Question

I have the following pointer:

BSTR *PREVIOUS;

And I want make a new copy to:

BSTR *NEW;

I want to copy the CONTENTS/DATA (that PREVIOUS is pointing) from PREVIOUS to NEW.

I’ve just tried the following command, but it doesn’t work:

memcpy(NEW,PREVIOUS,SysStringByteLen(*PREVIOUS));

I dont see any error when compiling because I am working on ATL COM environment. Please help. Thank you!

Answer 1

BSTR is itself already a pointer, you should almost always use just a plain BSTR, not a BSTR* (which is a pointer to a BSTR). Ordinarily, you would copy a BSTR with SysAllocString:

BSTR NEW = SysAllocString(PREVIOUS);

If you really do have a pointer to a BSTR (such as via a function’s out parameter), then you add a layer of indirection:

BSTR *PREVIOUS = ...;  // This must point to a valid BSTR
BSTR *NEW = ...;  // This must also point to a valid BSTR
*NEW = SysAllocString(*PREVIOUS);