c++ - GCC 3.x および 4.x の C++ オブジェクトの VTable レイアウトと VTable ポインタの場所は何ですか?

Question

VTable の構造、順序と内容、およびオブジェクト内の vtable ポインタの場所の詳細を探しています。

理想的には、これは単一継承、多重継承、および仮想継承をカバーします。

外部ドキュメントへの参照も歓迎します

GCC 4.0x クラスレイアウトのドキュメントはここにあり、Itanium、およびより広範な GNU、ABI レイアウトドキュメントはここにあります。

score 12 · Accepted Answer

仮想テーブルは通常、関数ポインターの配列として扱われますが、コンパイラーはデータポインター (MI および VI シナリオの場合、または typeinfos へ)、整数 (フィックスアップ用)、またはセンチネル要素 (NULL ポインターなど) を自由に配置できます。同じように。レイアウトは通常、コンパイラ固有 (または複数の C++ コンパイラが ABI を共有する場合は ABI 固有) ですが、コンパイルされるクラスに安定したインターフェイスがある場合は安定しています (そうでない場合は、常にコードを再コンパイルする必要があり、それは面倒です)。 . また、仮想および多重継承を含むコーナーケースを処理するために必要な追加のテーブルもあり、派生クラスの構築中の仮想呼び出しが、それらの状況下で標準で規定されているとおりに動作することを確認します (これらは、以下の出力は用です）。

GCC 4.x の特定のケースに関しては、-fdump-class-hierarchyスイッチは実際に説明されているとおりに機能します (そしていくつか)。以下のサンプルコードを使用して、 Coliruでテストしました。

struct Base
{
    virtual ~Base() {}
    virtual void f() = 0;
};

struct OtherBase
{
    virtual ~OtherBase() {}
    virtual void g() {}
};

struct Derived: public Base
{
    virtual ~Derived() {}
    virtual void f() {}
};

struct MultiplyDerived: public Base, public OtherBase
{
    virtual ~MultiplyDerived() {}
    virtual void f() {}
    virtual void g() {}
};

struct OtherDerived: public Base
{
    virtual ~OtherDerived() {}
    virtual void f() {}
};

struct DiamondDerived: public Derived, public OtherDerived
{
    virtual ~DiamondDerived() {}
    virtual void f() {}
};

struct VirtuallyDerived: virtual public Base
{
    virtual ~VirtuallyDerived() {}
    virtual void f() {}
};

struct OtherVirtuallyDerived: virtual public Base
{
    virtual ~OtherVirtuallyDerived() {}
    virtual void f() {}
};

struct VirtuallyDiamondDerived: public VirtuallyDerived, public OtherVirtuallyDerived
{
    virtual ~VirtuallyDiamondDerived() {}
    virtual void f() {}
};

struct DoublyVirtuallyDiamondDerived: virtual public VirtuallyDerived, virtual public OtherVirtuallyDerived
{
    virtual ~DoublyVirtuallyDiamondDerived() {}
    virtual void f() {}
};

struct MixedVirtuallyDerived: virtual public Base, public OtherBase
{
    virtual ~MixedVirtuallyDerived() {}
};

struct MixedVirtuallyDiamondDerived: public VirtuallyDerived, public MixedVirtuallyDerived
{
    virtual ~MixedVirtuallyDiamondDerived() {}
    virtual void f() {}
    virtual void g() {}
};

struct VirtuallyMultiplyDerived: virtual public Base, virtual public OtherBase
{
    virtual ~VirtuallyMultiplyDerived() {}
};

struct OtherVirtuallyMultiplyDerived: virtual public Base, virtual public OtherBase
{
    virtual ~OtherVirtuallyMultiplyDerived() {}
};

struct MultiplyVirtuallyDiamondDerived: public VirtuallyMultiplyDerived, public OtherVirtuallyMultiplyDerived
{
    virtual ~MultiplyVirtuallyDiamondDerived() {}
    virtual void f() {}
    virtual void g() {}
};

および G++ から受け取ったもの (マングルされた名前のガイド: TI は typeinfo、TV は vtable、Th と Tv はサンクで、多重および/または仮想継承の存在下で正しい仮想呼び出しを行うために使用されます):

Base の Vtable

Base::_ZTV4Base: 5u エントリ

0 (整数 (*)(...))0

8 (整数 (*)(...))(& _ZTI4Base)

16 0u

24 0u

32 (整数 (*)(...))__cxa_pure_virtual


クラスベース

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

ベース (0x0x7fd42c0355a0) 0 ほぼ空

    vptr=((& Base::_ZTV4Base) + 16u)


OtherBase の Vtable

OtherBase::_ZTV9OtherBase: 5u エントリ

0 (整数 (*)(...))0

8 (整数 (*)(...))(& _ZTI9OtherBase)

16 (int (*)(...))OtherBase::~OtherBase

24 (int (*)(...))OtherBase::~OtherBase

32 (整数 (*)(...))OtherBase::g


クラス OtherBase

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

OtherBase (0x0x7fd42c035600) 0 ほぼ空

    vptr=((& その他のベース::_ZTV9その他のベース) + 16u)


派生用の Vtable

派生::_ZTV7派生: 5u エントリ

0 (整数 (*)(...))0

8 (int (*)(...))(& _ZTI7Derived)

16 (int (*)(...))Derived::~Derived

24 (int (*)(...))Derived::~Derived

32 (int (*)(...))Derived::f


派生クラス

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

派生 (0x0x7fd42c02d138) 0 ほとんど空

    vptr=((&派生::_ZTV7派生) + 16u)

  ベース (0x0x7fd42c035660) 0 ほとんど空

      派生用プライマリ (0x0x7fd42c02d138)


MultiplyDerived の Vtable

MultiplyDerived::_ZTV15MultiplyDerived: 11u エントリ

0 (整数 (*)(...))0

8 (int (*)(...))(& _ZTI15MultiplyDerived)

16 (int (*)(...))MultiplyDerived::~MultiplyDerived

24 (int (*)(...))MultiplyDerived::~MultiplyDerived

32 (int (*)(...))MultiplyDerived::f

40 (int (*)(...))MultiplyDerived::g

48 (整数 (*)(...))-8

56 (int (*)(...))(& _ZTI15MultiplyDerived)

64 (int (*)(...))MultiplyDerived::_ZThn8_N15MultiplyDerivedD1Ev

72 (int (*)(...))MultiplyDerived::_ZThn8_N15MultiplyDerivedD0Ev

80 (int (*)(...))MultiplyDerived::_ZThn8_N15MultiplyDerived1gEv


クラス MultiplyDerived

   サイズ=16 整列=8

   base size=16 base align=8

MultiplyDerived (0x0x7fd42c04aaf0) 0

    vptr=((& MultiplyDerived::_ZTV15MultiplyDerived) + 16u)

  ベース (0x0x7fd42c0356c0) 0 ほとんど空

      MultiplyDerived のプライマリ (0x0x7fd42c04aaf0)

  OtherBase (0x0x7fd42c035720) 8 ほとんど空

      vptr=((& MultiplyDerived::_ZTV15MultiplyDerived) + 64u)


OtherDerived の Vtable

OtherDerived::_ZTV12OtherDerived: 5u エントリ

0 (整数 (*)(...))0

8 (int (*)(...))(& _ZTI12OtherDerived)

16 (int (*)(...))OtherDerived::~OtherDerived

24 (int (*)(...))OtherDerived::~OtherDerived

32 (int (*)(...))OtherDerived::f


クラス OtherDerived

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

OtherDerived (0x0x7fd42c02d1a0) 0 ほぼ空

    vptr=((& OtherDerived::_ZTV12OtherDerived) + 16u)

  ベース (0x0x7fd42c035780) 0 ほとんど空

      プライマリ - OtherDerived (0x0x7fd42c02d1a0)


DiamondDerived の Vtable

DiamondDerived::_ZTV14DiamondDerived: 10u エントリ

0 (整数 (*)(...))0

8 (int (*)(...))(& _ZTI14DiamondDerived)

16 (int (*)(...))DiamondDerived::~DiamondDerived

24 (int (*)(...))DiamondDerived::~DiamondDerived

32 (int (*)(...))DiamondDerived::f

40 (整数 (*)(...))-8

48 (int (*)(...))(& _ZTI14DiamondDerived)

56 (int (*)(...))DiamondDerived::_ZThn8_N14DiamondDerivedD1Ev

64 (int (*)(...))DiamondDerived::_ZThn8_N14DiamondDerivedD0Ev

72 (int (*)(...))DiamondDerived::_ZThn8_N14DiamondDerived1fEv


クラス DiamondDerived

   サイズ=16 整列=8

   base size=16 base align=8

DiamondDerived (0x0x7fd42c0625b0) 0

    vptr=((& DiamondDerived::_ZTV14DiamondDerived) + 16u)

  派生 (0x0x7fd42c02d208) 0 ほとんど空

      Primary-DiamondDerived (0x0x7fd42c0625b0) の場合

    ベース (0x0x7fd42c0357e0) 0 ほぼ空

        派生用プライマリ (0x0x7fd42c02d208)

  OtherDerived (0x0x7fd42c02d270) 8 ほとんど空

      vptr=((& DiamondDerived::_ZTV14DiamondDerived) + 56u)

    ベース (0x0x7fd42c035840) 8 ほとんど空

        プライマリ - OtherDerived (0x0x7fd42c02d270)


VirtuallyDerived の Vtable

VirtuallyDerived::_ZTV16VirtuallyDerived: 8u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI16VirtuallyDerived)

40 (int (*)(...))VirtuallyDerived::~VirtuallyDerived

48 (int (*)(...))VirtuallyDerived::~VirtuallyDerived

56 (int (*)(...))VirtuallyDerived::f


VirtuallyDerived の VTT

VirtuallyDerived::_ZTT16VirtuallyDerived: 2u エントリ

0 ((& VirtuallyDerived::_ZTV16VirtuallyDerived) + 40u)

8 ((& VirtuallyDerived::_ZTV16VirtuallyDerived) + 40u)


クラス VirtuallyDerived

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

VirtuallyDerived (0x0x7fd42c02d2d8) 0 ほとんど空

    vptridx=0u vptr=((& VirtuallyDerived::_ZTV16VirtuallyDerived) + 40u)

  ベース (0x0x7fd42c0358a0) 0 ほぼ空の仮想

      primary-for VirtuallyDerived (0x0x7fd42c02d2d8)

      vptridx=8u vbaseoffset=-40


OtherVirtuallyDerived の Vtable

OtherVirtuallyDerived::_ZTV21OtherVirtuallyDerived: 8u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI21OtherVirtuallyDerived)

40 (int (*)(...))OtherVirtuallyDerived::~OtherVirtuallyDerived

48 (int (*)(...))OtherVirtuallyDerived::~OtherVirtuallyDerived

56 (int (*)(...))OtherVirtuallyDerived::f


OtherVirtuallyDerived の VTT

OtherVirtuallyDerived::_ZTT21OtherVirtuallyDerived: 2u エントリ

0 ((& OtherVirtuallyDerived::_ZTV21OtherVirtuallyDerived) + 40u)

8 ((& OtherVirtuallyDerived::_ZTV21OtherVirtuallyDerived) + 40u)


クラス OtherVirtuallyDerived

   サイズ=8 整列=8

   ベースサイズ=8 ベースアライン=8

OtherVirtuallyDerived (0x0x7fd42c02d340) 0 ほぼ空

    vptridx=0u vptr=((& OtherVirtuallyDerived::_ZTV21OtherVirtuallyDerived) + 40u)

  ベース (0x0x7fd42c035900) 0 ほぼ空の仮想

      primary-for OtherVirtuallyDerived (0x0x7fd42c02d340)

      vptridx=8u vbaseoffset=-40


VirtuallyDiamondDerived の Vtable

VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived: 16u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI23VirtuallyDiamondDerived)

40 (int (*)(...))VirtuallyDiamondDerived::~VirtuallyDiamondDerived

48 (int (*)(...))VirtuallyDiamondDerived::~VirtuallyDiamondDerived

56 (int (*)(...))VirtuallyDiamondDerived::f

64 18446744073709551608u

72 18446744073709551608u

80 18446744073709551608u

88 (整数 (*)(...))-8

96 (int (*)(...))(& _ZTI23VirtuallyDiamondDerived)

104 (int (*)(...))VirtuallyDiamondDerived::_ZThn8_N23VirtuallyDiamondDerivedD1Ev

112 (int (*)(...))VirtuallyDiamondDerived::_ZThn8_N23VirtuallyDiamondDerivedD0Ev

120 (int (*)(...))VirtuallyDiamondDerived::_ZThn8_N23VirtuallyDiamondDerived1fEv


VirtuallyDiamondDerived の VirtuallyDerived (0x0x7fd42c02d3a8 インスタンス) の構築 vtable

VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived0_16VirtuallyDerived: 8u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI16VirtuallyDerived)

40 0u

48 0u

56 (int (*)(...))VirtuallyDerived::f


VirtuallyDiamondDerived の OtherVirtuallyDerived (0x0x7fd42c02d410 インスタンス) の構築 vtable

VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived8_21OtherVirtuallyDerived: 15u エントリ

0 18446744073709551608u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI21OtherVirtuallyDerived)

40 0u

48 0u

56 (int (*)(...))OtherVirtuallyDerived::f

64 8u

72 8u

80 (整数 (*)(...))8

88 (int (*)(...))(& _ZTI21OtherVirtuallyDerived)

96 0u

104 0u

112 (int (*)(...))OtherVirtuallyDerived::_ZTv0_n32_N21OtherVirtuallyDerived1fEv


VirtuallyDiamondDerived の VTT

VirtuallyDiamondDerived::_ZTT23VirtuallyDiamondDerived: 7u エントリ

0 ((& VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived) + 40u)

8 ((& VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

16 ((& VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

24 ((& VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived8_21OtherVirtuallyDerived) + 40u)

32 ((& VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived8_21OtherVirtuallyDerived) + 96u)

40 ((& VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived) + 40u)

48 ((& VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived) + 104u)


クラス VirtuallyDiamondDerived

   サイズ=16 整列=8

   base size=16 base align=8

VirtuallyDiamondDerived (0x0x7fd42c07e460) 0

    vptridx=0u vptr=((& VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived) + 40u)

  VirtuallyDerived (0x0x7fd42c02d3a8) 0 ほとんど空

      プライマリ-VirtuallyDiamondDerived (0x0x7fd42c07e460)

      subvttidx=8u

    ベース (0x0x7fd42c035960) 0 ほぼ空の仮想

        primary-for VirtuallyDerived (0x0x7fd42c02d3a8)

        vptridx=40u vbaseoffset=-40

  OtherVirtuallyDerived (0x0x7fd42c02d410) 8 ほとんど空

      失われたプライマリ

      subvttidx=24u vptridx=48u vptr=((& VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived) + 104u)

    ベース (0x0x7fd42c035960) 代替パス


DoublelyVirtuallyDiamondDerived の Vtable

DoublyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived: 18u エントリ

0 8u

8 0u

16 0u

24 0u

32 0u

40 (整数 (*)(...))0

48 (int (*)(...))(& _ZTI29DoublyVirtuallyDiamondDerived)

56 (int (*)(...))DoublyVirtuallyDiamondDerived::~DoublyVirtuallyDiamondDerived

64 (int (*)(...))DoublyVirtuallyDiamondDerived::~DoublyVirtuallyDiamondDerived

72 (int (*)(...))DoublyVirtuallyDiamondDerived::f

80 18446744073709551608u

88 18446744073709551608u

96 18446744073709551608u

104 (整数 (*)(...))-8

112 (int (*)(...))(& _ZTI29DoublyVirtuallyDiamondDerived)

120 (int (*)(...))DoublyVirtuallyDiamondDerived::_ZTv0_n24_N29DoublyVirtuallyDiamondDerivedD1Ev

128 (int (*)(...))DoublyVirtuallyDiamondDerived::_ZTv0_n24_N29DoublyVirtuallyDiamondDerivedD0Ev

136 (int (*)(...))DoublyVirtuallyDiamondDerived::_ZTv0_n32_N29DoublyVirtuallyDiamondDerived1fEv


DoublelyVirtuallyDiamondDerived の VirtuallyDerived の構築 vtable

DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived0_16VirtuallyDerived: 8u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI16VirtuallyDerived)

40 0u

48 0u

56 (int (*)(...))VirtuallyDerived::f


DoublyVirtuallyDiamondDerived の OtherVirtuallyDerived の構築 vtable

DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived8_21OtherVirtuallyDerived: 15u エントリ

0 18446744073709551608u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI21OtherVirtuallyDerived)

40 0u

48 0u

56 (int (*)(...))OtherVirtuallyDerived::f

64 8u

72 8u

80 (整数 (*)(...))8

88 (int (*)(...))(& _ZTI21OtherVirtuallyDerived)

96 0u

104 0u

112 (int (*)(...))OtherVirtuallyDerived::_ZTv0_n32_N21OtherVirtuallyDerived1fEv


DoublelyVirtuallyDiamondDerived の VTT

DoublyVirtuallyDiamondDerived::_ZTT29DoublyVirtuallyDiamondDerived: 8u エントリ

0 ((& DoublyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 56u)

8 ((& DoublelyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 56u)

16 ((& DoublelyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 56u)

24 ((& DoublelyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 120u)

32 ((& DoublelyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

40 ((& DoublelyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

48 ((& DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived8_21OtherVirtuallyDerived) + 40u)

56 ((& DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived8_21OtherVirtuallyDerived) + 96u)


クラス DoublelyVirtuallyDiamondDerived

   サイズ=16 整列=8

   ベースサイズ=8 ベースアライン=8

DoublyVirtuallyDiamondDerived (0x0x7fd42c07ea10) 0 ほぼ空

    vptridx=0u vptr=((& DoublyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 56u)

  VirtuallyDerived (0x0x7fd42c02d478) 0 ほぼ空の仮想

      primary-for DoublelyVirtuallyDiamondDerived (0x0x7fd42c07ea10)

      subvttidx=32u vptridx=8u vbaseoffset=-48

    ベース (0x0x7fd42c035a80) 0 ほぼ空の仮想

        primary-for VirtuallyDerived (0x0x7fd42c02d478)

        vptridx=16u vbaseoffset=-40

  OtherVirtuallyDerived (0x0x7fd42c02d4e0) 8 ほぼ空の仮想

      失われたプライマリ

      subvttidx=48u vptridx=24u vbaseoffset=-56 vptr=((& DoublyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived) + 120u)

    ベース (0x0x7fd42c035a80) 代替パス


MixedVirtuallyDerived の Vtable

MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived: 13u エントリ

0 8u

8 (整数 (*)(...))0

16 (int (*)(...))(& _ZTI21MixedVirtuallyDerived)

24 0u

32 0u

40 (整数 (*)(...))OtherBase::g

48 0u

56 18446744073709551608u

64 (整数 (*)(...))-8

72 (int (*)(...))(& _ZTI21MixedVirtuallyDerived)

80 0u

88 0u

96 (整数 (*)(...))__cxa_pure_virtual


MixedVirtuallyDerived の VTT

MixedVirtuallyDerived::_ZTT21MixedVirtuallyDerived: 2u エントリ

0 ((& MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived) + 24u)

8 ((& MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived) + 80u)


クラス MixedVirtuallyDerived

   サイズ=16 整列=8

   ベースサイズ=8 ベースアライン=8

MixedVirtuallyDerived (0x0x7fd42c07eee0) 0 ほぼ空

    vptridx=0u vptr=((& MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived) + 24u)

  ベース (0x0x7fd42c035c60) 8 ほぼ空の仮想

      vptridx=8u vbaseoffset=-24 vptr=((& MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived) + 80u)

  OtherBase (0x0x7fd42c035cc0) 0 ほぼ空

      プライマリ-MixedVirtuallyDerived 用 (0x0x7fd42c07eee0)


MixedVirtuallyDiamondDerived の Vtable

MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived: 15u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI28MixedVirtuallyDiamondDerived)

40 (int (*)(...))MixedVirtuallyDiamondDerived::~MixedVirtuallyDiamondDerived

48 (int (*)(...))MixedVirtuallyDiamondDerived::~MixedVirtuallyDiamondDerived

56 (int (*)(...))MixedVirtuallyDiamondDerived::f

64 (int (*)(...))MixedVirtuallyDiamondDerived::g

72 18446744073709551608u

80 (整数 (*)(...))-8

88 (int (*)(...))(& _ZTI28MixedVirtuallyDiamondDerived)

96 (int (*)(...))MixedVirtuallyDiamondDerived::_ZThn8_N28MixedVirtuallyDiamondDerivedD1Ev

104 (int (*)(...))MixedVirtuallyDiamondDerived::_ZThn8_N28MixedVirtuallyDiamondDerivedD0Ev

112 (int (*)(...))MixedVirtuallyDiamondDerived::_ZThn8_N28MixedVirtuallyDiamondDerived1gEv


MixedVirtuallyDiamondDerived の VirtuallyDerived (0x0x7fd42c02d750 インスタンス) の構築 vtable

MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived0_16VirtuallyDerived: 8u エントリ

0 0u

8 0u

16 0u

24 (整数 (*)(...))0

32 (int (*)(...))(& _ZTI16VirtuallyDerived)

40 0u

48 0u

56 (int (*)(...))VirtuallyDerived::f


MixedVirtuallyDiamondDerived の MixedVirtuallyDerived (0x0x7fd42c0b5380 インスタンス) の構築 vtable

MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived8_21MixedVirtuallyDerived: 13u エントリ

0 18446744073709551608u

8 (整数 (*)(...))0

16 (int (*)(...))(& _ZTI21MixedVirtuallyDerived)

24 0u

32 0u

40 (整数 (*)(...))OtherBase::g

48 0u

56 8u

64 (整数 (*)(...))8

72 (int (*)(...))(& _ZTI21MixedVirtuallyDerived)

80 0u

88 0u

96 (整数 (*)(...))__cxa_pure_virtual


MixedVirtuallyDiamondDerived の VTT

MixedVirtuallyDiamondDerived::_ZTT28MixedVirtuallyDiamondDerived: 7u エントリ

0 ((& MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived) + 40u)

8 ((& MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

16 ((& MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived0_16VirtuallyDerived) + 40u)

24 ((& MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived8_21MixedVirtuallyDerived) + 24u)

32 ((& MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived8_21MixedVirtuallyDerived) + 80u)

40 ((& MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived) + 40u)

48 ((& MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived) + 96u)


クラス MixedVirtuallyDiamondDerived

   サイズ=16 整列=8

   base size=16 base align=8

MixedVirtuallyDiamondDerived (0x0x7fd42c0b5310) 0

    vptridx=0u vptr=((& MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived) + 40u)

  VirtuallyDerived (0x0x7fd42c02d750) 0 ほとんど空

      プライマリ-MixedVirtuallyDiamondDerived 用 (0x0x7fd42c0b5310)

      subvttidx=8u

    ベース (0x0x7fd42c035d20) 0 ほぼ空の仮想

        primary-for VirtuallyDerived (0x0x7fd42c02d750)

        vptridx=40u vbaseoffset=-40

  MixedVirtuallyDerived (0x0x7fd42c0b5380) 8 ほとんど空

      subvttidx=24u vptridx=48u vptr=((& MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived) + 96u)

    ベース (0x0x7fd42c035d20) 代替パス

    OtherBase (0x0x7fd42c035d80) 8 ほとんど空

        プライマリ-MixedVirtuallyDerived 用 (0x0x7fd42c0b5380)


VirtuallyMultiplyDerived の Vtable

VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived: 16u エントリ

0 8u

8 0u

16 0u

24 0u

32 (整数 (*)(...))0

40 (int (*)(...))(& _ZTI24VirtuallyMultiplyDerived)

48 0u

56 0u

64 (整数 (*)(...))__cxa_pure_virtual

72 0u

80 18446744073709551608u

88 (整数 (*)(...))-8

96 (int (*)(...))(& _ZTI24VirtuallyMultiplyDerived)

104 0u

112 0u

120 (整数 (*)(...))OtherBase::g


VirtuallyMultiplyDerived の VTT

VirtuallyMultiplyDerived::_ZTT24VirtuallyMultiplyDerived: 3u エントリ

0 ((& VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived) + 48u)

8 ((& VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived) + 48u)

16 ((& VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived) + 104u)


クラス VirtuallyMultiplyDerived

   サイズ=16 整列=8

   ベースサイズ=8 ベースアライン=8

VirtuallyMultiplyDerived (0x0x7fd42c0b59a0) 0 ほぼ空

    vptridx=0u vptr=((& VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived) + 48u)

  ベース (0x0x7fd42c035e40) 0 ほぼ空の仮想

      プライマリ - VirtuallyMultiplyDerived 用 (0x0x7fd42c0b59a0)

      vptridx=8u vbaseoffset=-40

  OtherBase (0x0x7fd42c035ea0) 8 ほぼ空の仮想

      vptridx=16u vbaseoffset=-48 vptr=((& VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived) + 104u)


OtherVirtuallyMultiplyDerived の Vtable

OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived: 16u エントリ

0 8u

8 0u

16 0u

24 0u

32 (整数 (*)(...))0

40 (int (*)(...))(& _ZTI29OtherVirtuallyMultiplyDerived)

48 0u

56 0u

64 (整数 (*)(...))__cxa_pure_virtual

72 0u

80 18446744073709551608u

88 (整数 (*)(...))-8

96 (int (*)(...))(& _ZTI29OtherVirtuallyMultiplyDerived)

104 0u

112 0u

120 (整数 (*)(...))OtherBase::g


OtherVirtuallyMultiplyDerived の VTT

OtherVirtuallyMultiplyDerived::_ZTT29OtherVirtuallyMultiplyDerived: 3u エントリ

0 ((& OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived) + 48u)

8 ((& OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived) + 48u)

16 ((& OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived) + 104u)


クラス OtherVirtuallyMultiplyDerived

   サイズ=16 整列=8

   ベースサイズ=8 ベースアライン=8

OtherVirtuallyMultiplyDerived (0x0x7fd42c0b5d90) 0 ほぼ空

    vptridx=0u vptr=((& OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived) + 48u)

  ベース (0x0x7fd42c035f00) 0 ほぼ空の仮想

      primary-for OtherVirtuallyMultiplyDerived (0x0x7fd42c0b5d90)

      vptridx=8u vbaseoffset=-40

  OtherBase (0x0x7fd42c035f60) 8 ほぼ空の仮想

      vptridx=16u vbaseoffset=-48 vptr=((& OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived) + 104u)


MultiplyVirtuallyDiamondDerived の Vtable

MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived: 26u エントリ

0 16u

8 0u

16 0u

24 0u

32 (整数 (*)(...))0

40 (int (*)(...))(& _ZTI31MultiplyVirtuallyDiamondDerived)

48 (int (*)(...))MultiplyVirtuallyDiamondDerived::~MultiplyVirtuallyDiamondDerived

56 (int (*)(...))MultiplyVirtuallyDiamondDerived::~MultiplyVirtuallyDiamondDerived

64 (int (*)(...))MultiplyVirtuallyDiamondDerived::f

72 (int (*)(...))MultiplyVirtuallyDiamondDerived::g

80 8u

88 18446744073709551608u

96 18446744073709551608u

104 18446744073709551608u

112 (整数 (*)(...))-8

120 (int (*)(...))(& _ZTI31MultiplyVirtuallyDiamondDerived)

128 (int (*)(...))MultiplyVirtuallyDiamondDerived::_ZThn8_N31MultiplyVirtuallyDiamondDerivedD1Ev

136 (int (*)(...))MultiplyVirtuallyDiamondDerived::_ZThn8_N31MultiplyVirtuallyDiamondDerivedD0Ev

144 0u

152 18446744073709551600u

160 18446744073709551600u

168 (整数 (*)(...))-16

176 (int (*)(...))(& _ZTI31MultiplyVirtuallyDiamondDerived)

184 (int (*)(...))MultiplyVirtuallyDiamondDerived::_ZTv0_n24_N31MultiplyVirtuallyDiamondDerivedD1Ev

192 (int (*)(...))MultiplyVirtuallyDiamondDerived::_ZTv0_n24_N31MultiplyVirtuallyDiamondDerivedD0Ev

200 (int (*)(...))MultiplyVirtuallyDiamondDerived::_ZTv0_n32_N31MultiplyVirtuallyDiamondDerived1gEv


MultiplyVirtuallyDiamondDerived の VirtuallyMultiplyDerived (0x0x7fd42bcdf230 インスタンス) の構築 vtable

MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived0_24VirtuallyMultiplyDerived: 16u エントリ

0 16u

8 0u

16 0u

24 0u

32 (整数 (*)(...))0

40 (int (*)(...))(& _ZTI24VirtuallyMultiplyDerived)

48 0u

56 0u

64 (整数 (*)(...))__cxa_pure_virtual

72 0u

80 18446744073709551600u

88 (整数 (*)(...))-16

96 (int (*)(...))(& _ZTI24VirtuallyMultiplyDerived)

104 0u

112 0u

120 (整数 (*)(...))OtherBase::g


MultiplyVirtuallyDiamondDerived の OtherVirtuallyMultiplyDerived (0x0x7fd42bcdf2a0 インスタンス) の構築 vtable

MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived8_29OtherVirtuallyMultiplyDerived: 23u エントリ

0 8u

8 18446744073709551608u

16 18446744073709551608u

24 0u

32 (整数 (*)(...))0

40 (int (*)(...))(& _ZTI29OtherVirtuallyMultiplyDerived)

48 0u

56 0u

64 (整数 (*)(...))__cxa_pure_virtual

72 0u

80 8u

88 (整数 (*)(...))8

96 (int (*)(...))(& _ZTI29OtherVirtuallyMultiplyDerived)

104 0u

112 0u

120 (整数 (*)(...))__cxa_pure_virtual

128 0u

136 18446744073709551608u

144 (整数 (*)(...))-8

152 (int (*)(...))(& _ZTI29OtherVirtuallyMultiplyDerived)

160 0u

168 0u

176 (整数 (*)(...))OtherBase::g


MultiplyVirtuallyDiamondDerived の VTT

MultiplyVirtuallyDiamondDerived::_ZTT31MultiplyVirtuallyDiamondDerived: 10u エントリ

0 ((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 48u)

8 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived0_24VirtuallyMultiplyDerived) + 48u)

16 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived0_24VirtuallyMultiplyDerived) + 48u)

24 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived0_24VirtuallyMultiplyDerived) + 104u)

32 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived8_29OtherVirtuallyMultiplyDerived) + 48u)

40 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived8_29OtherVirtuallyMultiplyDerived) + 104u)

48 ((& MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived8_29OtherVirtuallyMultiplyDerived) + 160u)

56 ((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 48u)

64 ((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 184u)

72 ((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 128u)


クラス MultiplyVirtuallyDiamondDerived

   サイズ=24 整列=8

   base size=16 base align=8

MultiplyVirtuallyDiamondDerived (0x0x7fd42bcdf1c0) 0

    vptridx=0u vptr=((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 48u)

  VirtuallyMultiplyDerived (0x0x7fd42bcdf230) 0 ほぼ空

      プライマリ-MultiplyVirtuallyDiamondDerived (0x0x7fd42bcdf1c0) の場合

      subvttidx=8u

    ベース (0x0x7fd42bce2000) 0 ほぼ空の仮想

        プライマリ - VirtuallyMultiplyDerived 用 (0x0x7fd42bcdf230)

        vptridx=56u vbaseoffset=-40

    OtherBase (0x0x7fd42bce2060) 16 ほぼ空の仮想

        vptridx=64u vbaseoffset=-48 vptr=((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 184u)

  OtherVirtuallyMultiplyDerived (0x0x7fd42bcdf2a0) 8 ほぼ空

      失われたプライマリ

      subvttidx=32u vptridx=72u vptr=((& MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived) + 128u)

    ベース (0x0x7fd42bce2000) 代替パス

    OtherBase (0x0x7fd42bce2060) 代替パス

score -5 · Accepted Answer

私が見たコンパイラの実装のほとんどは、基本オブジェクトを派生オブジェクトに「埋め込む」だけです。オブジェクトへの相対オフセットは、コンパイル時に参照が評価されるときに追加されるだけなので、vtable が保持される場所は無関係になります。

多重継承と仮想継承はより複雑で、アクセス対象に応じて異なるオフセットが必要になる場合があります。

Code Project: The Impossively Fast C++ Delegatesに関するこの記事を読むことを強くお勧めします。

さまざまなコンパイラが継承のさまざまな側面をどのように処理するかについて、全体像を見事に示しています。さまざまなコンパイラの低レベルの動作に興味がある場合は、ぜひお読みください。

編集：そこに間違った記事をリンクしました。訂正しました。

c++ - GCC 3.x および 4.x の C++ オブジェクトの VTable レイアウトと VTable ポインタの場所は何ですか?

2 に答える 2

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