//===--- JumpDiagnostics.cpp - Protected scope jump analysis ------*- C++ -*-=// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This file implements the JumpScopeChecker class, which is used to diagnose // jumps that enter a protected scope in an invalid way. // //===----------------------------------------------------------------------===// #include "clang/AST/DeclCXX.h" #include "clang/AST/Expr.h" #include "clang/AST/ExprCXX.h" #include "clang/AST/StmtCXX.h" #include "clang/AST/StmtObjC.h" #include "clang/AST/StmtOpenMP.h" #include "clang/Basic/SourceLocation.h" #include "clang/Sema/SemaInternal.h" #include "llvm/ADT/BitVector.h" using namespace clang; namespace { /// JumpScopeChecker - This object is used by Sema to diagnose invalid jumps /// into VLA and other protected scopes. For example, this rejects: /// goto L; /// int a[n]; /// L: /// /// We also detect jumps out of protected scopes when it's not possible to do /// cleanups properly. Indirect jumps and ASM jumps can't do cleanups because /// the target is unknown. Return statements with \c [[clang::musttail]] cannot /// handle any cleanups due to the nature of a tail call. class JumpScopeChecker { Sema &S; /// Permissive - True when recovering from errors, in which case precautions /// are taken to handle incomplete scope information. const bool Permissive; /// GotoScope - This is a record that we use to keep track of all of the /// scopes that are introduced by VLAs and other things that scope jumps like /// gotos. This scope tree has nothing to do with the source scope tree, /// because you can have multiple VLA scopes per compound statement, and most /// compound statements don't introduce any scopes. struct GotoScope { /// ParentScope - The index in ScopeMap of the parent scope. This is 0 for /// the parent scope is the function body. unsigned ParentScope; /// InDiag - The note to emit if there is a jump into this scope. unsigned InDiag; /// OutDiag - The note to emit if there is an indirect jump out /// of this scope. Direct jumps always clean up their current scope /// in an orderly way. unsigned OutDiag; /// Loc - Location to emit the diagnostic. SourceLocation Loc; GotoScope(unsigned parentScope, unsigned InDiag, unsigned OutDiag, SourceLocation L) : ParentScope(parentScope), InDiag(InDiag), OutDiag(OutDiag), Loc(L) {} }; SmallVector Scopes; llvm::DenseMap LabelAndGotoScopes; SmallVector Jumps; SmallVector IndirectJumps; SmallVector AsmJumps; SmallVector MustTailStmts; SmallVector IndirectJumpTargets; SmallVector AsmJumpTargets; public: JumpScopeChecker(Stmt *Body, Sema &S); private: void BuildScopeInformation(Decl *D, unsigned &ParentScope); void BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl, unsigned &ParentScope); void BuildScopeInformation(CompoundLiteralExpr *CLE, unsigned &ParentScope); void BuildScopeInformation(Stmt *S, unsigned &origParentScope); void VerifyJumps(); void VerifyIndirectOrAsmJumps(bool IsAsmGoto); void VerifyMustTailStmts(); void NoteJumpIntoScopes(ArrayRef ToScopes); void DiagnoseIndirectOrAsmJump(Stmt *IG, unsigned IGScope, LabelDecl *Target, unsigned TargetScope); void CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc, unsigned JumpDiag, unsigned JumpDiagWarning, unsigned JumpDiagCXX98Compat); void CheckGotoStmt(GotoStmt *GS); const Attr *GetMustTailAttr(AttributedStmt *AS); unsigned GetDeepestCommonScope(unsigned A, unsigned B); }; } // end anonymous namespace #define CHECK_PERMISSIVE(x) (assert(Permissive || !(x)), (Permissive && (x))) JumpScopeChecker::JumpScopeChecker(Stmt *Body, Sema &s) : S(s), Permissive(s.hasAnyUnrecoverableErrorsInThisFunction()) { // Add a scope entry for function scope. Scopes.push_back(GotoScope(~0U, ~0U, ~0U, SourceLocation())); // Build information for the top level compound statement, so that we have a // defined scope record for every "goto" and label. unsigned BodyParentScope = 0; BuildScopeInformation(Body, BodyParentScope); // Check that all jumps we saw are kosher. VerifyJumps(); VerifyIndirectOrAsmJumps(false); VerifyIndirectOrAsmJumps(true); VerifyMustTailStmts(); } /// GetDeepestCommonScope - Finds the innermost scope enclosing the /// two scopes. unsigned JumpScopeChecker::GetDeepestCommonScope(unsigned A, unsigned B) { while (A != B) { // Inner scopes are created after outer scopes and therefore have // higher indices. if (A < B) { assert(Scopes[B].ParentScope < B); B = Scopes[B].ParentScope; } else { assert(Scopes[A].ParentScope < A); A = Scopes[A].ParentScope; } } return A; } typedef std::pair ScopePair; /// GetDiagForGotoScopeDecl - If this decl induces a new goto scope, return a /// diagnostic that should be emitted if control goes over it. If not, return 0. static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D) { if (const VarDecl *VD = dyn_cast(D)) { unsigned InDiag = 0; unsigned OutDiag = 0; if (VD->getType()->isVariablyModifiedType()) InDiag = diag::note_protected_by_vla; if (VD->hasAttr()) return ScopePair(diag::note_protected_by___block, diag::note_exits___block); if (VD->hasAttr()) return ScopePair(diag::note_protected_by_cleanup, diag::note_exits_cleanup); if (VD->hasLocalStorage()) { switch (VD->getType().isDestructedType()) { case QualType::DK_objc_strong_lifetime: return ScopePair(diag::note_protected_by_objc_strong_init, diag::note_exits_objc_strong); case QualType::DK_objc_weak_lifetime: return ScopePair(diag::note_protected_by_objc_weak_init, diag::note_exits_objc_weak); case QualType::DK_nontrivial_c_struct: return ScopePair(diag::note_protected_by_non_trivial_c_struct_init, diag::note_exits_dtor); case QualType::DK_cxx_destructor: OutDiag = diag::note_exits_dtor; break; case QualType::DK_none: break; } } const Expr *Init = VD->getInit(); if (S.Context.getLangOpts().CPlusPlus && VD->hasLocalStorage() && Init) { // C++11 [stmt.dcl]p3: // A program that jumps from a point where a variable with automatic // storage duration is not in scope to a point where it is in scope // is ill-formed unless the variable has scalar type, class type with // a trivial default constructor and a trivial destructor, a // cv-qualified version of one of these types, or an array of one of // the preceding types and is declared without an initializer. // C++03 [stmt.dcl.p3: // A program that jumps from a point where a local variable // with automatic storage duration is not in scope to a point // where it is in scope is ill-formed unless the variable has // POD type and is declared without an initializer. InDiag = diag::note_protected_by_variable_init; // For a variable of (array of) class type declared without an // initializer, we will have call-style initialization and the initializer // will be the CXXConstructExpr with no intervening nodes. if (const CXXConstructExpr *CCE = dyn_cast(Init)) { const CXXConstructorDecl *Ctor = CCE->getConstructor(); if (Ctor->isTrivial() && Ctor->isDefaultConstructor() && VD->getInitStyle() == VarDecl::CallInit) { if (OutDiag) InDiag = diag::note_protected_by_variable_nontriv_destructor; else if (!Ctor->getParent()->isPOD()) InDiag = diag::note_protected_by_variable_non_pod; else InDiag = 0; } } } return ScopePair(InDiag, OutDiag); } if (const TypedefNameDecl *TD = dyn_cast(D)) { if (TD->getUnderlyingType()->isVariablyModifiedType()) return ScopePair(isa(TD) ? diag::note_protected_by_vla_typedef : diag::note_protected_by_vla_type_alias, 0); } return ScopePair(0U, 0U); } /// Build scope information for a declaration that is part of a DeclStmt. void JumpScopeChecker::BuildScopeInformation(Decl *D, unsigned &ParentScope) { // If this decl causes a new scope, push and switch to it. std::pair Diags = GetDiagForGotoScopeDecl(S, D); if (Diags.first || Diags.second) { Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second, D->getLocation())); ParentScope = Scopes.size()-1; } // If the decl has an initializer, walk it with the potentially new // scope we just installed. if (VarDecl *VD = dyn_cast(D)) if (Expr *Init = VD->getInit()) BuildScopeInformation(Init, ParentScope); } /// Build scope information for a captured block literal variables. void JumpScopeChecker::BuildScopeInformation(VarDecl *D, const BlockDecl *BDecl, unsigned &ParentScope) { // exclude captured __block variables; there's no destructor // associated with the block literal for them. if (D->hasAttr()) return; QualType T = D->getType(); QualType::DestructionKind destructKind = T.isDestructedType(); if (destructKind != QualType::DK_none) { std::pair Diags; switch (destructKind) { case QualType::DK_cxx_destructor: Diags = ScopePair(diag::note_enters_block_captures_cxx_obj, diag::note_exits_block_captures_cxx_obj); break; case QualType::DK_objc_strong_lifetime: Diags = ScopePair(diag::note_enters_block_captures_strong, diag::note_exits_block_captures_strong); break; case QualType::DK_objc_weak_lifetime: Diags = ScopePair(diag::note_enters_block_captures_weak, diag::note_exits_block_captures_weak); break; case QualType::DK_nontrivial_c_struct: Diags = ScopePair(diag::note_enters_block_captures_non_trivial_c_struct, diag::note_exits_block_captures_non_trivial_c_struct); break; case QualType::DK_none: llvm_unreachable("non-lifetime captured variable"); } SourceLocation Loc = D->getLocation(); if (Loc.isInvalid()) Loc = BDecl->getLocation(); Scopes.push_back(GotoScope(ParentScope, Diags.first, Diags.second, Loc)); ParentScope = Scopes.size()-1; } } /// Build scope information for compound literals of C struct types that are /// non-trivial to destruct. void JumpScopeChecker::BuildScopeInformation(CompoundLiteralExpr *CLE, unsigned &ParentScope) { unsigned InDiag = diag::note_enters_compound_literal_scope; unsigned OutDiag = diag::note_exits_compound_literal_scope; Scopes.push_back(GotoScope(ParentScope, InDiag, OutDiag, CLE->getExprLoc())); ParentScope = Scopes.size() - 1; } /// BuildScopeInformation - The statements from CI to CE are known to form a /// coherent VLA scope with a specified parent node. Walk through the /// statements, adding any labels or gotos to LabelAndGotoScopes and recursively /// walking the AST as needed. void JumpScopeChecker::BuildScopeInformation(Stmt *S, unsigned &origParentScope) { // If this is a statement, rather than an expression, scopes within it don't // propagate out into the enclosing scope. Otherwise we have to worry // about block literals, which have the lifetime of their enclosing statement. unsigned independentParentScope = origParentScope; unsigned &ParentScope = ((isa(S) && !isa(S)) ? origParentScope : independentParentScope); unsigned StmtsToSkip = 0u; // If we found a label, remember that it is in ParentScope scope. switch (S->getStmtClass()) { case Stmt::AddrLabelExprClass: IndirectJumpTargets.push_back(cast(S)->getLabel()); break; case Stmt::ObjCForCollectionStmtClass: { auto *CS = cast(S); unsigned Diag = diag::note_protected_by_objc_fast_enumeration; unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, Diag, 0, S->getBeginLoc())); BuildScopeInformation(CS->getBody(), NewParentScope); return; } case Stmt::IndirectGotoStmtClass: // "goto *&&lbl;" is a special case which we treat as equivalent // to a normal goto. In addition, we don't calculate scope in the // operand (to avoid recording the address-of-label use), which // works only because of the restricted set of expressions which // we detect as constant targets. if (cast(S)->getConstantTarget()) { LabelAndGotoScopes[S] = ParentScope; Jumps.push_back(S); return; } LabelAndGotoScopes[S] = ParentScope; IndirectJumps.push_back(S); break; case Stmt::SwitchStmtClass: // Evaluate the C++17 init stmt and condition variable // before entering the scope of the switch statement. if (Stmt *Init = cast(S)->getInit()) { BuildScopeInformation(Init, ParentScope); ++StmtsToSkip; } if (VarDecl *Var = cast(S)->getConditionVariable()) { BuildScopeInformation(Var, ParentScope); ++StmtsToSkip; } LLVM_FALLTHROUGH; case Stmt::GotoStmtClass: // Remember both what scope a goto is in as well as the fact that we have // it. This makes the second scan not have to walk the AST again. LabelAndGotoScopes[S] = ParentScope; Jumps.push_back(S); break; case Stmt::GCCAsmStmtClass: if (auto *GS = dyn_cast(S)) if (GS->isAsmGoto()) { // Remember both what scope a goto is in as well as the fact that we // have it. This makes the second scan not have to walk the AST again. LabelAndGotoScopes[S] = ParentScope; AsmJumps.push_back(GS); for (auto *E : GS->labels()) AsmJumpTargets.push_back(E->getLabel()); } break; case Stmt::IfStmtClass: { IfStmt *IS = cast(S); if (!(IS->isConstexpr() || IS->isConsteval() || IS->isObjCAvailabilityCheck())) break; unsigned Diag = diag::note_protected_by_if_available; if (IS->isConstexpr()) Diag = diag::note_protected_by_constexpr_if; else if (IS->isConsteval()) Diag = diag::note_protected_by_consteval_if; if (VarDecl *Var = IS->getConditionVariable()) BuildScopeInformation(Var, ParentScope); // Cannot jump into the middle of the condition. unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc())); if (!IS->isConsteval()) BuildScopeInformation(IS->getCond(), NewParentScope); // Jumps into either arm of an 'if constexpr' are not allowed. NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc())); BuildScopeInformation(IS->getThen(), NewParentScope); if (Stmt *Else = IS->getElse()) { NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getBeginLoc())); BuildScopeInformation(Else, NewParentScope); } return; } case Stmt::CXXTryStmtClass: { CXXTryStmt *TS = cast(S); { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_cxx_try, diag::note_exits_cxx_try, TS->getSourceRange().getBegin())); if (Stmt *TryBlock = TS->getTryBlock()) BuildScopeInformation(TryBlock, NewParentScope); } // Jump from the catch into the try is not allowed either. for (unsigned I = 0, E = TS->getNumHandlers(); I != E; ++I) { CXXCatchStmt *CS = TS->getHandler(I); unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_cxx_catch, diag::note_exits_cxx_catch, CS->getSourceRange().getBegin())); BuildScopeInformation(CS->getHandlerBlock(), NewParentScope); } return; } case Stmt::SEHTryStmtClass: { SEHTryStmt *TS = cast(S); { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_seh_try, diag::note_exits_seh_try, TS->getSourceRange().getBegin())); if (Stmt *TryBlock = TS->getTryBlock()) BuildScopeInformation(TryBlock, NewParentScope); } // Jump from __except or __finally into the __try are not allowed either. if (SEHExceptStmt *Except = TS->getExceptHandler()) { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_seh_except, diag::note_exits_seh_except, Except->getSourceRange().getBegin())); BuildScopeInformation(Except->getBlock(), NewParentScope); } else if (SEHFinallyStmt *Finally = TS->getFinallyHandler()) { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_seh_finally, diag::note_exits_seh_finally, Finally->getSourceRange().getBegin())); BuildScopeInformation(Finally->getBlock(), NewParentScope); } return; } case Stmt::DeclStmtClass: { // If this is a declstmt with a VLA definition, it defines a scope from here // to the end of the containing context. DeclStmt *DS = cast(S); // The decl statement creates a scope if any of the decls in it are VLAs // or have the cleanup attribute. for (auto *I : DS->decls()) BuildScopeInformation(I, origParentScope); return; } case Stmt::ObjCAtTryStmtClass: { // Disallow jumps into any part of an @try statement by pushing a scope and // walking all sub-stmts in that scope. ObjCAtTryStmt *AT = cast(S); // Recursively walk the AST for the @try part. { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_objc_try, diag::note_exits_objc_try, AT->getAtTryLoc())); if (Stmt *TryPart = AT->getTryBody()) BuildScopeInformation(TryPart, NewParentScope); } // Jump from the catch to the finally or try is not valid. for (ObjCAtCatchStmt *AC : AT->catch_stmts()) { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_objc_catch, diag::note_exits_objc_catch, AC->getAtCatchLoc())); // @catches are nested and it isn't BuildScopeInformation(AC->getCatchBody(), NewParentScope); } // Jump from the finally to the try or catch is not valid. if (ObjCAtFinallyStmt *AF = AT->getFinallyStmt()) { unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_objc_finally, diag::note_exits_objc_finally, AF->getAtFinallyLoc())); BuildScopeInformation(AF, NewParentScope); } return; } case Stmt::ObjCAtSynchronizedStmtClass: { // Disallow jumps into the protected statement of an @synchronized, but // allow jumps into the object expression it protects. ObjCAtSynchronizedStmt *AS = cast(S); // Recursively walk the AST for the @synchronized object expr, it is // evaluated in the normal scope. BuildScopeInformation(AS->getSynchExpr(), ParentScope); // Recursively walk the AST for the @synchronized part, protected by a new // scope. unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_objc_synchronized, diag::note_exits_objc_synchronized, AS->getAtSynchronizedLoc())); BuildScopeInformation(AS->getSynchBody(), NewParentScope); return; } case Stmt::ObjCAutoreleasePoolStmtClass: { // Disallow jumps into the protected statement of an @autoreleasepool. ObjCAutoreleasePoolStmt *AS = cast(S); // Recursively walk the AST for the @autoreleasepool part, protected by a // new scope. unsigned NewParentScope = Scopes.size(); Scopes.push_back(GotoScope(ParentScope, diag::note_protected_by_objc_autoreleasepool, diag::note_exits_objc_autoreleasepool, AS->getAtLoc())); BuildScopeInformation(AS->getSubStmt(), NewParentScope); return; } case Stmt::ExprWithCleanupsClass: { // Disallow jumps past full-expressions that use blocks with // non-trivial cleanups of their captures. This is theoretically // implementable but a lot of work which we haven't felt up to doing. ExprWithCleanups *EWC = cast(S); for (unsigned i = 0, e = EWC->getNumObjects(); i != e; ++i) { if (auto *BDecl = EWC->getObject(i).dyn_cast()) for (const auto &CI : BDecl->captures()) { VarDecl *variable = CI.getVariable(); BuildScopeInformation(variable, BDecl, origParentScope); } else if (auto *CLE = EWC->getObject(i).dyn_cast()) BuildScopeInformation(CLE, origParentScope); else llvm_unreachable("unexpected cleanup object type"); } break; } case Stmt::MaterializeTemporaryExprClass: { // Disallow jumps out of scopes containing temporaries lifetime-extended to // automatic storage duration. MaterializeTemporaryExpr *MTE = cast(S); if (MTE->getStorageDuration() == SD_Automatic) { SmallVector CommaLHS; SmallVector Adjustments; const Expr *ExtendedObject = MTE->getSubExpr()->skipRValueSubobjectAdjustments(CommaLHS, Adjustments); if (ExtendedObject->getType().isDestructedType()) { Scopes.push_back(GotoScope(ParentScope, 0, diag::note_exits_temporary_dtor, ExtendedObject->getExprLoc())); origParentScope = Scopes.size()-1; } } break; } case Stmt::CaseStmtClass: case Stmt::DefaultStmtClass: case Stmt::LabelStmtClass: LabelAndGotoScopes[S] = ParentScope; break; case Stmt::AttributedStmtClass: { AttributedStmt *AS = cast(S); if (GetMustTailAttr(AS)) { LabelAndGotoScopes[AS] = ParentScope; MustTailStmts.push_back(AS); } break; } default: if (auto *ED = dyn_cast(S)) { if (!ED->isStandaloneDirective()) { unsigned NewParentScope = Scopes.size(); Scopes.emplace_back(ParentScope, diag::note_omp_protected_structured_block, diag::note_omp_exits_structured_block, ED->getStructuredBlock()->getBeginLoc()); BuildScopeInformation(ED->getStructuredBlock(), NewParentScope); return; } } break; } for (Stmt *SubStmt : S->children()) { if (!SubStmt) continue; if (StmtsToSkip) { --StmtsToSkip; continue; } // Cases, labels, and defaults aren't "scope parents". It's also // important to handle these iteratively instead of recursively in // order to avoid blowing out the stack. while (true) { Stmt *Next; if (SwitchCase *SC = dyn_cast(SubStmt)) Next = SC->getSubStmt(); else if (LabelStmt *LS = dyn_cast(SubStmt)) Next = LS->getSubStmt(); else break; LabelAndGotoScopes[SubStmt] = ParentScope; SubStmt = Next; } // Recursively walk the AST. BuildScopeInformation(SubStmt, ParentScope); } } /// VerifyJumps - Verify each element of the Jumps array to see if they are /// valid, emitting diagnostics if not. void JumpScopeChecker::VerifyJumps() { while (!Jumps.empty()) { Stmt *Jump = Jumps.pop_back_val(); // With a goto, if (GotoStmt *GS = dyn_cast(Jump)) { // The label may not have a statement if it's coming from inline MS ASM. if (GS->getLabel()->getStmt()) { CheckJump(GS, GS->getLabel()->getStmt(), GS->getGotoLoc(), diag::err_goto_into_protected_scope, diag::ext_goto_into_protected_scope, diag::warn_cxx98_compat_goto_into_protected_scope); } CheckGotoStmt(GS); continue; } // We only get indirect gotos here when they have a constant target. if (IndirectGotoStmt *IGS = dyn_cast(Jump)) { LabelDecl *Target = IGS->getConstantTarget(); CheckJump(IGS, Target->getStmt(), IGS->getGotoLoc(), diag::err_goto_into_protected_scope, diag::ext_goto_into_protected_scope, diag::warn_cxx98_compat_goto_into_protected_scope); continue; } SwitchStmt *SS = cast(Jump); for (SwitchCase *SC = SS->getSwitchCaseList(); SC; SC = SC->getNextSwitchCase()) { if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(SC))) continue; SourceLocation Loc; if (CaseStmt *CS = dyn_cast(SC)) Loc = CS->getBeginLoc(); else if (DefaultStmt *DS = dyn_cast(SC)) Loc = DS->getBeginLoc(); else Loc = SC->getBeginLoc(); CheckJump(SS, SC, Loc, diag::err_switch_into_protected_scope, 0, diag::warn_cxx98_compat_switch_into_protected_scope); } } } /// VerifyIndirectOrAsmJumps - Verify whether any possible indirect goto or /// asm goto jump might cross a protection boundary. Unlike direct jumps, /// indirect or asm goto jumps count cleanups as protection boundaries: /// since there's no way to know where the jump is going, we can't implicitly /// run the right cleanups the way we can with direct jumps. /// Thus, an indirect/asm jump is "trivial" if it bypasses no /// initializations and no teardowns. More formally, an indirect/asm jump /// from A to B is trivial if the path out from A to DCA(A,B) is /// trivial and the path in from DCA(A,B) to B is trivial, where /// DCA(A,B) is the deepest common ancestor of A and B. /// Jump-triviality is transitive but asymmetric. /// /// A path in is trivial if none of the entered scopes have an InDiag. /// A path out is trivial is none of the exited scopes have an OutDiag. /// /// Under these definitions, this function checks that the indirect /// jump between A and B is trivial for every indirect goto statement A /// and every label B whose address was taken in the function. void JumpScopeChecker::VerifyIndirectOrAsmJumps(bool IsAsmGoto) { SmallVector GotoJumps = IsAsmGoto ? AsmJumps : IndirectJumps; if (GotoJumps.empty()) return; SmallVector JumpTargets = IsAsmGoto ? AsmJumpTargets : IndirectJumpTargets; // If there aren't any address-of-label expressions in this function, // complain about the first indirect goto. if (JumpTargets.empty()) { assert(!IsAsmGoto &&"only indirect goto can get here"); S.Diag(GotoJumps[0]->getBeginLoc(), diag::err_indirect_goto_without_addrlabel); return; } // Collect a single representative of every scope containing an // indirect or asm goto. For most code bases, this substantially cuts // down on the number of jump sites we'll have to consider later. typedef std::pair JumpScope; SmallVector JumpScopes; { llvm::DenseMap JumpScopesMap; for (SmallVectorImpl::iterator I = GotoJumps.begin(), E = GotoJumps.end(); I != E; ++I) { Stmt *IG = *I; if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(IG))) continue; unsigned IGScope = LabelAndGotoScopes[IG]; Stmt *&Entry = JumpScopesMap[IGScope]; if (!Entry) Entry = IG; } JumpScopes.reserve(JumpScopesMap.size()); for (llvm::DenseMap::iterator I = JumpScopesMap.begin(), E = JumpScopesMap.end(); I != E; ++I) JumpScopes.push_back(*I); } // Collect a single representative of every scope containing a // label whose address was taken somewhere in the function. // For most code bases, there will be only one such scope. llvm::DenseMap TargetScopes; for (SmallVectorImpl::iterator I = JumpTargets.begin(), E = JumpTargets.end(); I != E; ++I) { LabelDecl *TheLabel = *I; if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(TheLabel->getStmt()))) continue; unsigned LabelScope = LabelAndGotoScopes[TheLabel->getStmt()]; LabelDecl *&Target = TargetScopes[LabelScope]; if (!Target) Target = TheLabel; } // For each target scope, make sure it's trivially reachable from // every scope containing a jump site. // // A path between scopes always consists of exitting zero or more // scopes, then entering zero or more scopes. We build a set of // of scopes S from which the target scope can be trivially // entered, then verify that every jump scope can be trivially // exitted to reach a scope in S. llvm::BitVector Reachable(Scopes.size(), false); for (llvm::DenseMap::iterator TI = TargetScopes.begin(), TE = TargetScopes.end(); TI != TE; ++TI) { unsigned TargetScope = TI->first; LabelDecl *TargetLabel = TI->second; Reachable.reset(); // Mark all the enclosing scopes from which you can safely jump // into the target scope. 'Min' will end up being the index of // the shallowest such scope. unsigned Min = TargetScope; while (true) { Reachable.set(Min); // Don't go beyond the outermost scope. if (Min == 0) break; // Stop if we can't trivially enter the current scope. if (Scopes[Min].InDiag) break; Min = Scopes[Min].ParentScope; } // Walk through all the jump sites, checking that they can trivially // reach this label scope. for (SmallVectorImpl::iterator I = JumpScopes.begin(), E = JumpScopes.end(); I != E; ++I) { unsigned Scope = I->first; // Walk out the "scope chain" for this scope, looking for a scope // we've marked reachable. For well-formed code this amortizes // to O(JumpScopes.size() / Scopes.size()): we only iterate // when we see something unmarked, and in well-formed code we // mark everything we iterate past. bool IsReachable = false; while (true) { if (Reachable.test(Scope)) { // If we find something reachable, mark all the scopes we just // walked through as reachable. for (unsigned S = I->first; S != Scope; S = Scopes[S].ParentScope) Reachable.set(S); IsReachable = true; break; } // Don't walk out if we've reached the top-level scope or we've // gotten shallower than the shallowest reachable scope. if (Scope == 0 || Scope < Min) break; // Don't walk out through an out-diagnostic. if (Scopes[Scope].OutDiag) break; Scope = Scopes[Scope].ParentScope; } // Only diagnose if we didn't find something. if (IsReachable) continue; DiagnoseIndirectOrAsmJump(I->second, I->first, TargetLabel, TargetScope); } } } /// Return true if a particular error+note combination must be downgraded to a /// warning in Microsoft mode. static bool IsMicrosoftJumpWarning(unsigned JumpDiag, unsigned InDiagNote) { return (JumpDiag == diag::err_goto_into_protected_scope && (InDiagNote == diag::note_protected_by_variable_init || InDiagNote == diag::note_protected_by_variable_nontriv_destructor)); } /// Return true if a particular note should be downgraded to a compatibility /// warning in C++11 mode. static bool IsCXX98CompatWarning(Sema &S, unsigned InDiagNote) { return S.getLangOpts().CPlusPlus11 && InDiagNote == diag::note_protected_by_variable_non_pod; } /// Produce primary diagnostic for an indirect jump statement. static void DiagnoseIndirectOrAsmJumpStmt(Sema &S, Stmt *Jump, LabelDecl *Target, bool &Diagnosed) { if (Diagnosed) return; bool IsAsmGoto = isa(Jump); S.Diag(Jump->getBeginLoc(), diag::err_indirect_goto_in_protected_scope) << IsAsmGoto; S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target) << IsAsmGoto; Diagnosed = true; } /// Produce note diagnostics for a jump into a protected scope. void JumpScopeChecker::NoteJumpIntoScopes(ArrayRef ToScopes) { if (CHECK_PERMISSIVE(ToScopes.empty())) return; for (unsigned I = 0, E = ToScopes.size(); I != E; ++I) if (Scopes[ToScopes[I]].InDiag) S.Diag(Scopes[ToScopes[I]].Loc, Scopes[ToScopes[I]].InDiag); } /// Diagnose an indirect jump which is known to cross scopes. void JumpScopeChecker::DiagnoseIndirectOrAsmJump(Stmt *Jump, unsigned JumpScope, LabelDecl *Target, unsigned TargetScope) { if (CHECK_PERMISSIVE(JumpScope == TargetScope)) return; unsigned Common = GetDeepestCommonScope(JumpScope, TargetScope); bool Diagnosed = false; // Walk out the scope chain until we reach the common ancestor. for (unsigned I = JumpScope; I != Common; I = Scopes[I].ParentScope) if (Scopes[I].OutDiag) { DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed); S.Diag(Scopes[I].Loc, Scopes[I].OutDiag); } SmallVector ToScopesCXX98Compat; // Now walk into the scopes containing the label whose address was taken. for (unsigned I = TargetScope; I != Common; I = Scopes[I].ParentScope) if (IsCXX98CompatWarning(S, Scopes[I].InDiag)) ToScopesCXX98Compat.push_back(I); else if (Scopes[I].InDiag) { DiagnoseIndirectOrAsmJumpStmt(S, Jump, Target, Diagnosed); S.Diag(Scopes[I].Loc, Scopes[I].InDiag); } // Diagnose this jump if it would be ill-formed in C++98. if (!Diagnosed && !ToScopesCXX98Compat.empty()) { bool IsAsmGoto = isa(Jump); S.Diag(Jump->getBeginLoc(), diag::warn_cxx98_compat_indirect_goto_in_protected_scope) << IsAsmGoto; S.Diag(Target->getStmt()->getIdentLoc(), diag::note_indirect_goto_target) << IsAsmGoto; NoteJumpIntoScopes(ToScopesCXX98Compat); } } /// CheckJump - Validate that the specified jump statement is valid: that it is /// jumping within or out of its current scope, not into a deeper one. void JumpScopeChecker::CheckJump(Stmt *From, Stmt *To, SourceLocation DiagLoc, unsigned JumpDiagError, unsigned JumpDiagWarning, unsigned JumpDiagCXX98Compat) { if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(From))) return; if (CHECK_PERMISSIVE(!LabelAndGotoScopes.count(To))) return; unsigned FromScope = LabelAndGotoScopes[From]; unsigned ToScope = LabelAndGotoScopes[To]; // Common case: exactly the same scope, which is fine. if (FromScope == ToScope) return; // Warn on gotos out of __finally blocks. if (isa(From) || isa(From)) { // If FromScope > ToScope, FromScope is more nested and the jump goes to a // less nested scope. Check if it crosses a __finally along the way. for (unsigned I = FromScope; I > ToScope; I = Scopes[I].ParentScope) { if (Scopes[I].InDiag == diag::note_protected_by_seh_finally) { S.Diag(From->getBeginLoc(), diag::warn_jump_out_of_seh_finally); break; } if (Scopes[I].InDiag == diag::note_omp_protected_structured_block) { S.Diag(From->getBeginLoc(), diag::err_goto_into_protected_scope); S.Diag(To->getBeginLoc(), diag::note_omp_exits_structured_block); break; } } } unsigned CommonScope = GetDeepestCommonScope(FromScope, ToScope); // It's okay to jump out from a nested scope. if (CommonScope == ToScope) return; // Pull out (and reverse) any scopes we might need to diagnose skipping. SmallVector ToScopesCXX98Compat; SmallVector ToScopesError; SmallVector ToScopesWarning; for (unsigned I = ToScope; I != CommonScope; I = Scopes[I].ParentScope) { if (S.getLangOpts().MSVCCompat && JumpDiagWarning != 0 && IsMicrosoftJumpWarning(JumpDiagError, Scopes[I].InDiag)) ToScopesWarning.push_back(I); else if (IsCXX98CompatWarning(S, Scopes[I].InDiag)) ToScopesCXX98Compat.push_back(I); else if (Scopes[I].InDiag) ToScopesError.push_back(I); } // Handle warnings. if (!ToScopesWarning.empty()) { S.Diag(DiagLoc, JumpDiagWarning); NoteJumpIntoScopes(ToScopesWarning); assert(isa(To)); LabelStmt *Label = cast(To); Label->setSideEntry(true); } // Handle errors. if (!ToScopesError.empty()) { S.Diag(DiagLoc, JumpDiagError); NoteJumpIntoScopes(ToScopesError); } // Handle -Wc++98-compat warnings if the jump is well-formed. if (ToScopesError.empty() && !ToScopesCXX98Compat.empty()) { S.Diag(DiagLoc, JumpDiagCXX98Compat); NoteJumpIntoScopes(ToScopesCXX98Compat); } } void JumpScopeChecker::CheckGotoStmt(GotoStmt *GS) { if (GS->getLabel()->isMSAsmLabel()) { S.Diag(GS->getGotoLoc(), diag::err_goto_ms_asm_label) << GS->getLabel()->getIdentifier(); S.Diag(GS->getLabel()->getLocation(), diag::note_goto_ms_asm_label) << GS->getLabel()->getIdentifier(); } } void JumpScopeChecker::VerifyMustTailStmts() { for (AttributedStmt *AS : MustTailStmts) { for (unsigned I = LabelAndGotoScopes[AS]; I; I = Scopes[I].ParentScope) { if (Scopes[I].OutDiag) { S.Diag(AS->getBeginLoc(), diag::err_musttail_scope); S.Diag(Scopes[I].Loc, Scopes[I].OutDiag); } } } } const Attr *JumpScopeChecker::GetMustTailAttr(AttributedStmt *AS) { ArrayRef Attrs = AS->getAttrs(); const auto *Iter = llvm::find_if(Attrs, [](const Attr *A) { return isa(A); }); return Iter != Attrs.end() ? *Iter : nullptr; } void Sema::DiagnoseInvalidJumps(Stmt *Body) { (void)JumpScopeChecker(Body, *this); }