangOpts().CPlusPlus
719 ? diag::warn_cxx98_compat_goto_into_protected_scope
720 : diag::warn_cpp_compat_goto_into_protected_scope);
721 continue;
722 }
723
724 SwitchStmt *SS = cast<SwitchStmt>(Val: Jump);
725 for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
726 SC = SC->getNextSwitchCase()) {
727 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC)))
728 continue;
729 SourceLocation Loc;
730 if (CaseStmt *CS = dyn_cast<CaseStmt>(Val: SC))
731 Loc = CS->getBeginLoc();
732 else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(Val: SC))
733 Loc = DS->getBeginLoc();
734 else
735 Loc = SC->getBeginLoc();
736 CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,
737 S.getLangOpts().CPlusPlus
738 ? diag::warn_cxx98_compat_switch_into_protected_scope
739 : diag::warn_cpp_compat_switch_into_protected_scope);
740 }
741 }
742}
743
744/// VerifyIndirectJumps - Verify whether any possible indirect goto jump might
745/// cross a protection boundary. Unlike direct jumps, indirect goto jumps
746/// count cleanups as protection boundaries: since there's no way to know where
747/// the jump is going, we can't implicitly run the right cleanups the way we
748/// can with direct jumps. Thus, an indirect/asm jump is "trivial" if it
749/// bypasses no initializations and no teardowns. More formally, an
750/// indirect/asm jump from A to B is trivial if the path out from A to DCA(A,B)
751/// is trivial and the path in from DCA(A,B) to B is trivial, where DCA(A,B) is
752/// the deepest common ancestor of A and B. Jump-triviality is transitive but
753/// asymmetric.
754///
755/// A path in is trivial if none of the entered scopes have an InDiag.
756/// A path out is trivial is none of the exited scopes have an OutDiag.
757///
758/// Under these definitions, this function checks that the indirect
759/// jump between A and B is trivial for every indirect goto statement A
760/// and every label B whose address was taken in the function.
761void JumpScopeChecker::VerifyIndirectJumps() {
762 if (IndirectJumps.empty())
763 return;
764 // If there aren't any address-of-label expressions in this function,
765 // complain about the first indirect goto.
766 if (IndirectJumpTargets.empty()) {
767 S.Diag(IndirectJumps[0]->getBeginLoc(),
768 diag::err_indirect_goto_without_addrlabel);
769 return;
770 }
771 // Collect a single representative of every scope containing an indirect
772 // goto. For most code bases, this substantially cuts down on the number of
773 // jump sites we'll have to consider later.
774 using JumpScope = std::pair<unsigned, Stmt *>;
775 SmallVector<JumpScope, 32> JumpScopes;
776 {
777 llvm::DenseMap<unsigned, Stmt*> JumpScopesMap;
778 for (Stmt *IG : IndirectJumps) {
779 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG)))
780 continue;
781 unsigned IGScope = LabelAndGotoScopes[IG];
782 JumpScopesMap.try_emplace(Key: IGScope, Args&: IG);
783 }
784 JumpScopes.reserve(N: JumpScopesMap.size());
785 for (auto &Pair : JumpScopesMap)
786 JumpScopes.emplace_back(Args&: Pair);
787 }
788
789 // Collect a single representative of every scope containing a
790 // label whose address was taken somewhere in the function.
791 // For most code bases, there will be only one such scope.
792 llvm::DenseMap<unsigned, LabelDecl*> TargetScopes;
793 for (LabelDecl *TheLabel : IndirectJumpTargets) {
794 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt())))
795 continue;
796 unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()];
797 TargetScopes.try_emplace(Key: LabelScope, Args&: TheLabel);
798 }
799
800 // For each target scope, make sure it's trivially reachable from
801 // every scope containing a jump site.
802 //
803 // A path between scopes always consists of exitting zero or more
804 // scopes, then entering zero or more scopes. We build a set of
805 // of scopes S from which the target scope can be trivially
806 // entered, then verify that every jump scope can be trivially
807 // exitted to reach a scope in S.
808 llvm::BitVector Reachable(Scopes.size(), false);
809 for (auto [TargetScope, TargetLabel] : TargetScopes) {
810 Reachable.reset();
811
812 // Mark all the enclosing scopes from which you can safely jump
813 // into the target scope. 'Min' will end up being the index of
814 // the shallowest such scope.
815 unsigned Min = TargetScope;
816 while (true) {
817 Reachable.set(Min);
818
819 // Don't go beyond the outermost scope.
820 if (Min == 0) break;
821
822 // Stop if we can't trivially enter the current scope.
823 if (Scopes[Min].InDiag) break;
824
825 Min = Scopes[Min].ParentScope;
826 }
827
828 // Walk through all the jump sites, checking that they can trivially
829 // reach this label scope.
830 for (auto [JumpScope, JumpStmt] : JumpScopes) {
831 unsigned Scope = JumpScope;
832 // Walk out the "scope chain" for this scope, looking for a scope
833 // we've marked reachable. For well-formed code this amortizes
834 // to O(JumpScopes.size() / Scopes.size()): we only iterate
835 // when we see something unmarked, and in well-formed code we
836 // mark everything we iterate past.
837 bool IsReachable = false;
838 while (true) {
839 if (Reachable.test(Idx: Scope)) {
840 // If we find something reachable, mark all the scopes we just
841 // walked through as reachable.
842 for (unsigned S = JumpScope; S != Scope; S = Scopes[S].ParentScope)
843 Reachable.set(S);
844 IsReachable = true;
845 break;
846 }
847
848 // Don't walk out if we've reached the top-level scope or we've
849 // gotten shallower than the shallowest reachable scope.
850 if (Scope == 0 || Scope < Min) break;
851
852 // Don't walk out through an out-diagnostic.
853 if (Scopes[Scope].OutDiag) break;
854
855 Scope = Scopes[Scope].ParentScope;
856 }
857
858 // Only diagnose if we didn't find something.
859 if (IsReachable) continue;
860
861 DiagnoseIndirectOrAsmJump(IG: JumpStmt, IGScope: JumpScope, Target: TargetLabel, TargetScope);
862 }
863 }
864}
865
866/// Return true if a particular error+note combination must be downgraded to a
867/// warning in Microsoft mode.
868static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) {
869 return (JumpDiag == diag::err_goto_into_protected_scope &&
870 (InDiagNote == diag::note_protected_by_variable_init ||
871 InDiagNote == diag::note_protected_by_variable_nontriv_destructor));
872}
873
874/// Return true if a particular note should be downgraded to a compatibility
875/// warning in C++11 mode.
876static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) {
877 return S.getLangOpts().CPlusPlus11 &&
878 InDiagNote == diag::note_protected_by_variable_non_pod;
879}
880
881/// Returns true if a particular note should be a C++ compatibility warning in
882/// C mode with -Wc++-compat.
883static bool IsCppCompatWarning(Sema &S, unsigned InDiagNote) {
884 return !S.getLangOpts().CPlusPlus &&
885 InDiagNote == diag::note_protected_by_variable_init;
886}
887
888/// Produce primary diagnostic for an indirect jump statement.
889static void DiagnoseIndirectOrAsmJumpStmt(Sema &S, Stmt *Jump,
890 LabelDecl *Target, bool &Diagnosed) {
891 if (Diagnosed)
892 return;
893 bool IsAsmGoto = isa<GCCAsmStmt>(Val: Jump);
894 S.Diag(Jump->getBeginLoc(), diag::err_indirect_goto_in_protected_scope)
895 << IsAsmGoto;
896 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
897 << IsAsmGoto;
898 Diagnosed = true;
899}
900
901/// Produce note diagnostics for a jump into a protected scope.
902void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {
903 if (CHECK_PERMISSIVE(ToScopes.empty()))
904 return;
905 for (unsigned I = 0, E = ToScopes.size(); I != E; ++I)
906 if (Scopes[ToScopes[I]].InDiag)
907 S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag);
908}
909
910/// Diagnose an indirect jump which is known to cross scopes.
911void JumpScopeChecker::DiagnoseIndirectOrAsmJump(Stmt *Jump, unsigned JumpScope,
912 LabelDecl *Target,
913 unsigned TargetScope) {
914 if (CHECK_PERMISSIVE(JumpScope == TargetScope))
915 return;
916
917 unsigned Common = GetDeepestCommonScope(A: JumpScope, B: TargetScope);
918 bool Diagnosed = false;
919
920 // Walk out the scope chain until we reach the common ancestor.
921 for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope)
922 if (Scopes[I].OutDiag) {
923 DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed);
924 S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);
925 }
926
927 SmallVector<unsigned, 10> ToScopesCXX98Compat, ToScopesCppCompat;
928
929 // Now walk into the scopes containing the label whose address was taken.
930 for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope)
931 if (IsCXX98CompatWarning(S, InDiagNote: Scopes[I].InDiag))
932 ToScopesCXX98Compat.push_back(Elt: I);
933 else if (IsCppCompatWarning(S, InDiagNote: Scopes[I].InDiag))
934 ToScopesCppCompat.push_back(Elt: I);
935 else if (Scopes[I].InDiag) {
936 DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed);
937 S.Diag(Scopes[I].Loc, Scopes[I].InDiag);
938 }
939
940 // Diagnose this jump if it would be ill-formed in C++[98].
941 if (!Diagnosed) {
942 bool IsAsmGoto = isa<GCCAsmStmt>(Val: Jump);
943 auto Diag = [&](unsigned DiagId, const SmallVectorImpl<unsigned> &Notes) {
944 S.Diag(Jump->getBeginLoc(), DiagId) << IsAsmGoto;
945 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target)
946 << IsAsmGoto;
947 NoteJumpIntoScopes(ToScopes: Notes);
948 };
949 if (!ToScopesCXX98Compat.empty())
950 Diag(diag::warn_cxx98_compat_indirect_goto_in_protected_scope,
951 ToScopesCXX98Compat);
952 else if (!ToScopesCppCompat.empty())
953 Diag(diag::warn_cpp_compat_indirect_goto_in_protected_scope,
954 ToScopesCppCompat);
955 }
956}
957
958/// CheckJump - Validate that the specified jump statement is valid: that it is
959/// jumping within or out of its current scope, not into a deeper one.
960void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
961 unsigned JumpDiagError,
962 unsigned JumpDiagWarning,
963 unsigned JumpDiagCompat) {
964 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(From)))
965 return;
966 if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To)))
967 return;
968
969 unsigned FromScope = LabelAndGotoScopes[From];
970 unsigned ToScope = LabelAndGotoScopes[To];
971
972 // Common case: exactly the same scope, which is fine.
973 if (FromScope == ToScope) return;
974
975 // Warn on gotos out of __finally blocks.
976 if (isa<GotoStmt>(Val: From) || isa<IndirectGotoStmt>(Val: From)) {
977 // If FromScope > ToScope, FromScope is more nested and the jump goes to a
978 // less nested scope. Check if it crosses a __finally along the way.
979 for (unsigned I = FromScope; I > ToScope; I = Scopes[I].ParentScope) {
980 if (Scopes[I].InDiag == diag::note_protected_by_seh_finally) {
981 S.Diag(From->getBeginLoc(), diag::warn_jump_out_of_seh_finally);
982 break;
983 } else if (Scopes[I].InDiag ==
984 diag::note_omp_protected_structured_block) {
985 S.Diag(From->getBeginLoc(), diag::err_goto_into_protected_scope);
986 S.Diag(To->getBeginLoc(), diag::note_omp_exits_structured_block);
987 break;
988 } else if (Scopes[I].InDiag ==
989 diag::note_acc_branch_into_compute_construct) {
990 S.Diag(From->getBeginLoc(), diag::err_goto_into_protected_scope);
991 S.Diag(Scopes[I].Loc, diag::note_acc_branch_out_of_compute_construct);
992 return;
993 }
994 }
995 }
996
997 unsigned CommonScope = GetDeepestCommonScope(A: FromScope, B: ToScope);
998
999 // It's okay to jump out from a nested scope.
1000 if (CommonScope == ToScope) return;
1001
1002 // Pull out (and reverse) any scopes we might need to diagnose skipping.
1003 SmallVector<unsigned, 10> ToScopesCompat;
1004 SmallVector<unsigned, 10> ToScopesError;
1005 SmallVector<unsigned, 10> ToScopesWarning;
1006 for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) {
1007 if (S.getLangOpts().MSVCCompat && S.getLangOpts().CPlusPlus &&
1008 JumpDiagWarning != 0 &&
1009 IsMicrosoftJumpWarning(JumpDiag: JumpDiagError, InDiagNote: Scopes[I].InDiag))
1010 ToScopesWarning.push_back(Elt: I);
1011 else if (IsCXX98CompatWarning(S, InDiagNote: Scopes[I].InDiag) ||
1012 IsCppCompatWarning(S, InDiagNote: Scopes[I].InDiag))
1013 ToScopesCompat.push_back(Elt: I);
1014 else if (Scopes[I].InDiag)
1015 ToScopesError.push_back(Elt: I);
1016 }
1017
1018 // Handle warnings.
1019 if (!ToScopesWarning.empty()) {
1020 S.Diag(DiagLoc, JumpDiagWarning);
1021 NoteJumpIntoScopes(ToScopes: ToScopesWarning);
1022 assert(isa<LabelStmt>(To));
1023 LabelStmt *Label = cast<LabelStmt>(Val: To);
1024 Label->setSideEntry(true);
1025 }
1026
1027 // Handle errors.
1028 if (!ToScopesError.empty()) {
1029 S.Diag(DiagLoc, JumpDiagError);
1030 NoteJumpIntoScopes(ToScopes: ToScopesError);
1031 }
1032
1033 // Handle -Wc++98-compat or -Wc++-compat warnings if the jump is well-formed.
1034 if (ToScopesError.empty() && !ToScopesCompat.empty()) {
1035 S.Diag(DiagLoc, JumpDiagCompat);
1036 NoteJumpIntoScopes(ToScopes: ToScopesCompat);
1037 }
1038}
1039
1040void JumpScopeChecker::CheckGotoStmt(GotoStmt *GS) {
1041 if (GS->getLabel()->isMSAsmLabel()) {
1042 S.Diag(GS->getGotoLoc(), diag::err_goto_ms_asm_label)
1043 << GS->getLabel()->getIdentifier();
1044 S.Diag(GS->getLabel()->getLocation(), diag::note_goto_ms_asm_label)
1045 << GS->getLabel()->getIdentifier();
1046 }
1047}
1048
1049void JumpScopeChecker::VerifyMustTailStmts() {
1050 for (AttributedStmt *AS : MustTailStmts) {
1051 for (unsigned I = LabelAndGotoScopes[AS]; I; I = Scopes[I].ParentScope) {
1052 if (Scopes[I].OutDiag) {
1053 S.Diag(AS->getBeginLoc(), diag::err_musttail_scope);
1054 S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);
1055 }
1056 }
1057 }
1058}
1059
1060const Attr *JumpScopeChecker::GetMustTailAttr(AttributedStmt *AS) {
1061 ArrayRef<const Attr *> Attrs = AS->getAttrs();
1062 const auto *Iter =
1063 llvm::find_if(Range&: Attrs, P: [](const Attr *A) { return isa<MustTailAttr>(A); });
1064 return Iter != Attrs.end() ? *Iter : nullptr;
1065}
1066
1067void Sema::DiagnoseInvalidJumps(Stmt *Body) {
1068 (void)JumpScopeChecker(Body, *this);
1069}
1070

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source code of clang/lib/Sema/JumpDiagnostics.cpp