Question

I have this function inside my program:

void CBar::NavigateComplete2(IDispatch *pDisp, VARIANT *URL)
  {

try {
    UpdateBar(UpdateNavigateComplete);
} catch (...) {
    ASSERT(0);
}
  }

I need to have the URL value from URL->bstrVal from this function and to copy it to a global variable so that my other function can easily refer to it.

What is the appropriate way to do this? since my current method destroys the stability of my program..it crash all the time.

Answer 1

I’m not sure I understand the question or the motivation. If all you want to do is, as described in the question, copy the value of URL->bstrVal then the simplest way to to use a wrapper BSTR class for the global.

namespace { // keep global private to .cpp file
    CComBSTR globalURL;
}

void CBar::NavigateComplete2(IDispatch *pDisp, VARIANT *URL)
{
    if (URL != NULL && URL->vt == VT_BSTR)
        globalURL = URL->bstrVal;

Otherwise you should use a raw BSTR and copy it with SysAllocString (and don’t forget to SysFreeString it when you’re done with the global.

If you don’t copy the string (and only copy the pointer) the VARIANT‘s owner will destroy it giving you a global with a dangling pointer.