Where is zero BSTR used?

Question

It is at least common practice to process a null BSTR (null pointer WCHAR *) as an empty string and design all the codes that control the BSTR, respectively. The answers to this question say the same thing.

Where is this practice documented? Is there an official document describing this agreement?

Answer 1

Well, the link provided in the accepted answer to this question is an article by Eric Lippert, Eric's Complete Guide to BSTR Semantics . Although this will definitely not be official documentation, Lippert is a well-known authority in COM (especially in scripting).

However, the official documentation has this to say:

A BSTR without data items is an empty BSTR or NULL BSTR. An empty BSTR indicates the current but zero data value. NULL BSTR indicates a data value that is missing.

, BSTR , ( , 2 - ). , , , . , , , BSTR.

Answer 2

, , , . , BSTR MSDN .

, MSDN:

• SysFreeString , BSTR null, .
• SysStringLen , null BSTR .
• SysStringByteLen ; null .

:

• SysReAllocString , , *pbstr - null.
• SysReAllocStringLen , , *pbstr - null.