(A==B)==(X==Y)

re: (A==B)==(X==Y)

Jonathan Perret — Fri, 21 Sep 2007 19:09:40 GMT

Until VB.NET, VB still had the Eqv boolean operator. Which allowed you to write :

(A=B) Eqv (X=Y)

The result being strictly the same but perhaps slightly more readable ?

re: (A==B)==(X==Y)

Mike Stall - MSFT — Fri, 21 Sep 2007 17:58:46 GMT

I should have been clearer, when I said:

"This asserts that either you have a pointer to a non-zero-length buffer or you don't have anything at all."

Lots of functions tend to take a buffer as (pointer, size), and optionally allow the buffer to be empty. (Eg, maybe it will write something to the buffer if provided).

How do you supply an empty buffer? Just a null pointer? Just a 0 size? To be defensive, it's nice to require both pBuffer == NULL and cbLength == NULL.

So then you have 2 valid options:

pBuffer == NULL && cbLength == NULL; // empty buffer

pBuffer != NULL && cbLength != NULL; // valid buffer

Rather than assert

Assert((pBuffer == NULL && cbLength == NULL) ||

(pBuffer != NULL && cbLength != NULL));

I think it's easy to say

Assert((pBuffer == NULL) == (cbLength == NULL));

re: (A==B)==(X==Y)

Alois Kraus — Fri, 21 Sep 2007 10:53:46 GMT

I am no compiler but what about

pBuffer = NULL and cbLength = NULL?

Assert((true) == (true));

Assert(true); // nothing happens althouth the input is bad.

If I read this right it will slip through your Assert.

Yours,

Alois Kraus