This function replaces the internal rb_obj_gc_flags API. rb_gc_object_metadata
returns an array of name and value pairs, with the last element having
0 for the name.
we had been using a stub weak definition of `mprotect` in wasm/missing.c
so far, but wasi-sdk 23 added mprotect emulation to wasi-libc[^1], so the
emulation is now linked instead. However, the emulation doesn't support
PROT_NONE and fails with ENOSYS, so we need to avoid calling mprotect
completely on WASI.
[^1]: 7528b13170
For moving garbage collectors, we may want to combine liveliness checking
with reference updating for performance. This commit allows for non-weak
references to be passed into the callback function when weak_only is false.
Previously, generic ivars worked differently than the other global tables
during compaction. The other global tables had their references updated
through iteration during rb_gc_update_vm_references. Generic ivars updated
the keys when the object moved and updated the values while reference
updating the object. This is inefficient as this required one lookup for
every moved object and one lookup for every object with generic ivars.
Instead, this commit changes it to iterate over the generic ivar table to
update both the keys and values.
- Split static recipes to depend file.
- Modify makefile configurations in the block to `create_makefile`.
- Expand rust sources in extconf.rb instead of GNU make extension.
TODO: pass `CARGO_TARGET_DIR` without shell syntax.
Depending on the allocator, `malloc_usable_size` may be very cheap or quite
expensive. On `macOS` for instance, it's about as expensive as `malloc`.
In many case we call `objspace_malloc_size` with as size we initially
requested as `hint`. The real usable size may be a few bytes bigger,
but since we only use that data to feed GC heuristics, I don't think
it's very important to be perfectly accurate.
It would make sense to call `malloc_usable_size` after growing a String
or Array to use the extra capacity, but here we don't do that, so
the call isn't worth its cost.
rb_darray_insert could trigger a GC, which would cause problems if it
freed pages while a new page was being inserted.
For example, the following script fails:
GC.stress = true
GC.auto_compact = :empty
10.times do
GC.verify_compaction_references(expand_heap: true, toward: :empty)
end
It errors out with:
'GC.verify_compaction_references': malloc: possible integer overflow (8*18446744073709551603) (ArgumentError)
If we try to use GET_PAGE_HEADER, it can trigger the read barrier. If we
try to align on the slot then we end up unlocking the heap page of a
lower memory address.
