1 //===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- C++ -*-=//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the JumpScopeChecker class, which is used to diagnose
11 // jumps that enter a protected scope in an invalid way.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #include "clang/Sema/SemaInternal.h"
16 #include "clang/AST/DeclCXX.h"
17 #include "clang/AST/Expr.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/StmtCXX.h"
20 #include "clang/AST/StmtObjC.h"
21 #include "llvm/ADT/BitVector.h"
22 using namespace clang;
23
24 namespace {
25
26 /// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps
27 /// into VLA and other protected scopes. For example, this rejects:
28 /// goto L;
29 /// int a[n];
30 /// L:
31 ///
32 class JumpScopeChecker {
33 Sema &S;
34
35 /// GotoScope - This is a record that we use to keep track of all of the
36 /// scopes that are introduced by VLAs and other things that scope jumps like
37 /// gotos. This scope tree has nothing to do with the source scope tree,
38 /// because you can have multiple VLA scopes per compound statement, and most
39 /// compound statements don't introduce any scopes.
40 struct GotoScope {
41 /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for
42 /// the parent scope is the function body.
43 unsigned ParentScope;
44
45 /// InDiag - The note to emit if there is a jump into this scope.
46 unsigned InDiag;
47
48 /// OutDiag - The note to emit if there is an indirect jump out
49 /// of this scope. Direct jumps always clean up their current scope
50 /// in an orderly way.
51 unsigned OutDiag;
52
53 /// Loc - Location to emit the diagnostic.
54 SourceLocation Loc;
55
GotoScope__anon083d9f2b0111::JumpScopeChecker::GotoScope56 GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag,
57 SourceLocation L)
58 : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {}
59 };
60
61 SmallVector<GotoScope, 48> Scopes;
62 llvm::DenseMap<Stmt*, unsigned> LabelAndGotoScopes;
63 SmallVector<Stmt*, 16> Jumps;
64
65 SmallVector<IndirectGotoStmt*, 4> IndirectJumps;
66 SmallVector<LabelDecl*, 4> IndirectJumpTargets;
67 public:
68 JumpScopeChecker(Stmt *Body, Sema &S);
69 private:
70 void BuildScopeInformation(Decl *D, unsigned &ParentScope);
71 void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl,
72 unsigned &ParentScope);
73 void BuildScopeInformation(Stmt *S, unsigned &origParentScope);
74
75 void VerifyJumps();
76 void VerifyIndirectJumps();
77 void NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes);
78 void DiagnoseIndirectJump(IndirectGotoStmt *IG, unsigned IGScope,
79 LabelDecl *Target, unsigned TargetScope);
80 void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
81 unsigned JumpDiag, unsigned JumpDiagWarning,
82 unsigned JumpDiagCXX98Compat);
83
84 unsigned GetDeepestCommonScope(unsigned A, unsigned B);
85 };
86 } // end anonymous namespace
87
88
JumpScopeChecker(Stmt * Body,Sema & s)89 JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s) {
90 // Add a scope entry for function scope.
91 Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation()));
92
93 // Build information for the top level compound statement, so that we have a
94 // defined scope record for every "goto" and label.
95 unsigned BodyParentScope = 0;
96 BuildScopeInformation(Body, BodyParentScope);
97
98 // Check that all jumps we saw are kosher.
99 VerifyJumps();
100 VerifyIndirectJumps();
101 }
102
103 /// GetDeepestCommonScope - Finds the innermost scope enclosing the
104 /// two scopes.
GetDeepestCommonScope(unsigned A,unsigned B)105 unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) {
106 while (A != B) {
107 // Inner scopes are created after outer scopes and therefore have
108 // higher indices.
109 if (A < B) {
110 assert(Scopes[B].ParentScope < B);
111 B = Scopes[B].ParentScope;
112 } else {
113 assert(Scopes[A].ParentScope < A);
114 A = Scopes[A].ParentScope;
115 }
116 }
117 return A;
118 }
119
120 typedef std::pair<unsigned,unsigned> ScopePair;
121
122 /// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a
123 /// diagnostic that should be emitted if control goes over it. If not, return 0.
GetDiagForGotoScopeDecl(ASTContext & Context,const Decl * D)124 static ScopePair GetDiagForGotoScopeDecl(ASTContext &Context, const Decl *D) {
125 if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
126 unsigned InDiag = 0;
127 if (VD->getType()->isVariablyModifiedType())
128 InDiag = diag::note_protected_by_vla;
129
130 if (VD->hasAttr<BlocksAttr>())
131 return ScopePair(diag::note_protected_by___block,
132 diag::note_exits___block);
133
134 if (VD->hasAttr<CleanupAttr>())
135 return ScopePair(diag::note_protected_by_cleanup,
136 diag::note_exits_cleanup);
137
138 if (Context.getLangOpts().ObjCAutoRefCount && VD->hasLocalStorage()) {
139 switch (VD->getType().getObjCLifetime()) {
140 case Qualifiers::OCL_None:
141 case Qualifiers::OCL_ExplicitNone:
142 case Qualifiers::OCL_Autoreleasing:
143 break;
144
145 case Qualifiers::OCL_Strong:
146 case Qualifiers::OCL_Weak:
147 return ScopePair(diag::note_protected_by_objc_ownership,
148 diag::note_exits_objc_ownership);
149 }
150 }
151
152 if (Context.getLangOpts().CPlusPlus && VD->hasLocalStorage()) {
153 // C++11 [stmt.dcl]p3:
154 // A program that jumps from a point where a variable with automatic
155 // storage duration is not in scope to a point where it is in scope
156 // is ill-formed unless the variable has scalar type, class type with
157 // a trivial default constructor and a trivial destructor, a
158 // cv-qualified version of one of these types, or an array of one of
159 // the preceding types and is declared without an initializer.
160
161 // C++03 [stmt.dcl.p3:
162 // A program that jumps from a point where a local variable
163 // with automatic storage duration is not in scope to a point
164 // where it is in scope is ill-formed unless the variable has
165 // POD type and is declared without an initializer.
166
167 const Expr *Init = VD->getInit();
168 if (!Init)
169 return ScopePair(InDiag, 0);
170
171 const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Init);
172 if (EWC)
173 Init = EWC->getSubExpr();
174
175 const MaterializeTemporaryExpr *M = NULL;
176 Init = Init->findMaterializedTemporary(M);
177
178 SmallVector<SubobjectAdjustment, 2> Adjustments;
179 Init = Init->skipRValueSubobjectAdjustments(Adjustments);
180
181 QualType QT = Init->getType();
182 if (QT.isNull())
183 return ScopePair(diag::note_protected_by_variable_init, 0);
184
185 const Type *T = QT.getTypePtr();
186 if (T->isArrayType())
187 T = T->getBaseElementTypeUnsafe();
188
189 const CXXRecordDecl *Record = T->getAsCXXRecordDecl();
190 if (!Record)
191 return ScopePair(diag::note_protected_by_variable_init, 0);
192
193 // If we need to call a non trivial destructor for this variable,
194 // record an out diagnostic.
195 unsigned OutDiag = 0;
196 if (!Init->isGLValue() && !Record->hasTrivialDestructor())
197 OutDiag = diag::note_exits_dtor;
198
199 if (const CXXConstructExpr *cce = dyn_cast<CXXConstructExpr>(Init)) {
200 const CXXConstructorDecl *ctor = cce->getConstructor();
201 if (ctor->isTrivial() && ctor->isDefaultConstructor()) {
202 if (OutDiag)
203 InDiag = diag::note_protected_by_variable_nontriv_destructor;
204 else if (!Record->isPOD())
205 InDiag = diag::note_protected_by_variable_non_pod;
206 return ScopePair(InDiag, OutDiag);
207 }
208 }
209
210 return ScopePair(diag::note_protected_by_variable_init, OutDiag);
211 }
212
213 return ScopePair(InDiag, 0);
214 }
215
216 if (const TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
217 if (TD->getUnderlyingType()->isVariablyModifiedType())
218 return ScopePair(diag::note_protected_by_vla_typedef, 0);
219 }
220
221 if (const TypeAliasDecl *TD = dyn_cast<TypeAliasDecl>(D)) {
222 if (TD->getUnderlyingType()->isVariablyModifiedType())
223 return ScopePair(diag::note_protected_by_vla_type_alias, 0);
224 }
225
226 return ScopePair(0U, 0U);
227 }
228
229 /// \brief Build scope information for a declaration that is part of a DeclStmt.
BuildScopeInformation(Decl * D,unsigned & ParentScope)230 void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) {
231 // If this decl causes a new scope, push and switch to it.
232 std::pair<unsigned,unsigned> Diags = GetDiagForGotoScopeDecl(S.Context, D);
233 if (Diags.first || Diags.second) {
234 Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second,
235 D->getLocation()));
236 ParentScope = Scopes.size()-1;
237 }
238
239 // If the decl has an initializer, walk it with the potentially new
240 // scope we just installed.
241 if (VarDecl *VD = dyn_cast<VarDecl>(D))
242 if (Expr *Init = VD->getInit())
243 BuildScopeInformation(Init, ParentScope);
244 }
245
246 /// \brief Build scope information for a captured block literal variables.
BuildScopeInformation(VarDecl * D,const BlockDecl * BDecl,unsigned & ParentScope)247 void JumpScopeChecker::BuildScopeInformation(VarDecl *D,
248 const BlockDecl *BDecl,
249 unsigned &ParentScope) {
250 // exclude captured __block variables; there's no destructor
251 // associated with the block literal for them.
252 if (D->hasAttr<BlocksAttr>())
253 return;
254 QualType T = D->getType();
255 QualType::DestructionKind destructKind = T.isDestructedType();
256 if (destructKind != QualType::DK_none) {
257 std::pair<unsigned,unsigned> Diags;
258 switch (destructKind) {
259 case QualType::DK_cxx_destructor:
260 Diags = ScopePair(diag::note_enters_block_captures_cxx_obj,
261 diag::note_exits_block_captures_cxx_obj);
262 break;
263 case QualType::DK_objc_strong_lifetime:
264 Diags = ScopePair(diag::note_enters_block_captures_strong,
265 diag::note_exits_block_captures_strong);
266 break;
267 case QualType::DK_objc_weak_lifetime:
268 Diags = ScopePair(diag::note_enters_block_captures_weak,
269 diag::note_exits_block_captures_weak);
270 break;
271 case QualType::DK_none:
272 llvm_unreachable("non-lifetime captured variable");
273 }
274 SourceLocation Loc = D->getLocation();
275 if (Loc.isInvalid())
276 Loc = BDecl->getLocation();
277 Scopes.push_back(GotoScope(ParentScope,
278 Diags.first, Diags.second, Loc));
279 ParentScope = Scopes.size()-1;
280 }
281 }
282
283 /// BuildScopeInformation - The statements from CI to CE are known to form a
284 /// coherent VLA scope with a specified parent node. Walk through the
285 /// statements, adding any labels or gotos to LabelAndGotoScopes and recursively
286 /// walking the AST as needed.
BuildScopeInformation(Stmt * S,unsigned & origParentScope)287 void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned &origParentScope) {
288 // If this is a statement, rather than an expression, scopes within it don't
289 // propagate out into the enclosing scope. Otherwise we have to worry
290 // about block literals, which have the lifetime of their enclosing statement.
291 unsigned independentParentScope = origParentScope;
292 unsigned &ParentScope = ((isa<Expr>(S) && !isa<StmtExpr>(S))
293 ? origParentScope : independentParentScope);
294
295 bool SkipFirstSubStmt = false;
296
297 // If we found a label, remember that it is in ParentScope scope.
298 switch (S->getStmtClass()) {
299 case Stmt::AddrLabelExprClass:
300 IndirectJumpTargets.push_back(cast<AddrLabelExpr>(S)->getLabel());
301 break;
302
303 case Stmt::IndirectGotoStmtClass:
304 // "goto *&&lbl;" is a special case which we treat as equivalent
305 // to a normal goto. In addition, we don't calculate scope in the
306 // operand (to avoid recording the address-of-label use), which
307 // works only because of the restricted set of expressions which
308 // we detect as constant targets.
309 if (cast<IndirectGotoStmt>(S)->getConstantTarget()) {
310 LabelAndGotoScopes[S] = ParentScope;
311 Jumps.push_back(S);
312 return;
313 }
314
315 LabelAndGotoScopes[S] = ParentScope;
316 IndirectJumps.push_back(cast<IndirectGotoStmt>(S));
317 break;
318
319 case Stmt::SwitchStmtClass:
320 // Evaluate the condition variable before entering the scope of the switch
321 // statement.
322 if (VarDecl *Var = cast<SwitchStmt>(S)->getConditionVariable()) {
323 BuildScopeInformation(Var, ParentScope);
324 SkipFirstSubStmt = true;
325 }
326 // Fall through
327
328 case Stmt::GotoStmtClass:
329 // Remember both what scope a goto is in as well as the fact that we have
330 // it. This makes the second scan not have to walk the AST again.
331 LabelAndGotoScopes[S] = ParentScope;
332 Jumps.push_back(S);
333 break;
334
335 case Stmt::CXXTryStmtClass: {
336 CXXTryStmt *TS = cast<CXXTryStmt>(S);
337 unsigned newParentScope;
338 Scopes.push_back(GotoScope(ParentScope,
339 diag::note_protected_by_cxx_try,
340 diag::note_exits_cxx_try,
341 TS->getSourceRange().getBegin()));
342 if (Stmt *TryBlock = TS->getTryBlock())
343 BuildScopeInformation(TryBlock, (newParentScope = Scopes.size()-1));
344
345 // Jump from the catch into the try is not allowed either.
346 for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) {
347 CXXCatchStmt *CS = TS->getHandler(I);
348 Scopes.push_back(GotoScope(ParentScope,
349 diag::note_protected_by_cxx_catch,
350 diag::note_exits_cxx_catch,
351 CS->getSourceRange().getBegin()));
352 BuildScopeInformation(CS->getHandlerBlock(),
353 (newParentScope = Scopes.size()-1));
354 }
355 return;
356 }
357
358 default:
359 break;
360 }
361
362 for (Stmt::child_range CI = S->children(); CI; ++CI) {
363 if (SkipFirstSubStmt) {
364 SkipFirstSubStmt = false;
365 continue;
366 }
367
368 Stmt *SubStmt = *CI;
369 if (SubStmt == 0) continue;
370
371 // Cases, labels, and defaults aren't "scope parents". It's also
372 // important to handle these iteratively instead of recursively in
373 // order to avoid blowing out the stack.
374 while (true) {
375 Stmt *Next;
376 if (CaseStmt *CS = dyn_cast<CaseStmt>(SubStmt))
377 Next = CS->getSubStmt();
378 else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SubStmt))
379 Next = DS->getSubStmt();
380 else if (LabelStmt *LS = dyn_cast<LabelStmt>(SubStmt))
381 Next = LS->getSubStmt();
382 else
383 break;
384
385 LabelAndGotoScopes[SubStmt] = ParentScope;
386 SubStmt = Next;
387 }
388
389 // If this is a declstmt with a VLA definition, it defines a scope from here
390 // to the end of the containing context.
391 if (DeclStmt *DS = dyn_cast<DeclStmt>(SubStmt)) {
392 // The decl statement creates a scope if any of the decls in it are VLAs
393 // or have the cleanup attribute.
394 for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end();
395 I != E; ++I)
396 BuildScopeInformation(*I, ParentScope);
397 continue;
398 }
399 // Disallow jumps into any part of an @try statement by pushing a scope and
400 // walking all sub-stmts in that scope.
401 if (ObjCAtTryStmt *AT = dyn_cast<ObjCAtTryStmt>(SubStmt)) {
402 unsigned newParentScope;
403 // Recursively walk the AST for the @try part.
404 Scopes.push_back(GotoScope(ParentScope,
405 diag::note_protected_by_objc_try,
406 diag::note_exits_objc_try,
407 AT->getAtTryLoc()));
408 if (Stmt *TryPart = AT->getTryBody())
409 BuildScopeInformation(TryPart, (newParentScope = Scopes.size()-1));
410
411 // Jump from the catch to the finally or try is not valid.
412 for (unsigned I = 0, N = AT->getNumCatchStmts(); I != N; ++I) {
413 ObjCAtCatchStmt *AC = AT->getCatchStmt(I);
414 Scopes.push_back(GotoScope(ParentScope,
415 diag::note_protected_by_objc_catch,
416 diag::note_exits_objc_catch,
417 AC->getAtCatchLoc()));
418 // @catches are nested and it isn't
419 BuildScopeInformation(AC->getCatchBody(),
420 (newParentScope = Scopes.size()-1));
421 }
422
423 // Jump from the finally to the try or catch is not valid.
424 if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) {
425 Scopes.push_back(GotoScope(ParentScope,
426 diag::note_protected_by_objc_finally,
427 diag::note_exits_objc_finally,
428 AF->getAtFinallyLoc()));
429 BuildScopeInformation(AF, (newParentScope = Scopes.size()-1));
430 }
431
432 continue;
433 }
434
435 unsigned newParentScope;
436 // Disallow jumps into the protected statement of an @synchronized, but
437 // allow jumps into the object expression it protects.
438 if (ObjCAtSynchronizedStmt *AS = dyn_cast<ObjCAtSynchronizedStmt>(SubStmt)){
439 // Recursively walk the AST for the @synchronized object expr, it is
440 // evaluated in the normal scope.
441 BuildScopeInformation(AS->getSynchExpr(), ParentScope);
442
443 // Recursively walk the AST for the @synchronized part, protected by a new
444 // scope.
445 Scopes.push_back(GotoScope(ParentScope,
446 diag::note_protected_by_objc_synchronized,
447 diag::note_exits_objc_synchronized,
448 AS->getAtSynchronizedLoc()));
449 BuildScopeInformation(AS->getSynchBody(),
450 (newParentScope = Scopes.size()-1));
451 continue;
452 }
453
454 // Disallow jumps into the protected statement of an @autoreleasepool.
455 if (ObjCAutoreleasePoolStmt *AS = dyn_cast<ObjCAutoreleasePoolStmt>(SubStmt)){
456 // Recursively walk the AST for the @autoreleasepool part, protected by a new
457 // scope.
458 Scopes.push_back(GotoScope(ParentScope,
459 diag::note_protected_by_objc_autoreleasepool,
460 diag::note_exits_objc_autoreleasepool,
461 AS->getAtLoc()));
462 BuildScopeInformation(AS->getSubStmt(), (newParentScope = Scopes.size()-1));
463 continue;
464 }
465
466 // Disallow jumps past full-expressions that use blocks with
467 // non-trivial cleanups of their captures. This is theoretically
468 // implementable but a lot of work which we haven't felt up to doing.
469 if (ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(SubStmt)) {
470 for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) {
471 const BlockDecl *BDecl = EWC->getObject(i);
472 for (BlockDecl::capture_const_iterator ci = BDecl->capture_begin(),
473 ce = BDecl->capture_end(); ci != ce; ++ci) {
474 VarDecl *variable = ci->getVariable();
475 BuildScopeInformation(variable, BDecl, ParentScope);
476 }
477 }
478 }
479
480 // Recursively walk the AST.
481 BuildScopeInformation(SubStmt, ParentScope);
482 }
483 }
484
485 /// VerifyJumps - Verify each element of the Jumps array to see if they are
486 /// valid, emitting diagnostics if not.
VerifyJumps()487 void JumpScopeChecker::VerifyJumps() {
488 while (!Jumps.empty()) {
489 Stmt *Jump = Jumps.pop_back_val();
490
491 // With a goto,
492 if (GotoStmt *GS = dyn_cast<GotoStmt>(Jump)) {
493 CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(),
494 diag::err_goto_into_protected_scope,
495 diag::warn_goto_into_protected_scope,
496 diag::warn_cxx98_compat_goto_into_protected_scope);
497 continue;
498 }
499
500 // We only get indirect gotos here when they have a constant target.
501 if (IndirectGotoStmt *IGS = dyn_cast<IndirectGotoStmt>(Jump)) {
502 LabelDecl *Target = IGS->getConstantTarget();
503 CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(),
504 diag::err_goto_into_protected_scope,
505 diag::warn_goto_into_protected_scope,
506 diag::warn_cxx98_compat_goto_into_protected_scope);
507 continue;
508 }
509
510 SwitchStmt *SS = cast<SwitchStmt>(Jump);
511 for (SwitchCase *SC = SS->getSwitchCaseList(); SC;
512 SC = SC->getNextSwitchCase()) {
513 assert(LabelAndGotoScopes.count(SC) && "Case not visited?");
514 SourceLocation Loc;
515 if (CaseStmt *CS = dyn_cast<CaseStmt>(SC))
516 Loc = CS->getLocStart();
517 else if (DefaultStmt *DS = dyn_cast<DefaultStmt>(SC))
518 Loc = DS->getLocStart();
519 else
520 Loc = SC->getLocStart();
521 CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0,
522 diag::warn_cxx98_compat_switch_into_protected_scope);
523 }
524 }
525 }
526
527 /// VerifyIndirectJumps - Verify whether any possible indirect jump
528 /// might cross a protection boundary. Unlike direct jumps, indirect
529 /// jumps count cleanups as protection boundaries: since there's no
530 /// way to know where the jump is going, we can't implicitly run the
531 /// right cleanups the way we can with direct jumps.
532 ///
533 /// Thus, an indirect jump is "trivial" if it bypasses no
534 /// initializations and no teardowns. More formally, an indirect jump
535 /// from A to B is trivial if the path out from A to DCA(A,B) is
536 /// trivial and the path in from DCA(A,B) to B is trivial, where
537 /// DCA(A,B) is the deepest common ancestor of A and B.
538 /// Jump-triviality is transitive but asymmetric.
539 ///
540 /// A path in is trivial if none of the entered scopes have an InDiag.
541 /// A path out is trivial is none of the exited scopes have an OutDiag.
542 ///
543 /// Under these definitions, this function checks that the indirect
544 /// jump between A and B is trivial for every indirect goto statement A
545 /// and every label B whose address was taken in the function.
VerifyIndirectJumps()546 void JumpScopeChecker::VerifyIndirectJumps() {
547 if (IndirectJumps.empty()) return;
548
549 // If there aren't any address-of-label expressions in this function,
550 // complain about the first indirect goto.
551 if (IndirectJumpTargets.empty()) {
552 S.Diag(IndirectJumps[0]->getGotoLoc(),
553 diag::err_indirect_goto_without_addrlabel);
554 return;
555 }
556
557 // Collect a single representative of every scope containing an
558 // indirect goto. For most code bases, this substantially cuts
559 // down on the number of jump sites we'll have to consider later.
560 typedef std::pair<unsigned, IndirectGotoStmt*> JumpScope;
561 SmallVector<JumpScope, 32> JumpScopes;
562 {
563 llvm::DenseMap<unsigned, IndirectGotoStmt*> JumpScopesMap;
564 for (SmallVectorImpl<IndirectGotoStmt*>::iterator
565 I = IndirectJumps.begin(), E = IndirectJumps.end(); I != E; ++I) {
566 IndirectGotoStmt *IG = *I;
567 assert(LabelAndGotoScopes.count(IG) &&
568 "indirect jump didn't get added to scopes?");
569 unsigned IGScope = LabelAndGotoScopes[IG];
570 IndirectGotoStmt *&Entry = JumpScopesMap[IGScope];
571 if (!Entry) Entry = IG;
572 }
573 JumpScopes.reserve(JumpScopesMap.size());
574 for (llvm::DenseMap<unsigned, IndirectGotoStmt*>::iterator
575 I = JumpScopesMap.begin(), E = JumpScopesMap.end(); I != E; ++I)
576 JumpScopes.push_back(*I);
577 }
578
579 // Collect a single representative of every scope containing a
580 // label whose address was taken somewhere in the function.
581 // For most code bases, there will be only one such scope.
582 llvm::DenseMap<unsigned, LabelDecl*> TargetScopes;
583 for (SmallVectorImpl<LabelDecl*>::iterator
584 I = IndirectJumpTargets.begin(), E = IndirectJumpTargets.end();
585 I != E; ++I) {
586 LabelDecl *TheLabel = *I;
587 assert(LabelAndGotoScopes.count(TheLabel->getStmt()) &&
588 "Referenced label didn't get added to scopes?");
589 unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()];
590 LabelDecl *&Target = TargetScopes[LabelScope];
591 if (!Target) Target = TheLabel;
592 }
593
594 // For each target scope, make sure it's trivially reachable from
595 // every scope containing a jump site.
596 //
597 // A path between scopes always consists of exitting zero or more
598 // scopes, then entering zero or more scopes. We build a set of
599 // of scopes S from which the target scope can be trivially
600 // entered, then verify that every jump scope can be trivially
601 // exitted to reach a scope in S.
602 llvm::BitVector Reachable(Scopes.size(), false);
603 for (llvm::DenseMap<unsigned,LabelDecl*>::iterator
604 TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) {
605 unsigned TargetScope = TI->first;
606 LabelDecl *TargetLabel = TI->second;
607
608 Reachable.reset();
609
610 // Mark all the enclosing scopes from which you can safely jump
611 // into the target scope. 'Min' will end up being the index of
612 // the shallowest such scope.
613 unsigned Min = TargetScope;
614 while (true) {
615 Reachable.set(Min);
616
617 // Don't go beyond the outermost scope.
618 if (Min == 0) break;
619
620 // Stop if we can't trivially enter the current scope.
621 if (Scopes[Min].InDiag) break;
622
623 Min = Scopes[Min].ParentScope;
624 }
625
626 // Walk through all the jump sites, checking that they can trivially
627 // reach this label scope.
628 for (SmallVectorImpl<JumpScope>::iterator
629 I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) {
630 unsigned Scope = I->first;
631
632 // Walk out the "scope chain" for this scope, looking for a scope
633 // we've marked reachable. For well-formed code this amortizes
634 // to O(JumpScopes.size() / Scopes.size()): we only iterate
635 // when we see something unmarked, and in well-formed code we
636 // mark everything we iterate past.
637 bool IsReachable = false;
638 while (true) {
639 if (Reachable.test(Scope)) {
640 // If we find something reachable, mark all the scopes we just
641 // walked through as reachable.
642 for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope)
643 Reachable.set(S);
644 IsReachable = true;
645 break;
646 }
647
648 // Don't walk out if we've reached the top-level scope or we've
649 // gotten shallower than the shallowest reachable scope.
650 if (Scope == 0 || Scope < Min) break;
651
652 // Don't walk out through an out-diagnostic.
653 if (Scopes[Scope].OutDiag) break;
654
655 Scope = Scopes[Scope].ParentScope;
656 }
657
658 // Only diagnose if we didn't find something.
659 if (IsReachable) continue;
660
661 DiagnoseIndirectJump(I->second, I->first, TargetLabel, TargetScope);
662 }
663 }
664 }
665
666 /// Return true if a particular error+note combination must be downgraded to a
667 /// warning in Microsoft mode.
IsMicrosoftJumpWarning(unsigned JumpDiag,unsigned InDiagNote)668 static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) {
669 return (JumpDiag == diag::err_goto_into_protected_scope &&
670 (InDiagNote == diag::note_protected_by_variable_init ||
671 InDiagNote == diag::note_protected_by_variable_nontriv_destructor));
672 }
673
674 /// Return true if a particular note should be downgraded to a compatibility
675 /// warning in C++11 mode.
IsCXX98CompatWarning(Sema & S,unsigned InDiagNote)676 static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) {
677 return S.getLangOpts().CPlusPlus11 &&
678 InDiagNote == diag::note_protected_by_variable_non_pod;
679 }
680
681 /// Produce primary diagnostic for an indirect jump statement.
DiagnoseIndirectJumpStmt(Sema & S,IndirectGotoStmt * Jump,LabelDecl * Target,bool & Diagnosed)682 static void DiagnoseIndirectJumpStmt(Sema &S, IndirectGotoStmt *Jump,
683 LabelDecl *Target, bool &Diagnosed) {
684 if (Diagnosed)
685 return;
686 S.Diag(Jump->getGotoLoc(), diag::err_indirect_goto_in_protected_scope);
687 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);
688 Diagnosed = true;
689 }
690
691 /// Produce note diagnostics for a jump into a protected scope.
NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes)692 void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef<unsigned> ToScopes) {
693 assert(!ToScopes.empty());
694 for (unsigned I = 0, E = ToScopes.size(); I != E; ++I)
695 if (Scopes[ToScopes[I]].InDiag)
696 S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag);
697 }
698
699 /// Diagnose an indirect jump which is known to cross scopes.
DiagnoseIndirectJump(IndirectGotoStmt * Jump,unsigned JumpScope,LabelDecl * Target,unsigned TargetScope)700 void JumpScopeChecker::DiagnoseIndirectJump(IndirectGotoStmt *Jump,
701 unsigned JumpScope,
702 LabelDecl *Target,
703 unsigned TargetScope) {
704 assert(JumpScope != TargetScope);
705
706 unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope);
707 bool Diagnosed = false;
708
709 // Walk out the scope chain until we reach the common ancestor.
710 for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope)
711 if (Scopes[I].OutDiag) {
712 DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);
713 S.Diag(Scopes[I].Loc, Scopes[I].OutDiag);
714 }
715
716 SmallVector<unsigned, 10> ToScopesCXX98Compat;
717
718 // Now walk into the scopes containing the label whose address was taken.
719 for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope)
720 if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
721 ToScopesCXX98Compat.push_back(I);
722 else if (Scopes[I].InDiag) {
723 DiagnoseIndirectJumpStmt(S, Jump, Target, Diagnosed);
724 S.Diag(Scopes[I].Loc, Scopes[I].InDiag);
725 }
726
727 // Diagnose this jump if it would be ill-formed in C++98.
728 if (!Diagnosed && !ToScopesCXX98Compat.empty()) {
729 S.Diag(Jump->getGotoLoc(),
730 diag::warn_cxx98_compat_indirect_goto_in_protected_scope);
731 S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target);
732 NoteJumpIntoScopes(ToScopesCXX98Compat);
733 }
734 }
735
736 /// CheckJump - Validate that the specified jump statement is valid: that it is
737 /// 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)738 void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc,
739 unsigned JumpDiagError, unsigned JumpDiagWarning,
740 unsigned JumpDiagCXX98Compat) {
741 assert(LabelAndGotoScopes.count(From) && "Jump didn't get added to scopes?");
742 unsigned FromScope = LabelAndGotoScopes[From];
743
744 assert(LabelAndGotoScopes.count(To) && "Jump didn't get added to scopes?");
745 unsigned ToScope = LabelAndGotoScopes[To];
746
747 // Common case: exactly the same scope, which is fine.
748 if (FromScope == ToScope) return;
749
750 unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope);
751
752 // It's okay to jump out from a nested scope.
753 if (CommonScope == ToScope) return;
754
755 // Pull out (and reverse) any scopes we might need to diagnose skipping.
756 SmallVector<unsigned, 10> ToScopesCXX98Compat;
757 SmallVector<unsigned, 10> ToScopesError;
758 SmallVector<unsigned, 10> ToScopesWarning;
759 for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) {
760 if (S.getLangOpts().MicrosoftMode && JumpDiagWarning != 0 &&
761 IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag))
762 ToScopesWarning.push_back(I);
763 else if (IsCXX98CompatWarning(S, Scopes[I].InDiag))
764 ToScopesCXX98Compat.push_back(I);
765 else if (Scopes[I].InDiag)
766 ToScopesError.push_back(I);
767 }
768
769 // Handle warnings.
770 if (!ToScopesWarning.empty()) {
771 S.Diag(DiagLoc, JumpDiagWarning);
772 NoteJumpIntoScopes(ToScopesWarning);
773 }
774
775 // Handle errors.
776 if (!ToScopesError.empty()) {
777 S.Diag(DiagLoc, JumpDiagError);
778 NoteJumpIntoScopes(ToScopesError);
779 }
780
781 // Handle -Wc++98-compat warnings if the jump is well-formed.
782 if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) {
783 S.Diag(DiagLoc, JumpDiagCXX98Compat);
784 NoteJumpIntoScopes(ToScopesCXX98Compat);
785 }
786 }
787
DiagnoseInvalidJumps(Stmt * Body)788 void Sema::DiagnoseInvalidJumps(Stmt *Body) {
789 (void)JumpScopeChecker(Body, *this);
790 }
791