On Tue, Aug 23, 2016 at 4:11 AM, Roger Ferrer Ibanez via cfe-commits <cfe-commits@lists.llvm.org> wrote: > Yes it was approved on IRC by Aaron Ballman:
Sorry for not mentioning this on the mailing list as well as in IRC! ~Aaron > > > > T 1470758009 <rogfer01> zygoloid: do you have any further thoughts about > https://reviews.llvm.org/D20561 ? thank you very much :) > > T 1470758207 <AaronBallman> rogfer01: if zygoloid doesn't review in the > next two days, you can go ahead and commit. I've accepted it, and Richard's > comments suggest you're following the correct approach with your latest > patch. If there are problems, we can always revert again if needed > > > > Kind regards, > > Roger > > > > From: tha...@google.com [mailto:tha...@google.com] On Behalf Of Nico Weber > Sent: 22 August 2016 17:59 > To: Roger Ferrer Ibanez > Cc: cfe-commits > Subject: Re: r278483 - This patch implements PR#22821. > > > > I don't see any approval after Aaron's "Please wait until someone has had > the chance to review before committing" on https://reviews.llvm.org/D20561 > -- was this reviewed on IRC? > > > > On Fri, Aug 12, 2016 at 4:04 AM, Roger Ferrer Ibanez via cfe-commits > <cfe-commits@lists.llvm.org> wrote: > > Author: rogfer01 > Date: Fri Aug 12 03:04:13 2016 > New Revision: 278483 > > URL: http://llvm.org/viewvc/llvm-project?rev=278483&view=rev > Log: > This patch implements PR#22821. > > Taking the address of a packed member is dangerous since the reduced > alignment of the pointee is lost. This can lead to memory alignment > faults in some architectures if the pointer value is dereferenced. > > This change adds a new warning to clang emitted when taking the address > of a packed member. A packed member is either a field/data member > declared as attribute((packed)) or belonging to a struct/class > declared as such. The associated flag is -Waddress-of-packed-member. > Conversions (either implicit or via a valid casting) to pointer types > with lower or equal alignment requirements (e.g. void* or char*) > will silence the warning. > > Differential Revision: https://reviews.llvm.org/D20561 > > > > Modified: > cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > cfe/trunk/include/clang/Sema/Sema.h > cfe/trunk/lib/Sema/SemaCast.cpp > cfe/trunk/lib/Sema/SemaChecking.cpp > cfe/trunk/lib/Sema/SemaExpr.cpp > cfe/trunk/lib/Sema/SemaInit.cpp > > Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original) > +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Fri Aug 12 03:04:13 > 2016 > @@ -5489,6 +5489,9 @@ def warn_pointer_indirection_from_incomp > "dereference of type %1 that was reinterpret_cast from type %0 has > undefined " > "behavior">, > InGroup<UndefinedReinterpretCast>, DefaultIgnore; > +def warn_taking_address_of_packed_member : Warning< > + "taking address of packed member %0 of class or structure %q1 may result > in an unaligned pointer value">, > + InGroup<DiagGroup<"address-of-packed-member">>; > > def err_objc_object_assignment : Error< > "cannot assign to class object (%0 invalid)">; > > Modified: cfe/trunk/include/clang/Sema/Sema.h > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/include/clang/Sema/Sema.h (original) > +++ cfe/trunk/include/clang/Sema/Sema.h Fri Aug 12 03:04:13 2016 > @@ -9570,6 +9570,10 @@ private: > void CheckArgumentWithTypeTag(const ArgumentWithTypeTagAttr *Attr, > const Expr * const *ExprArgs); > > + /// \brief Check if we are taking the address of a packed field > + /// as this may be a problem if the pointer value is dereferenced. > + void CheckAddressOfPackedMember(Expr *rhs); > + > /// \brief The parser's current scope. > /// > /// The parser maintains this state here. > @@ -9664,6 +9668,51 @@ public: > // Emitting members of dllexported classes is delayed until the class > // (including field initializers) is fully parsed. > SmallVector<CXXRecordDecl*, 4> DelayedDllExportClasses; > + > +private: > + /// \brief Helper class that collects misaligned member designations and > + /// their location info for delayed diagnostics. > + struct MisalignedMember { > + Expr *E; > + RecordDecl *RD; > + ValueDecl *MD; > + CharUnits Alignment; > + > + MisalignedMember() : E(), RD(), MD(), Alignment() {} > + MisalignedMember(Expr *E, RecordDecl *RD, ValueDecl *MD, > + CharUnits Alignment) > + : E(E), RD(RD), MD(MD), Alignment(Alignment) {} > + explicit MisalignedMember(Expr *E) > + : MisalignedMember(E, nullptr, nullptr, CharUnits()) {} > + > + bool operator==(const MisalignedMember &m) { return this->E == m.E; } > + }; > + /// \brief Small set of gathered accesses to potentially misaligned > members > + /// due to the packed attribute. > + SmallVector<MisalignedMember, 4> MisalignedMembers; > + > + /// \brief Adds an expression to the set of gathered misaligned members. > + void AddPotentialMisalignedMembers(Expr *E, RecordDecl *RD, ValueDecl > *MD, > + CharUnits Alignment); > + > +public: > + /// \brief Diagnoses the current set of gathered accesses. This typically > + /// happens at full expression level. The set is cleared after emitting > the > + /// diagnostics. > + void DiagnoseMisalignedMembers(); > + > + /// \brief This function checks if the expression is in the sef of > potentially > + /// misaligned members and it is converted to some pointer type T with > lower > + /// or equal alignment requirements. If so it removes it. This is used > when > + /// we do not want to diagnose such misaligned access (e.g. in > conversions to void*). > + void DiscardMisalignedMemberAddress(const Type *T, Expr *E); > + > + /// \brief This function calls Action when it determines that E > designates a > + /// misaligned member due to the packed attribute. This is used to emit > + /// local diagnostics like in reference binding. > + void RefersToMemberWithReducedAlignment( > + Expr *E, > + std::function<void(Expr *, RecordDecl *, ValueDecl *, CharUnits)> > Action); > }; > > /// \brief RAII object that enters a new expression evaluation context. > > Modified: cfe/trunk/lib/Sema/SemaCast.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCast.cpp?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/lib/Sema/SemaCast.cpp (original) > +++ cfe/trunk/lib/Sema/SemaCast.cpp Fri Aug 12 03:04:13 2016 > @@ -256,6 +256,7 @@ Sema::BuildCXXNamedCast(SourceLocation O > Op.CheckConstCast(); > if (Op.SrcExpr.isInvalid()) > return ExprError(); > + DiscardMisalignedMemberAddress(DestType.getTypePtr(), E); > } > return Op.complete(CXXConstCastExpr::Create(Context, Op.ResultType, > Op.ValueKind, Op.SrcExpr.get(), > DestTInfo, > @@ -279,6 +280,7 @@ Sema::BuildCXXNamedCast(SourceLocation O > Op.CheckReinterpretCast(); > if (Op.SrcExpr.isInvalid()) > return ExprError(); > + DiscardMisalignedMemberAddress(DestType.getTypePtr(), E); > } > return Op.complete(CXXReinterpretCastExpr::Create(Context, > Op.ResultType, > Op.ValueKind, Op.Kind, > Op.SrcExpr.get(), > @@ -291,6 +293,7 @@ Sema::BuildCXXNamedCast(SourceLocation O > Op.CheckStaticCast(); > if (Op.SrcExpr.isInvalid()) > return ExprError(); > + DiscardMisalignedMemberAddress(DestType.getTypePtr(), E); > } > > return Op.complete(CXXStaticCastExpr::Create(Context, Op.ResultType, > > Modified: cfe/trunk/lib/Sema/SemaChecking.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/lib/Sema/SemaChecking.cpp (original) > +++ cfe/trunk/lib/Sema/SemaChecking.cpp Fri Aug 12 03:04:13 2016 > @@ -8383,6 +8383,8 @@ void CheckImplicitConversion(Sema &S, Ex > > DiagnoseNullConversion(S, E, T, CC); > > + S.DiscardMisalignedMemberAddress(Target, E); > + > if (!Source->isIntegerType() || !Target->isIntegerType()) > return; > > @@ -9453,6 +9455,7 @@ void Sema::CheckCompletedExpr(Expr *E, S > CheckUnsequencedOperations(E); > if (!IsConstexpr && !E->isValueDependent()) > CheckForIntOverflow(E); > + DiagnoseMisalignedMembers(); > } > > void Sema::CheckBitFieldInitialization(SourceLocation InitLoc, > @@ -10998,3 +11001,67 @@ void Sema::CheckArgumentWithTypeTag(cons > << ArgumentExpr->getSourceRange() > << TypeTagExpr->getSourceRange(); > } > + > +void Sema::AddPotentialMisalignedMembers(Expr *E, RecordDecl *RD, ValueDecl > *MD, > + CharUnits Alignment) { > + MisalignedMembers.emplace_back(E, RD, MD, Alignment); > +} > + > +void Sema::DiagnoseMisalignedMembers() { > + for (MisalignedMember &m : MisalignedMembers) { > + Diag(m.E->getLocStart(), diag::warn_taking_address_of_packed_member) > + << m.MD << m.RD << m.E->getSourceRange(); > + } > + MisalignedMembers.clear(); > +} > + > +void Sema::DiscardMisalignedMemberAddress(const Type *T, Expr *E) { > + if (!T->isPointerType()) > + return; > + if (isa<UnaryOperator>(E) && > + cast<UnaryOperator>(E)->getOpcode() == UO_AddrOf) { > + auto *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); > + if (isa<MemberExpr>(Op)) { > + auto MA = std::find(MisalignedMembers.begin(), > MisalignedMembers.end(), > + MisalignedMember(Op)); > + if (MA != MisalignedMembers.end() && > + Context.getTypeAlignInChars(T->getPointeeType()) <= > MA->Alignment) > + MisalignedMembers.erase(MA); > + } > + } > +} > + > +void Sema::RefersToMemberWithReducedAlignment( > + Expr *E, > + std::function<void(Expr *, RecordDecl *, ValueDecl *, CharUnits)> > Action) { > + const auto *ME = dyn_cast<MemberExpr>(E); > + while (ME && isa<FieldDecl>(ME->getMemberDecl())) { > + QualType BaseType = ME->getBase()->getType(); > + if (ME->isArrow()) > + BaseType = BaseType->getPointeeType(); > + RecordDecl *RD = BaseType->getAs<RecordType>()->getDecl(); > + > + ValueDecl *MD = ME->getMemberDecl(); > + bool ByteAligned = Context.getTypeAlignInChars(MD->getType()).isOne(); > + if (ByteAligned) // Attribute packed does not have any effect. > + break; > + > + if (!ByteAligned && > + (RD->hasAttr<PackedAttr>() || (MD->hasAttr<PackedAttr>()))) { > + CharUnits Alignment = > std::min(Context.getTypeAlignInChars(MD->getType()), > + > Context.getTypeAlignInChars(BaseType)); > + // Notify that this expression designates a member with reduced > alignment > + Action(E, RD, MD, Alignment); > + break; > + } > + ME = dyn_cast<MemberExpr>(ME->getBase()); > + } > +} > + > +void Sema::CheckAddressOfPackedMember(Expr *rhs) { > + using namespace std::placeholders; > + RefersToMemberWithReducedAlignment( > + rhs, std::bind(&Sema::AddPotentialMisalignedMembers, std::ref(*this), > _1, > + _2, _3, _4)); > +} > + > > Modified: cfe/trunk/lib/Sema/SemaExpr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/lib/Sema/SemaExpr.cpp (original) > +++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Aug 12 03:04:13 2016 > @@ -6022,7 +6022,9 @@ Sema::ActOnCastExpr(Scope *S, SourceLoca > CheckTollFreeBridgeCast(castType, CastExpr); > > CheckObjCBridgeRelatedCast(castType, CastExpr); > - > + > + DiscardMisalignedMemberAddress(castType.getTypePtr(), CastExpr); > + > return BuildCStyleCastExpr(LParenLoc, castTInfo, RParenLoc, CastExpr); > } > > @@ -10614,6 +10616,8 @@ QualType Sema::CheckAddressOfOperand(Exp > if (op->getType()->isObjCObjectType()) > return Context.getObjCObjectPointerType(op->getType()); > > + CheckAddressOfPackedMember(op); > + > return Context.getPointerType(op->getType()); > } > > > Modified: cfe/trunk/lib/Sema/SemaInit.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=278483&r1=278482&r2=278483&view=diff > ============================================================================== > --- cfe/trunk/lib/Sema/SemaInit.cpp (original) > +++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Aug 12 03:04:13 2016 > @@ -6660,12 +6660,16 @@ InitializationSequence::Perform(Sema &S, > getAssignmentAction(Entity), CCK); > if (CurInitExprRes.isInvalid()) > return ExprError(); > + > + S.DiscardMisalignedMemberAddress(Step->Type.getTypePtr(), > CurInit.get()); > + > CurInit = CurInitExprRes; > > if (Step->Kind == SK_ConversionSequenceNoNarrowing && > S.getLangOpts().CPlusPlus && !CurInit.get()->isValueDependent()) > DiagnoseNarrowingInInitList(S, *Step->ICS, SourceType, > Entity.getType(), > CurInit.get()); > + > break; > } > > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits > > > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits > _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
