activex控件返回BSTR* 的方法

STDMETHODIMP CVXNAgent::VXNGetData( BSTR* pbstrOutData)
{
 *pbstrOutData = SysAllocString(_T("0"));
}

SysAllocString的定义

BSTR SysAllocString(
  OLECHAR FAR* sz
);

注意

BSTR bstr = ::SysAllocString(L"My BSTR");

可以

但是

void __stdcall GetString(/*[out]*/ BSTR* pBstrReceiver) { *pBstrReceiver = L"My BSTR"; }不行，因为字符串的长度不对
STDMETHODIMP CVXNAgent::VXNGetData( BSTR* pbstrOutData)
{
  CString csVersionDesc, csDesc;
 csDesc.LoadString(g_hInstance, IDS_VERSION_DESC);
 csVersionDesc.Format(VPN_FORMAT_VERSION_DESC, csDesc, csBuildTime);

 DbgOutput(VXN_INFO_TYPE_SUCCESS, _T("VXNAgent模块，版本描述：%s"), csDesc);
 DbgOutput(VXN_INFO_TYPE_SUCCESS, _T("VXNAgent模块，编译时间：%s"), csBuildTime);

 //输出参数赋值
 if(pbstrVersionDesc)
 {
  *pbstrVersionDesc = csVersionDesc.AllocSysString();
 }
}
STDMETHODIMP CVXNAgent::VXNGetData( BSTR* pbstrOutData)
{
        HardwareInfo hardwareinfo;
 DWORD dwrunip = hardwareinfo.GetRunIP(BoxIP);
 unsigned char *b;
 b=(unsigned char *)&dwrunip;
 char a[32];
 _snprintf_s(a,32,"%u.%u.%u.%u",b[0],b[1],b[2],b[3]);
 CComBSTR aa = a;
 aa.CopyTo(pbstrOutData);
 return S_OK;
}