bug#66117: 30.0.50; `find-buffer-visiting' is slow when opening large number of buffers

[Ihor Radchenko <yantar92@posteo.net>]

Eli Zaretskii <eliz@gnu.org> writes:

>>   #define BVAR(buf, field) (buffer_overrides->field ## _ == UNSET ?\
>>                               (buf)->field ## _ :\
>>                              buffer_overrides->field ## _)
>> 
>>   and replace the loop with simply setting buffer_overrides slot.
>
> So for starters, we make each BVAR more expensive, i.e. make Emacs
> uniformly slower (because we call BVAR all over the place).

Yes, although I do not believe that it will have large impact in
practice. It is just an extra == comparison.

> ... And then
> I'm not sure I understand how buffer_overrides will get the values of
> those temporary bindings without having to use the same loops when we
> have let-binding within another one.  Also, what about threads?

Just as any other global state variable - via `specbind'. Entering inner
let will push the previous value into specpdl and recover it upon
exiting.

Threads work similarly, maintaining their own local specpdl queue heads
that make sure that global state is recorded and rewinded as needed.

-- 
Ihor Radchenko // yantar92,
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