Object是什么

class Object
{
    PTR_MethodTable m_pMethTab;
}

typedef DPTR(class MethodTable) PTR_MethodTable;

PTR_ObjHeader GetHeader()
{
    LIMITED_METHOD_DAC_CONTRACT;
    return dac_cast<PTR_ObjHeader>(this) - 1;
}

PTR_BYTE GetData(void)
{
    LIMITED_METHOD_CONTRACT;
    SUPPORTS_DAC;
    return dac_cast<PTR_BYTE>(this) + sizeof(Object);
}

class ObjHeader
{
// !!! Notice: m_SyncBlockValue *MUST* be the last field in ObjHeader.
#ifdef _WIN64
    DWORD    m_alignpad;
#endif // _WIN64
    
    Volatile<DWORD> m_SyncBlockValue;      // the Index and the Bits
}

class MethodTable
{
    // Low WORD is component size for array and string types (HasComponentSize() returns true).
    // Used for flags otherwise.
    DWORD m_dwFlags;
    
    // Base size of instance of this class when allocated on the heap
    DWORD m_BaseSize;
    
    WORD m_wFlags2;
    
    // Class token if it fits into 16-bits. If this is (WORD)-1, the class token is stored in the TokenOverflow optional member.
    WORD m_wToken;
    
    // <NICE> In the normal cases we shouldn‘t need a full word for each of these </NICE>
    WORD m_wNumVirtuals;
    WORD m_wNumInterfaces;
    
#ifdef _DEBUG
    LPCUTF8 debug_m_szClassName;
#endif //_DEBUG
    
    // Parent PTR_MethodTable if enum_flag_HasIndirectParent is not set. Pointer to indirection cell
    // if enum_flag_enum_flag_HasIndirectParent is set. The indirection is offset by offsetof(MethodTable, m_pParentMethodTable).
    // It allows casting helpers to go through parent chain natually. Casting helper do not need need the explicit check
    // for enum_flag_HasIndirectParentMethodTable.
    TADDR m_pParentMethodTable;
    
    PTR_Module m_pLoaderModule;    // LoaderModule. It is equal to the ZapModule in ngened images
    
    PTR_MethodTableWriteableData m_pWriteableData;
    
    union {
        EEClass *   m_pEEClass;
        TADDR       m_pCanonMT;
    };
    
    // m_pPerInstInfo and m_pInterfaceMap have to be at fixed offsets because of performance sensitive 
    // JITed code and JIT helpers. However, they are frequently not present. The space is used by other
    // multipurpose slots on first come first served basis if the fixed ones are not present. The other 
    // multipurpose are DispatchMapSlot, NonVirtualSlots, ModuleOverride (see enum_flag_MultipurposeSlotsMask).
    // The multipurpose slots that do not fit are stored after vtable slots.
    union
    {
        PTR_Dictionary *    m_pPerInstInfo;
        TADDR               m_ElementTypeHnd;
        TADDR               m_pMultipurposeSlot1;
    };
    
    union
    {
        InterfaceInfo_t *   m_pInterfaceMap;
        TADDR               m_pMultipurposeSlot2;
    };
    
    // 接下来还有一堆OPTIONAL_MEMBERS，这里省去介绍
}

#define PyObject_HEAD PyObject ob_base; // 每个子类都需要把这个放在最开头

typedef struct _object {
#ifdef Py_TRACE_REFS
    struct _object *_ob_next; // Heap中的前一个对象
    struct _object *_ob_prev; // Heap中的后一个对象
#endif
    Py_ssize_t ob_refcnt; // 引用计数
    struct _typeobject *ob_type; // 指向类型信息
} PyObject;