On Friday, 17 January 2014 at 13:31:10 UTC, Robert wrote:
On Friday, 17 January 2014 at 08:46:33 UTC, Kagamin wrote:
1. there're two typical usage patterns of signals: you mostly
have 0 or 1 slots attached, so it would be nice if having one
slot wouldn't require allocation. SlotsArray should be
probably a tagged union of SlotImpl and SlotImpl[]. Is it
worth an effort?
Well it depends. One of my goals was to minimize memory usage
of an empty signal, using a tagged union would increase the
space used by an empty signal. (A slot consists of 3 pointers +
memory for the tag, the array consists of a pointer and a
length)
We can infer the tag from one of the pointers and use two other
for the array. I suppose, _funcPtr can't be null in a
meaningfully filled slot, so if it's not null, that's a slot,
otherwise _dataPtr and _obj are array's ptr and length
respectively. So it's only 1.5 bigger.
2. why InvisibleAddress is so big? Isn't it enough to just
negate it?
For 64 bit yes, but not for 32 bit. InvisibleAddress handles
both.
False pointers. I'm afraid, 32-bit has them any way.
3. I think, it's important to document, that a weak connection
can be destroyed before it becomes logically unneeded. It's an
important and non-trivial caveat.
How is this supposed to happen?
If you attach an object to a slot and then lose the last
reference to it.
