Understanding the tagVARIANT struct

Question

The COM VARIANT type is defined using the tagVARIANT structure like this:

typedef struct tagVARIANT {
  union {
    struct {
      VARTYPE vt;
      WORD    wReserved1;
      WORD    wReserved2;
      WORD    wReserved3;
      union {
        LONGLONG     llVal;
        LONG         lVal;
        BYTE         bVal;
        SHORT        iVal;
        FLOAT        fltVal;
        DOUBLE       dblVal;
        VARIANT_BOOL boolVal;
        VARIANT_BOOL __OBSOLETE__VARIANT_BOOL;
        SCODE        scode;
        CY           cyVal;
        DATE         date;
        BSTR         bstrVal;
        IUnknown     *punkVal;
        IDispatch    *pdispVal;
        SAFEARRAY    *parray;
        BYTE         *pbVal;
        SHORT        *piVal;
        LONG         *plVal;
        LONGLONG     *pllVal;
        FLOAT        *pfltVal;
        DOUBLE       *pdblVal;
        VARIANT_BOOL *pboolVal;
        VARIANT_BOOL *__OBSOLETE__VARIANT_PBOOL;
        SCODE        *pscode;
        CY           *pcyVal;
        DATE         *pdate;
        BSTR         *pbstrVal;
        IUnknown     **ppunkVal;
        IDispatch    **ppdispVal;
        SAFEARRAY    **pparray;
        VARIANT      *pvarVal;
        PVOID        byref;
        CHAR         cVal;
        USHORT       uiVal;
        ULONG        ulVal;
        ULONGLONG    ullVal;
        INT          intVal;
        UINT         uintVal;
        DECIMAL      *pdecVal;
        CHAR         *pcVal;
        USHORT       *puiVal;
        ULONG        *pulVal;
        ULONGLONG    *pullVal;
        INT          *pintVal;
        UINT         *puintVal;
        struct {
          PVOID       pvRecord;
          IRecordInfo *pRecInfo;
        } __VARIANT_NAME_4;
      } __VARIANT_NAME_3;
    } __VARIANT_NAME_2;
    DECIMAL decVal;
  } __VARIANT_NAME_1;
} VARIANT;

I'm just wondering: what do all those __VARIANT_NAME_... labels mean?

I'm trying to construct one of these manually in VBA, and would like to understand what all the members mean

Answer 1

What does __VARIANT_NAME_1 mean in a union struct?

typedef struct tagVARIANT {
  union {
    ....
  } __VARIANT_NAME_1;
} VARIANT;

It is the name of a variable of that unnamed union type. In this context, the variable is a member of tagVARIANT.

P.S. __VARIANT_NAME_1 and several other names in that definition are names reserved to the language implementation.