On Thu, Aug 10 2023, Robert Pluim wrote:

> Hmm. Maybe putting it in `deactivate_process' is better (not that Iʼve
> tested 😺)

After a night of sleep, it occurred to me that this could also be
considered a problem of incomplete initialization of the
fd_callback_info[fd] struct.

So I wondered who is supposed to initialize it.  Unfortunately, there is
half a dozen of add_<foo>_fd functions that set various bits, some call
each other, some duplicate code.  None of them sets the waiting_thread
slot.  And there is no single point that clears everything out (except
init_process_emacs).

I also discovered that recompute_max_desc considers an fd unused if the
.flags field is zero.  Luckily, recompute_max_desc is only called in
three places: delete_write_fd, delete_keyboard_wait_descriptor and
deactivate_process.  The call in deactivate_process seems redundant as
it calls the other two anyway.  It seems easier to re-initialize the
struct when it becomes unused than to initialize it when it is used the
first time.

So I'm proposing the patch below that moves the re-initialization to one
single place, namely: recompute_max_desc.

Helmut