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It would be nice to be able to invalidate objects that should no longer be
used.
The API could be similar to `free()` in C, but it should also allow
individual fields to be invalidated.
For some types of objects it can actually be done without additional
meta-data (but it would still be checked at time of access, unless a GC run
happens):
* short/int/long (that are not signed/unsigned)
* integers that don't use the full unsigned/singed range.
* non-nullable objects.
* references (if the platform doesn't use the full address space,
so there's room for a sentinel value such as `(void *)-1`)
* bool
* padding in structs (assuming that it is required to be 0)
I.e. all except for the following types (and only when there's no
alignment padding):
* byte
* unsigned (short/int/long)
* signed (short/int/long)
Object invalidation for "all-bits-used" types
---------------------------------------------
How to support invalidation of the "all-bits-used" types,
i.e. full-range byte/unsigned/signed.
Solution 1: A small metadata bit flag could be inserted:
struct Thing {
unsigned char _SLUL_infobyte;
unsigned long l1;
unsigned long l2;
}
Solution 2: Track uninitialized data in each arena chunk?
Solution 3: Track all "all-bits-used" types in each arena chunk?
Related: "Uninitialized" and Sentinel values
--------------------------------------------
It would actually be quite nice to have 2 different values:
* Invalidated (including uninitialized)
* `none`
Note that `none` is trickier, because a struct can be none, but its
fields can also be none. And structs can be nested.
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