On Mon, Nov 19, 2001 at 10:58:55AM +0000, Dave Mitchell wrote:
> Presumably we should have a small, *fixed* number of private bits in
> the flags word available for use by vtable implementors (ie to stop
> people getting carried away with the notion that they can steal any
> bits which do not otherwise appear to have been allocated yet ;-)
If you look at the way I've done it in the code and the docs,
vtable implementors have a macro representing the start of private flags.
I've reserved 8 flags, starting the private stuff at 9. If we need to reserve
more, we rewrite the macro, and all the vtable stuff should recompile, unless
they're using an reasonable number of bits. There will, of course, be warnings
and guidelines about what constitutes "reasonable" in the documentation; in
the worst case, they'll have to use the flag structure we provide as "fast"
flags and store a separate flags field in their data structure for
less-commonly accessed stuff.
--
The best book on programming for the layman is "Alice in Wonderland";
but that's because it's the best book on anything for the layman.
- Alan Perlis
