GCC 3.x和4.x中的C++对象中的VTable布局和VTable指针位置是什么？

agxfikkp  于 2023-05-30  发布在  其他
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我正在寻找VTable结构、顺序和内容的详细信息，以及对象中VTable指针的位置。
理想情况下，这将涵盖单一继承、多重继承和虚拟继承。
也欢迎参考外部文件
GCC 4.0x类布局的文档在这里，Itanium和更广泛的GNU，ABI布局文档在这里。

c++

2条答案

按热度按时间
fkvaft9z

fkvaft9z1#

虚表通常被视为函数指针的数组，尽管编译器可以自由地将数据指针（在MI和VI场景中，或typeinfo），整数（用于修复）或哨兵元素（如NULL指针）放入其中。布局通常是特定于编译器的（或特定于ABI的，其中多个C++编译器共享一个ABI），但如果正在编译的类具有稳定的接口，则是稳定的（否则您必须始终重新编译代码，这是一个阻力）。还有一些额外的表需要处理涉及虚继承和多重继承的极端情况，并确保派生类构造期间的虚调用在这些情况下按照标准的规定进行（这些就是下面输出中的VTT和构造表的用途）。
关于GCC 4.x的具体情况：-fdump-class-hierarchy交换机实际上如所描述的那样（然后是一些）起作用。我使用下面的示例代码在Coliru上测试了它：

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() {}
};

并从G++接收（mangled name guide：TI是typeinfos，TV是vtable，Th和Tv是用于在存在多重和/或虚拟继承的情况下进行正确虚拟调用的thunk）：

Vtable for Base

Base::_ZTV4Base: 5u entries

0     (int (*)(...))0

8     (int (*)(...))(& _ZTI4Base)

16    0u

24    0u

32    (int (*)(...))__cxa_pure_virtual

Class Base

   size=8 align=8

   base size=8 base align=8

Base (0x0x7fd42c0355a0) 0 nearly-empty

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

Vtable for OtherBase

OtherBase::_ZTV9OtherBase: 5u entries

0     (int (*)(...))0

8     (int (*)(...))(& _ZTI9OtherBase)

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

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

32    (int (*)(...))OtherBase::g

Class OtherBase

   size=8 align=8

   base size=8 base align=8

OtherBase (0x0x7fd42c035600) 0 nearly-empty

    vptr=((& OtherBase::_ZTV9OtherBase) + 16u)

Vtable for Derived

Derived::_ZTV7Derived: 5u entries

0     (int (*)(...))0

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

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

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

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

Class Derived

   size=8 align=8

   base size=8 base align=8

Derived (0x0x7fd42c02d138) 0 nearly-empty

    vptr=((& Derived::_ZTV7Derived) + 16u)

  Base (0x0x7fd42c035660) 0 nearly-empty

      primary-for Derived (0x0x7fd42c02d138)

Vtable for MultiplyDerived

MultiplyDerived::_ZTV15MultiplyDerived: 11u entries

0     (int (*)(...))0

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

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

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

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

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

48    (int (*)(...))-8

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

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

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

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

Class MultiplyDerived

   size=16 align=8

   base size=16 base align=8

MultiplyDerived (0x0x7fd42c04aaf0) 0

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

  Base (0x0x7fd42c0356c0) 0 nearly-empty

      primary-for MultiplyDerived (0x0x7fd42c04aaf0)

  OtherBase (0x0x7fd42c035720) 8 nearly-empty

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

Vtable for OtherDerived

OtherDerived::_ZTV12OtherDerived: 5u entries

0     (int (*)(...))0

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

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

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

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

Class OtherDerived

   size=8 align=8

   base size=8 base align=8

OtherDerived (0x0x7fd42c02d1a0) 0 nearly-empty

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

  Base (0x0x7fd42c035780) 0 nearly-empty

      primary-for OtherDerived (0x0x7fd42c02d1a0)

Vtable for DiamondDerived

DiamondDerived::_ZTV14DiamondDerived: 10u entries

0     (int (*)(...))0

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

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

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

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

40    (int (*)(...))-8

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

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

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

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

Class DiamondDerived

   size=16 align=8

   base size=16 base align=8

DiamondDerived (0x0x7fd42c0625b0) 0

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

  Derived (0x0x7fd42c02d208) 0 nearly-empty

      primary-for DiamondDerived (0x0x7fd42c0625b0)

    Base (0x0x7fd42c0357e0) 0 nearly-empty

        primary-for Derived (0x0x7fd42c02d208)

  OtherDerived (0x0x7fd42c02d270) 8 nearly-empty

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

    Base (0x0x7fd42c035840) 8 nearly-empty

        primary-for OtherDerived (0x0x7fd42c02d270)

Vtable for VirtuallyDerived

VirtuallyDerived::_ZTV16VirtuallyDerived: 8u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

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

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

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

VTT for VirtuallyDerived

VirtuallyDerived::_ZTT16VirtuallyDerived: 2u entries

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

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

Class VirtuallyDerived

   size=8 align=8

   base size=8 base align=8

VirtuallyDerived (0x0x7fd42c02d2d8) 0 nearly-empty

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

  Base (0x0x7fd42c0358a0) 0 nearly-empty virtual

      primary-for VirtuallyDerived (0x0x7fd42c02d2d8)

      vptridx=8u vbaseoffset=-40

Vtable for OtherVirtuallyDerived

OtherVirtuallyDerived::_ZTV21OtherVirtuallyDerived: 8u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

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

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

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

VTT for OtherVirtuallyDerived

OtherVirtuallyDerived::_ZTT21OtherVirtuallyDerived: 2u entries

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

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

Class OtherVirtuallyDerived

   size=8 align=8

   base size=8 base align=8

OtherVirtuallyDerived (0x0x7fd42c02d340) 0 nearly-empty

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

  Base (0x0x7fd42c035900) 0 nearly-empty virtual

      primary-for OtherVirtuallyDerived (0x0x7fd42c02d340)

      vptridx=8u vbaseoffset=-40

Vtable for VirtuallyDiamondDerived

VirtuallyDiamondDerived::_ZTV23VirtuallyDiamondDerived: 16u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

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

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

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

64    18446744073709551608u

72    18446744073709551608u

80    18446744073709551608u

88    (int (*)(...))-8

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

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

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

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

Construction vtable for VirtuallyDerived (0x0x7fd42c02d3a8 instance) in VirtuallyDiamondDerived

VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived0_16VirtuallyDerived: 8u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

40    0u

48    0u

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

Construction vtable for OtherVirtuallyDerived (0x0x7fd42c02d410 instance) in VirtuallyDiamondDerived

VirtuallyDiamondDerived::_ZTC23VirtuallyDiamondDerived8_21OtherVirtuallyDerived: 15u entries

0     18446744073709551608u

8     0u

16    0u

24    (int (*)(...))0

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

40    0u

48    0u

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

64    8u

72    8u

80    (int (*)(...))8

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

96    0u

104   0u

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

VTT for VirtuallyDiamondDerived

VirtuallyDiamondDerived::_ZTT23VirtuallyDiamondDerived: 7u entries

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)

Class VirtuallyDiamondDerived

   size=16 align=8

   base size=16 base align=8

VirtuallyDiamondDerived (0x0x7fd42c07e460) 0

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

  VirtuallyDerived (0x0x7fd42c02d3a8) 0 nearly-empty

      primary-for VirtuallyDiamondDerived (0x0x7fd42c07e460)

      subvttidx=8u

    Base (0x0x7fd42c035960) 0 nearly-empty virtual

        primary-for VirtuallyDerived (0x0x7fd42c02d3a8)

        vptridx=40u vbaseoffset=-40

  OtherVirtuallyDerived (0x0x7fd42c02d410) 8 nearly-empty

      lost-primary

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

    Base (0x0x7fd42c035960) alternative-path

Vtable for DoublyVirtuallyDiamondDerived

DoublyVirtuallyDiamondDerived::_ZTV29DoublyVirtuallyDiamondDerived: 18u entries

0     8u

8     0u

16    0u

24    0u

32    0u

40    (int (*)(...))0

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

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

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

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

80    18446744073709551608u

88    18446744073709551608u

96    18446744073709551608u

104   (int (*)(...))-8

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

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

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

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

Construction vtable for VirtuallyDerived in DoublyVirtuallyDiamondDerived

DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived0_16VirtuallyDerived: 8u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

40    0u

48    0u

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

Construction vtable for OtherVirtuallyDerived in DoublyVirtuallyDiamondDerived

DoublyVirtuallyDiamondDerived::_ZTC29DoublyVirtuallyDiamondDerived8_21OtherVirtuallyDerived: 15u entries

0     18446744073709551608u

8     0u

16    0u

24    (int (*)(...))0

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

40    0u

48    0u

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

64    8u

72    8u

80    (int (*)(...))8

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

96    0u

104   0u

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

VTT for DoublyVirtuallyDiamondDerived

DoublyVirtuallyDiamondDerived::_ZTT29DoublyVirtuallyDiamondDerived: 8u entries

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

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

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

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

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

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

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

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

Class DoublyVirtuallyDiamondDerived

   size=16 align=8

   base size=8 base align=8

DoublyVirtuallyDiamondDerived (0x0x7fd42c07ea10) 0 nearly-empty

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

  VirtuallyDerived (0x0x7fd42c02d478) 0 nearly-empty virtual

      primary-for DoublyVirtuallyDiamondDerived (0x0x7fd42c07ea10)

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

    Base (0x0x7fd42c035a80) 0 nearly-empty virtual

        primary-for VirtuallyDerived (0x0x7fd42c02d478)

        vptridx=16u vbaseoffset=-40

  OtherVirtuallyDerived (0x0x7fd42c02d4e0) 8 nearly-empty virtual

      lost-primary

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

    Base (0x0x7fd42c035a80) alternative-path

Vtable for MixedVirtuallyDerived

MixedVirtuallyDerived::_ZTV21MixedVirtuallyDerived: 13u entries

0     8u

8     (int (*)(...))0

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

24    0u

32    0u

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

48    0u

56    18446744073709551608u

64    (int (*)(...))-8

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

80    0u

88    0u

96    (int (*)(...))__cxa_pure_virtual

VTT for MixedVirtuallyDerived

MixedVirtuallyDerived::_ZTT21MixedVirtuallyDerived: 2u entries

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

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

Class MixedVirtuallyDerived

   size=16 align=8

   base size=8 base align=8

MixedVirtuallyDerived (0x0x7fd42c07eee0) 0 nearly-empty

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

  Base (0x0x7fd42c035c60) 8 nearly-empty virtual

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

  OtherBase (0x0x7fd42c035cc0) 0 nearly-empty

      primary-for MixedVirtuallyDerived (0x0x7fd42c07eee0)

Vtable for MixedVirtuallyDiamondDerived

MixedVirtuallyDiamondDerived::_ZTV28MixedVirtuallyDiamondDerived: 15u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

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

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

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

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

72    18446744073709551608u

80    (int (*)(...))-8

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

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

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

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

Construction vtable for VirtuallyDerived (0x0x7fd42c02d750 instance) in MixedVirtuallyDiamondDerived

MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived0_16VirtuallyDerived: 8u entries

0     0u

8     0u

16    0u

24    (int (*)(...))0

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

40    0u

48    0u

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

Construction vtable for MixedVirtuallyDerived (0x0x7fd42c0b5380 instance) in MixedVirtuallyDiamondDerived

MixedVirtuallyDiamondDerived::_ZTC28MixedVirtuallyDiamondDerived8_21MixedVirtuallyDerived: 13u entries

0     18446744073709551608u

8     (int (*)(...))0

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

24    0u

32    0u

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

48    0u

56    8u

64    (int (*)(...))8

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

80    0u

88    0u

96    (int (*)(...))__cxa_pure_virtual

VTT for MixedVirtuallyDiamondDerived

MixedVirtuallyDiamondDerived::_ZTT28MixedVirtuallyDiamondDerived: 7u entries

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)

Class MixedVirtuallyDiamondDerived

   size=16 align=8

   base size=16 base align=8

MixedVirtuallyDiamondDerived (0x0x7fd42c0b5310) 0

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

  VirtuallyDerived (0x0x7fd42c02d750) 0 nearly-empty

      primary-for MixedVirtuallyDiamondDerived (0x0x7fd42c0b5310)

      subvttidx=8u

    Base (0x0x7fd42c035d20) 0 nearly-empty virtual

        primary-for VirtuallyDerived (0x0x7fd42c02d750)

        vptridx=40u vbaseoffset=-40

  MixedVirtuallyDerived (0x0x7fd42c0b5380) 8 nearly-empty

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

    Base (0x0x7fd42c035d20) alternative-path

    OtherBase (0x0x7fd42c035d80) 8 nearly-empty

        primary-for MixedVirtuallyDerived (0x0x7fd42c0b5380)

Vtable for VirtuallyMultiplyDerived

VirtuallyMultiplyDerived::_ZTV24VirtuallyMultiplyDerived: 16u entries

0     8u

8     0u

16    0u

24    0u

32    (int (*)(...))0

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

48    0u

56    0u

64    (int (*)(...))__cxa_pure_virtual

72    0u

80    18446744073709551608u

88    (int (*)(...))-8

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

104   0u

112   0u

120   (int (*)(...))OtherBase::g

VTT for VirtuallyMultiplyDerived

VirtuallyMultiplyDerived::_ZTT24VirtuallyMultiplyDerived: 3u entries

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

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

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

Class VirtuallyMultiplyDerived

   size=16 align=8

   base size=8 base align=8

VirtuallyMultiplyDerived (0x0x7fd42c0b59a0) 0 nearly-empty

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

  Base (0x0x7fd42c035e40) 0 nearly-empty virtual

      primary-for VirtuallyMultiplyDerived (0x0x7fd42c0b59a0)

      vptridx=8u vbaseoffset=-40

  OtherBase (0x0x7fd42c035ea0) 8 nearly-empty virtual

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

Vtable for OtherVirtuallyMultiplyDerived

OtherVirtuallyMultiplyDerived::_ZTV29OtherVirtuallyMultiplyDerived: 16u entries

0     8u

8     0u

16    0u

24    0u

32    (int (*)(...))0

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

48    0u

56    0u

64    (int (*)(...))__cxa_pure_virtual

72    0u

80    18446744073709551608u

88    (int (*)(...))-8

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

104   0u

112   0u

120   (int (*)(...))OtherBase::g

VTT for OtherVirtuallyMultiplyDerived

OtherVirtuallyMultiplyDerived::_ZTT29OtherVirtuallyMultiplyDerived: 3u entries

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

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

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

Class OtherVirtuallyMultiplyDerived

   size=16 align=8

   base size=8 base align=8

OtherVirtuallyMultiplyDerived (0x0x7fd42c0b5d90) 0 nearly-empty

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

  Base (0x0x7fd42c035f00) 0 nearly-empty virtual

      primary-for OtherVirtuallyMultiplyDerived (0x0x7fd42c0b5d90)

      vptridx=8u vbaseoffset=-40

  OtherBase (0x0x7fd42c035f60) 8 nearly-empty virtual

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

Vtable for MultiplyVirtuallyDiamondDerived

MultiplyVirtuallyDiamondDerived::_ZTV31MultiplyVirtuallyDiamondDerived: 26u entries

0     16u

8     0u

16    0u

24    0u

32    (int (*)(...))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   (int (*)(...))-8

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

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

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

144   0u

152   18446744073709551600u

160   18446744073709551600u

168   (int (*)(...))-16

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

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

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

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

Construction vtable for VirtuallyMultiplyDerived (0x0x7fd42bcdf230 instance) in MultiplyVirtuallyDiamondDerived

MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived0_24VirtuallyMultiplyDerived: 16u entries

0     16u

8     0u

16    0u

24    0u

32    (int (*)(...))0

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

48    0u

56    0u

64    (int (*)(...))__cxa_pure_virtual

72    0u

80    18446744073709551600u

88    (int (*)(...))-16

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

104   0u

112   0u

120   (int (*)(...))OtherBase::g

Construction vtable for OtherVirtuallyMultiplyDerived (0x0x7fd42bcdf2a0 instance) in MultiplyVirtuallyDiamondDerived

MultiplyVirtuallyDiamondDerived::_ZTC31MultiplyVirtuallyDiamondDerived8_29OtherVirtuallyMultiplyDerived: 23u entries

0     8u

8     18446744073709551608u

16    18446744073709551608u

24    0u

32    (int (*)(...))0

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

48    0u

56    0u

64    (int (*)(...))__cxa_pure_virtual

72    0u

80    8u

88    (int (*)(...))8

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

104   0u

112   0u

120   (int (*)(...))__cxa_pure_virtual

128   0u

136   18446744073709551608u

144   (int (*)(...))-8

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

160   0u

168   0u

176   (int (*)(...))OtherBase::g

VTT for MultiplyVirtuallyDiamondDerived

MultiplyVirtuallyDiamondDerived::_ZTT31MultiplyVirtuallyDiamondDerived: 10u entries

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)

Class MultiplyVirtuallyDiamondDerived

   size=24 align=8

   base size=16 base align=8

MultiplyVirtuallyDiamondDerived (0x0x7fd42bcdf1c0) 0

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

  VirtuallyMultiplyDerived (0x0x7fd42bcdf230) 0 nearly-empty

      primary-for MultiplyVirtuallyDiamondDerived (0x0x7fd42bcdf1c0)

      subvttidx=8u

    Base (0x0x7fd42bce2000) 0 nearly-empty virtual

        primary-for VirtuallyMultiplyDerived (0x0x7fd42bcdf230)

        vptridx=56u vbaseoffset=-40

    OtherBase (0x0x7fd42bce2060) 16 nearly-empty virtual

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

  OtherVirtuallyMultiplyDerived (0x0x7fd42bcdf2a0) 8 nearly-empty

      lost-primary

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

    Base (0x0x7fd42bce2000) alternative-path

    OtherBase (0x0x7fd42bce2060) alternative-path
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dced5bon

dced5bon2#

我见过的大多数编译器实现只是将基对象“嵌入”到派生对象中。它与保存vtable的位置无关，因为对象的相对偏移量将在编译时计算引用时添加。
多重继承和虚拟继承更复杂，并且根据所访问的内容可能需要不同的偏移量。
我强烈推荐阅读这篇关于Code Project的文章：The Impossibly Fast C++ Delegates
它出色地展示了不同的编译器如何处理继承的各个方面。如果你对不同编译器的底层工作感兴趣，这本书是一本很棒的书。
编辑：我把错误的文章链接在那里。更正。

赞(0）分享  回复(0）举报  2023-05-30
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