VARIANT and VARIANTARG

Use VARIANTARG to describe arguments passed within DISPPARAMS, and VARIANT to specify variant data that cannot be passed by reference. The VARIANT type cannot have the VT_BYREF bit set. VARIANTs can be passed by value, even if VARIANTARGs cannot.

typedef struct FARSTRUCT tagVARIANT VARIANT;
typedef struct FARSTRUCT tagVARIANT VARIANTARG;

typedef struct tagVARIANT  {
    VARTYPE vt;
    unsigned short wReserved1;
    unsigned short wReserved2;
    unsigned short wReserved3;
    union {
        unsigned char        bVal;                        // VT_UI1.
        short                    iVal;                        // VT_I2    .
        long                    lVal;                        // VT_I4    .
        float                    fltVal;                    // VT_R4    .
        double                dblVal;                    // VT_R8    .
        VARIANT_BOOL        boolVal;                        // VT_BOOL.
        SCODE                    scode;                    // VT_ERROR.
        CY                        cyVal;                    // VT_CY    .
        DATE                    date;                        // VT_DATE.
        BSTR                    bstrVal;                    // VT_BSTR.
        IUnknown                FAR* punkVal;            // VT_UNKNOWN.
        IDispatch             FAR* pdispVal;            // VT_DISPATCH.
        SAFEARRAY            FAR* parray;            // VT_ARRAY|*.
        unsigned char        FAR* pbVal;                // VT_BYREF|VT_UI1.
        short                    FAR* piVal;                // VT_BYREF|VT_I2.
        long                    FAR* plVal;                // VT_BYREF|VT_I4.
        float                    FAR* pfltVal;            // VT_BYREF|VT_R4.
        double                FAR* pdblVal;            // VT_BYREF|VT_R8.
        VARIANT_BOOL        FAR* pboolVal;                // VT_BYREF|VT_BOOL.
        SCODE                    FAR* pscode;            // VT_BYREF|VT_ERROR.
        CY                        FAR* pcyVal;            // VT_BYREF|VT_CY.
        DATE                    FAR* pdate;                // VT_BYREF|VT_DATE.
        BSTR                    FAR* pbstrVal;            // VT_BYREF|VT_BSTR.
        IUnknown FAR*        FAR* ppunkVal;            // VT_BYREF|VT_UNKNOWN.
        IDispatch FAR*        FAR* ppdispVal;        // VT_BYREF|VT_DISPATCH.
        SAFEARRAY FAR*        FAR* pparray;            // VT_ARRAY|*.
        VARIANT                FAR* pvarVal;            // VT_BYREF|VT_VARIANT.
        void                    FAR* byref;                // Generic ByRef.
    };
};
 

To simplify extracting values from VARIANTARGs, Automation provides a set of functions for manipulating this type. Use of these functions is strongly recommended to ensure that applications apply consistent coercion rules.

The vt value governs the interpretation of the union as follows: