That seems to be a good idea. I’ve done this along with adding automatic compaction when blocks are shrunk and now were around 90% of croaring’s speed on this benchmark 
.
Of course that means 2 allocations instead of one and a slightly less happy deinit. But I can accept that.
zig build bench -Doptimize=ReleaseFast
$ zig build bench -Doptimize=ReleaseFast
--------------------------------------------------
overall:
--------------------------------------------------
CRoaring: 11430 ops 20.698ms 0.55MB ops/sec
ZRoaring: 11430 ops 22.894ms 0.50MB ops/sec
ratio -- 0.90 🥔
--------------------------------------------------
individual ops: speed=ops/sec
--------------------------------------------------
op cr speed zr speed # ratio
--------------------------------------------------
clear 1.62MB 35.25MB 240 21.82 ⚡
run_optimize 0.61MB 0.60MB 365 0.99 👍🏻
shrink_to_fit 4.17MB 1.20MB 330 0.29 💩
portable_serialize 0.70MB 0.94MB 105 1.34 ⚡
frozen_serialize 2.31MB 2.28MB 85 0.99 👍🏻
minimum 32.69MB 34.56MB 580 1.06 👍🏻
maximum 14.55MB 7.65MB 585 0.53 💩
add 12.09MB 10.37MB 2200 0.86 🥔
rank 10.29MB 9.69MB 25 0.94 👍🏻
select 8.72MB 8.43MB 30 0.97 👍🏻
contains 22.46MB 22.67MB 580 1.01 👍🏻
add_many 2.52MB 2.86MB 915 1.13 ⚡
add_range_closed 2.37MB 2.29MB 1545 0.96 👍🏻
contains_range 16.02MB 17.40MB 570 1.09 ⚡
range_cardinality 6.67MB 5.15MB 5 0.77 🥔
remove 11.65MB 11.98MB 630 1.03 👍🏻
and 0.34MB 0.41MB 420 1.22 ⚡
or 196.69kB 219.31kB 305 1.12 ⚡
xor 157.98kB 180.81kB 375 1.14 ⚡
andnot 217.86kB 0.33MB 320 1.50 ⚡
lazy_or 161.72kB 239.00kB 250 1.48 ⚡
or_inplace 0.32MB 0.34MB 390 1.05 👍🏻
and_inplace 140.05kB 142.59kB 60 1.02 👍🏻
is_subset 134.90kB 144.89kB 180 1.07 ⚡
equals 26.55MB 6.86MB 30 0.26 💩
and_cardinality 0.74MB 1.05MB 40 1.42 ⚡
or_cardinality 0.79MB 0.93MB 45 1.18 ⚡
xor_cardinality 0.95MB 0.94MB 35 0.99 👍🏻
andnot_cardinality 0.81MB 0.96MB 20 1.18 ⚡
jaccard_index 0.88MB 1.06MB 40 1.20 ⚡
or_many 19.59kB 12.23kB 130 0.62 💩