r275417 - Diagnose taking address and reference binding of packed members

Nico Weber via cfe-commits cfe-commits at lists.llvm.org
Thu Jul 14 14:43:19 PDT 2016


I mean clang's diagnostic could say this too. For example, it could have a
note pointing at the attribute(packed) saying "struct alignment set to 1
here" or some such.

On Thu, Jul 14, 2016 at 5:25 PM, Roger Ferrer Ibanez <
Roger.FerrerIbanez at arm.com> wrote:

> Hi Nico,
>
>
> yes, it should be clearly stated in the documentation. I will try to find
> some time to contribute a change in the docs.
>
>
> I forgot that fact in my first answer to your original question. So, I
> think that the warning should fire in this case. Actually, I analysed
> precisely this case in phabricator and there was some consensus in that the
> warning was sensible.
>
>
> Kind regards,
>
> Roger
>
>
> ------------------------------
> *From:* thakis at google.com <thakis at google.com> on behalf of Nico Weber <
> thakis at chromium.org>
> *Sent:* 14 July 2016 22:14:10
> *To:* Richard Smith
> *Cc:* Roger Ferrer Ibanez; cfe-commits
> *Subject:* Re: r275417 - Diagnose taking address and reference binding of
> packed members
>
> On Thu, Jul 14, 2016 at 5:07 PM, Richard Smith <richard at metafoo.co.uk>
> wrote:
>
>> On Thu, Jul 14, 2016 at 10:15 AM, Nico Weber via cfe-commits <
>> cfe-commits at lists.llvm.org> wrote:
>>
>>> Hi,
>>>
>>> this fires on (at least) usrsctplib [1]:
>>>
>>> FAILED: obj/third_party/usrsctp/usrsctp/sctp_input.o
>>> ../../third_party/usrsctp/usrsctplib/usrsctplib/netinet/sctp_input.c:1708:15:
>>> error: taking address of packed member 'time_entered' of class or structure
>>> 'sctp_state_cookie' may result in an unaligned pointer value
>>> [-Werror,-Waddress-of-packed-member]
>>>
>>> &cookie->time_entered,
>>>
>>>  ^~~~~~~~~~~~~~~~~~~~
>>> ../../third_party/usrsctp/usrsctplib/usrsctplib/netinet/sctp_input.c:2458:10:
>>> error: taking address of packed member 'time_entered' of class or structure
>>> 'sctp_state_cookie' may result in an unaligned pointer value
>>> [-Werror,-Waddress-of-packed-member]
>>>                                                   &cookie->time_entered,
>>> sctp_align_unsafe_makecopy,
>>>                                                    ^~~~~~~~~~~~~~~~~~~~
>>> 2 errors generated.
>>>
>>> The struct looks like so [2]:
>>>
>>> struct sctp_state_cookie { /* this is our definition... */
>>> uint8_t identification[SCTP_IDENTIFICATION_SIZE];/* id of who we are */
>>> struct timeval time_entered; /* the time I built cookie */
>>>   ...
>>>
>>> The _SIZE is 16, so as long as sctp_state_cookie is aligned, that field
>>> should be aligned as well, right? And while the struct is packed, its
>>> alignment isn't overwritten (unless the packed attribute does that too, but
>>> the docs at least don't mention that).
>>>
>>
>> The packed attribute does that too.
>>
>> struct __attribute__((packed)) X {
>>   unsigned long long a;
>> };
>> static_assert(alignof(X) == 1, ""); // does not fire
>>
>> What __attribute__((packed)) really means is that the minimum alignment
>> is reduced to 1.
>>
>
> Wow, that's pretty surprising! Maybe the warning text could be more
> explicit about this.
>
>
>>
>>
>>> Should the warning really fire here?
>>>
>>> 1:
>>> https://build.chromium.org/p/chromium.fyi/builders/ClangToTLinux/builds/5748/steps/compile/logs/stdio
>>> 2:
>>> https://cs.chromium.org/chromium/src/third_party/usrsctp/usrsctplib/usrsctplib/netinet/sctp_header.h?sq=package:chromium&dr=C&rcl=1468495044&l=190
>>>
>>> On Thu, Jul 14, 2016 at 10:10 AM, Roger Ferrer Ibanez via cfe-commits <
>>> cfe-commits at lists.llvm.org> wrote:
>>>
>>>> Author: rogfer01
>>>> Date: Thu Jul 14 09:10:43 2016
>>>> New Revision: 275417
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=275417&view=rev
>>>> Log:
>>>> Diagnose taking address and reference binding of packed members
>>>>
>>>> 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*)
>>>> silence the warning.
>>>>
>>>> This change also adds a new error diagnostic when the user attempts to
>>>> bind a reference to a packed member, regardless of the alignment.
>>>>
>>>> Differential Revision: https://reviews.llvm.org/D20561
>>>>
>>>>
>>>>
>>>> Added:
>>>>     cfe/trunk/test/Sema/address-packed-member-memops.c
>>>>     cfe/trunk/test/Sema/address-packed.c
>>>>     cfe/trunk/test/SemaCXX/address-packed-member-memops.cpp
>>>>     cfe/trunk/test/SemaCXX/address-packed.cpp
>>>> 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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Thu Jul 14
>>>> 09:10:43 2016
>>>> @@ -5425,6 +5425,11 @@ 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_binding_reference_to_packed_member : Error<
>>>> +  "binding reference to packed member %0 of class or structure %q1">;
>>>>
>>>>  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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Sema/Sema.h (original)
>>>> +++ cfe/trunk/include/clang/Sema/Sema.h Thu Jul 14 09:10:43 2016
>>>> @@ -9518,6 +9518,10 @@ 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.
>>>> @@ -9596,6 +9600,51 @@ 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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaCast.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaCast.cpp Thu Jul 14 09:10:43 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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaChecking.cpp Thu Jul 14 09:10:43 2016
>>>> @@ -8302,6 +8302,8 @@ void CheckImplicitConversion(Sema &S, Ex
>>>>
>>>>    DiagnoseNullConversion(S, E, T, CC);
>>>>
>>>> +  S.DiscardMisalignedMemberAddress(Target, E);
>>>> +
>>>>    if (!Source->isIntegerType() || !Target->isIntegerType())
>>>>      return;
>>>>
>>>> @@ -9371,6 +9373,7 @@ void Sema::CheckCompletedExpr(Expr *E, S
>>>>    CheckUnsequencedOperations(E);
>>>>    if (!IsConstexpr && !E->isValueDependent())
>>>>      CheckForIntOverflow(E);
>>>> +  DiagnoseMisalignedMembers();
>>>>  }
>>>>
>>>>  void Sema::CheckBitFieldInitialization(SourceLocation InitLoc,
>>>> @@ -10916,3 +10919,67 @@ 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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Thu Jul 14 09:10:43 2016
>>>> @@ -6001,7 +6001,9 @@ Sema::ActOnCastExpr(Scope *S, SourceLoca
>>>>    CheckTollFreeBridgeCast(castType, CastExpr);
>>>>
>>>>    CheckObjCBridgeRelatedCast(castType, CastExpr);
>>>> -
>>>> +
>>>> +  DiscardMisalignedMemberAddress(castType.getTypePtr(), CastExpr);
>>>> +
>>>>    return BuildCStyleCastExpr(LParenLoc, castTInfo, RParenLoc,
>>>> CastExpr);
>>>>  }
>>>>
>>>> @@ -10534,6 +10536,8 @@ 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=275417&r1=275416&r2=275417&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaInit.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaInit.cpp Thu Jul 14 09:10:43 2016
>>>> @@ -6457,6 +6457,15 @@ InitializationSequence::Perform(Sema &S,
>>>>                                    ExtendingEntity->getDecl());
>>>>
>>>>        CheckForNullPointerDereference(S, CurInit.get());
>>>> +
>>>> +      S.RefersToMemberWithReducedAlignment(CurInit.get(), [&](Expr *E,
>>>> +
>>>> RecordDecl *RD,
>>>> +
>>>> ValueDecl *MD,
>>>> +
>>>> CharUnits) {
>>>> +        S.Diag(Kind.getLocation(),
>>>> diag::err_binding_reference_to_packed_member)
>>>> +            << MD << RD << E->getSourceRange();
>>>> +      });
>>>> +
>>>>        break;
>>>>
>>>>      case SK_BindReferenceToTemporary: {
>>>> @@ -6645,12 +6654,16 @@ 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;
>>>>      }
>>>>
>>>>
>>>> Added: cfe/trunk/test/Sema/address-packed-member-memops.c
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/address-packed-member-memops.c?rev=275417&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Sema/address-packed-member-memops.c (added)
>>>> +++ cfe/trunk/test/Sema/address-packed-member-memops.c Thu Jul 14
>>>> 09:10:43 2016
>>>> @@ -0,0 +1,26 @@
>>>> +// RUN: %clang_cc1 -fsyntax-only -verify %s
>>>> +// expected-no-diagnostics
>>>> +
>>>> +struct B {
>>>> +  int x, y, z, w;
>>>> +} b;
>>>> +
>>>> +struct __attribute__((packed)) A {
>>>> +  struct B b;
>>>> +} a;
>>>> +
>>>> +typedef __typeof__(sizeof(int)) size_t;
>>>> +
>>>> +void *memcpy(void *dest, const void *src, size_t n);
>>>> +int memcmp(const void *s1, const void *s2, size_t n);
>>>> +void *memmove(void *dest, const void *src, size_t n);
>>>> +void *memset(void *s, int c, size_t n);
>>>> +
>>>> +int x;
>>>> +
>>>> +void foo(void) {
>>>> +  memcpy(&a.b, &b, sizeof(b));
>>>> +  memmove(&a.b, &b, sizeof(b));
>>>> +  memset(&a.b, 0, sizeof(b));
>>>> +  x = memcmp(&a.b, &b, sizeof(b));
>>>> +}
>>>>
>>>> Added: cfe/trunk/test/Sema/address-packed.c
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/address-packed.c?rev=275417&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Sema/address-packed.c (added)
>>>> +++ cfe/trunk/test/Sema/address-packed.c Thu Jul 14 09:10:43 2016
>>>> @@ -0,0 +1,160 @@
>>>> +// RUN: %clang_cc1 -fsyntax-only -verify %s
>>>> +extern void f1(int *);
>>>> +extern void f2(char *);
>>>> +
>>>> +struct Ok {
>>>> +  char c;
>>>> +  int x;
>>>> +};
>>>> +
>>>> +struct __attribute__((packed)) Arguable {
>>>> +  char c0;
>>>> +  int x;
>>>> +  char c1;
>>>> +};
>>>> +
>>>> +union __attribute__((packed)) UnionArguable {
>>>> +  char c;
>>>> +  int x;
>>>> +};
>>>> +
>>>> +typedef struct Arguable ArguableT;
>>>> +
>>>> +struct Arguable *get_arguable();
>>>> +
>>>> +void to_void(void *);
>>>> +
>>>> +void g0(void) {
>>>> +  {
>>>> +    struct Ok ok;
>>>> +    f1(&ok.x); // no-warning
>>>> +    f2(&ok.c); // no-warning
>>>> +  }
>>>> +  {
>>>> +    struct Arguable arguable;
>>>> +    f2(&arguable.c0); // no-warning
>>>> +    f1(&arguable.x);  // expected-warning {{packed member 'x' of class
>>>> or structure 'Arguable'}}
>>>> +    f2(&arguable.c1); // no-warning
>>>> +
>>>> +    f1((int *)(void *)&arguable.x); // no-warning
>>>> +    to_void(&arguable.x);           // no-warning
>>>> +    void *p = &arguable.x;          // no-warning;
>>>> +    to_void(p);
>>>> +  }
>>>> +  {
>>>> +    union UnionArguable arguable;
>>>> +    f2(&arguable.c); // no-warning
>>>> +    f1(&arguable.x); // expected-warning {{packed member 'x' of class
>>>> or structure 'UnionArguable'}}
>>>> +
>>>> +    f1((int *)(void *)&arguable.x); // no-warning
>>>> +    to_void(&arguable.x);           // no-warning
>>>> +  }
>>>> +  {
>>>> +    ArguableT arguable;
>>>> +    f2(&arguable.c0); // no-warning
>>>> +    f1(&arguable.x);  // expected-warning {{packed member 'x' of class
>>>> or structure 'Arguable'}}
>>>> +    f2(&arguable.c1); // no-warning
>>>> +
>>>> +    f1((int *)(void *)&arguable.x); // no-warning
>>>> +    to_void(&arguable.x);           // no-warning
>>>> +  }
>>>> +  {
>>>> +    struct Arguable *arguable = get_arguable();
>>>> +    f2(&arguable->c0); // no-warning
>>>> +    f1(&arguable->x);  // expected-warning {{packed member 'x' of
>>>> class or structure 'Arguable'}}
>>>> +    f2(&arguable->c1); // no-warning
>>>> +
>>>> +    f1((int *)(void *)&arguable->x); // no-warning
>>>> +    to_void(&arguable->c1);          // no-warning
>>>> +  }
>>>> +  {
>>>> +    ArguableT *arguable = get_arguable();
>>>> +    f2(&(arguable->c0)); // no-warning
>>>> +    f1(&(arguable->x));  // expected-warning {{packed member 'x' of
>>>> class or structure 'Arguable'}}
>>>> +    f2(&(arguable->c1)); // no-warning
>>>> +
>>>> +    f1((int *)(void *)&(arguable->x)); // no-warning
>>>> +    to_void(&(arguable->c1));          // no-warning
>>>> +  }
>>>> +}
>>>> +
>>>> +struct S1 {
>>>> +  char c;
>>>> +  int i __attribute__((packed));
>>>> +};
>>>> +
>>>> +int *g1(struct S1 *s1) {
>>>> +  return &s1->i; // expected-warning {{packed member 'i' of class or
>>>> structure 'S1'}}
>>>> +}
>>>> +
>>>> +struct S2_i {
>>>> +  int i;
>>>> +};
>>>> +struct __attribute__((packed)) S2 {
>>>> +  char c;
>>>> +  struct S2_i inner;
>>>> +};
>>>> +
>>>> +int *g2(struct S2 *s2) {
>>>> +  return &s2->inner.i; // expected-warning {{packed member 'inner' of
>>>> class or structure 'S2'}}
>>>> +}
>>>> +
>>>> +struct S2_a {
>>>> +  char c;
>>>> +  struct S2_i inner __attribute__((packed));
>>>> +};
>>>> +
>>>> +int *g2_a(struct S2_a *s2_a) {
>>>> +  return &s2_a->inner.i; // expected-warning {{packed member 'inner'
>>>> of class or structure 'S2_a'}}
>>>> +}
>>>> +
>>>> +struct __attribute__((packed)) S3 {
>>>> +  char c;
>>>> +  struct {
>>>> +    int i;
>>>> +  } inner;
>>>> +};
>>>> +
>>>> +int *g3(struct S3 *s3) {
>>>> +  return &s3->inner.i; // expected-warning {{packed member 'inner' of
>>>> class or structure 'S3'}}
>>>> +}
>>>> +
>>>> +struct S4 {
>>>> +  char c;
>>>> +  struct __attribute__((packed)) {
>>>> +    int i;
>>>> +  } inner;
>>>> +};
>>>> +
>>>> +int *g4(struct S4 *s4) {
>>>> +  return &s4->inner.i; // expected-warning {{packed member 'i' of
>>>> class or structure 'S4::(anonymous)'}}
>>>> +}
>>>> +
>>>> +struct S5 {
>>>> +  char c;
>>>> +  struct {
>>>> +    char c1;
>>>> +    int i __attribute__((packed));
>>>> +  } inner;
>>>> +};
>>>> +
>>>> +int *g5(struct S5 *s5) {
>>>> +  return &s5->inner.i; // expected-warning {{packed member 'i' of
>>>> class or structure 'S5::(anonymous)'}}
>>>> +}
>>>> +
>>>> +struct __attribute__((packed, aligned(2))) AlignedTo2 {
>>>> +  int x;
>>>> +};
>>>> +
>>>> +char *g6(struct AlignedTo2 *s) {
>>>> +  return (char *)&s->x; // no-warning
>>>> +}
>>>> +
>>>> +struct __attribute__((packed, aligned(2))) AlignedTo2Bis {
>>>> +  int x;
>>>> +};
>>>> +
>>>> +struct AlignedTo2Bis* g7(struct AlignedTo2 *s)
>>>> +{
>>>> +    return (struct AlignedTo2Bis*)&s->x; // no-warning
>>>> +}
>>>>
>>>> Added: cfe/trunk/test/SemaCXX/address-packed-member-memops.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/address-packed-member-memops.cpp?rev=275417&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/address-packed-member-memops.cpp (added)
>>>> +++ cfe/trunk/test/SemaCXX/address-packed-member-memops.cpp Thu Jul 14
>>>> 09:10:43 2016
>>>> @@ -0,0 +1,28 @@
>>>> +// RUN: %clang_cc1 -fsyntax-only -verify %s
>>>> +// expected-no-diagnostics
>>>> +
>>>> +struct B {
>>>> +  int x, y, z, w;
>>>> +} b;
>>>> +
>>>> +struct __attribute__((packed)) A {
>>>> +  struct B b;
>>>> +} a;
>>>> +
>>>> +typedef __typeof__(sizeof(int)) size_t;
>>>> +
>>>> +extern "C" {
>>>> +void *memcpy(void *dest, const void *src, size_t n);
>>>> +int memcmp(const void *s1, const void *s2, size_t n);
>>>> +void *memmove(void *dest, const void *src, size_t n);
>>>> +void *memset(void *s, int c, size_t n);
>>>> +}
>>>> +
>>>> +int x;
>>>> +
>>>> +void foo() {
>>>> +  memcpy(&a.b, &b, sizeof(b));
>>>> +  memmove(&a.b, &b, sizeof(b));
>>>> +  memset(&a.b, 0, sizeof(b));
>>>> +  x = memcmp(&a.b, &b, sizeof(b));
>>>> +}
>>>>
>>>> Added: cfe/trunk/test/SemaCXX/address-packed.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/address-packed.cpp?rev=275417&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/address-packed.cpp (added)
>>>> +++ cfe/trunk/test/SemaCXX/address-packed.cpp Thu Jul 14 09:10:43 2016
>>>> @@ -0,0 +1,118 @@
>>>> +// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
>>>> +extern void f1(int *);
>>>> +extern void f2(char *);
>>>> +
>>>> +struct __attribute__((packed)) Arguable {
>>>> +  int x;
>>>> +  char c;
>>>> +  static void foo();
>>>> +};
>>>> +
>>>> +extern void f3(void());
>>>> +
>>>> +namespace Foo {
>>>> +struct __attribute__((packed)) Arguable {
>>>> +  char c;
>>>> +  int x;
>>>> +  static void foo();
>>>> +};
>>>> +}
>>>> +
>>>> +struct Arguable *get_arguable();
>>>> +
>>>> +void f4(int &);
>>>> +
>>>> +void to_void(void *);
>>>> +
>>>> +template <typename... T>
>>>> +void sink(T...);
>>>> +
>>>> +void g0() {
>>>> +  {
>>>> +    Foo::Arguable arguable;
>>>> +    f1(&arguable.x);   // expected-warning {{packed member 'x' of
>>>> class or structure 'Foo::Arguable'}}
>>>> +    f2(&arguable.c);   // no-warning
>>>> +    f3(&arguable.foo); // no-warning
>>>> +
>>>> +    int &w = arguable.x; // expected-error {{binding reference to
>>>> packed member 'x' of class or structure 'Foo::Arguable'}}
>>>> +    sink(w);
>>>> +    f4(arguable.x); // expected-error {{binding reference to packed
>>>> member 'x' of class or structure 'Foo::Arguable'}}
>>>> +
>>>> +    to_void(&arguable.x);                             // no-warning
>>>> +    void *p1 = &arguable.x;                           // no-warning
>>>> +    void *p2 = static_cast<void *>(&arguable.x);      // no-warning
>>>> +    void *p3 = reinterpret_cast<void *>(&arguable.x); // no-warning
>>>> +    void *p4 = (void *)&arguable.x;                   // no-warning
>>>> +    sink(p1, p2, p3, p4);
>>>> +  }
>>>> +  {
>>>> +    Arguable arguable1;
>>>> +    Arguable &arguable(arguable1);
>>>> +    f1(&arguable.x);   // expected-warning {{packed member 'x' of
>>>> class or structure 'Arguable'}}
>>>> +    f2(&arguable.c);   // no-warning
>>>> +    f3(&arguable.foo); // no-warning
>>>> +  }
>>>> +  {
>>>> +    Arguable *arguable1;
>>>> +    Arguable *&arguable(arguable1);
>>>> +    f1(&arguable->x);   // expected-warning {{packed member 'x' of
>>>> class or structure 'Arguable'}}
>>>> +    f2(&arguable->c);   // no-warning
>>>> +    f3(&arguable->foo); // no-warning
>>>> +  }
>>>> +}
>>>> +
>>>> +struct __attribute__((packed)) A {
>>>> +  int x;
>>>> +  char c;
>>>> +
>>>> +  int *f0() {
>>>> +    return &this->x; // expected-warning {{packed member 'x' of class
>>>> or structure 'A'}}
>>>> +  }
>>>> +
>>>> +  int *g0() {
>>>> +    return &x; // expected-warning {{packed member 'x' of class or
>>>> structure 'A'}}
>>>> +  }
>>>> +
>>>> +  char *h0() {
>>>> +    return &c; // no-warning
>>>> +  }
>>>> +};
>>>> +
>>>> +struct B : A {
>>>> +  int *f1() {
>>>> +    return &this->x; // expected-warning {{packed member 'x' of class
>>>> or structure 'A'}}
>>>> +  }
>>>> +
>>>> +  int *g1() {
>>>> +    return &x; // expected-warning {{packed member 'x' of class or
>>>> structure 'A'}}
>>>> +  }
>>>> +
>>>> +  char *h1() {
>>>> +    return &c; // no-warning
>>>> +  }
>>>> +};
>>>> +
>>>> +template <typename Ty>
>>>> +class __attribute__((packed)) S {
>>>> +  Ty X;
>>>> +
>>>> +public:
>>>> +  const Ty *get() const {
>>>> +    return &X; // expected-warning {{packed member 'X' of class or
>>>> structure 'S<int>'}}
>>>> +               // expected-warning at -1 {{packed member 'X' of class or
>>>> structure 'S<float>'}}
>>>> +  }
>>>> +};
>>>> +
>>>> +template <typename Ty>
>>>> +void h(Ty *);
>>>> +
>>>> +void g1() {
>>>> +  S<int> s1;
>>>> +  s1.get(); // expected-note {{in instantiation of member function
>>>> 'S<int>::get'}}
>>>> +
>>>> +  S<char> s2;
>>>> +  s2.get();
>>>> +
>>>> +  S<float> s3;
>>>> +  s3.get(); // expected-note {{in instantiation of member function
>>>> 'S<float>::get'}}
>>>> +}
>>>>
>>>>
>>>> _______________________________________________
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>>>> cfe-commits at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>
>>>
>>>
>>> _______________________________________________
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