>     Here is a more-detailed review of the latest patch you sent.
>
>     > -      int i = 0, aligned = (intptr_t) ABLOCKS_BUSY (abase);
>     > +      int i = 0, aligned = (ABLOCKS_BUSY (abase) != NULL);
>
>     Not needed for Windows 64.  The change slows the code down a bit, and
>
>
> Prove it.

I compiled it both ways (x86-64 GCC 4.6.2), and the "!= NULL" version
has an extra "cmpl" instruction, so it is indeed a bit fatter.