These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 0.98 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/crc32c-1.1.2-r2::gentoo  USE="-test" 30 KiB
[ebuild  N     ] app-arch/snappy-1.2.2-r1:0/1.1::gentoo  USE="-test" CPU_FLAGS_X86="avx avx2" 1083 KiB
[ebuild  N     ] dev-libs/leveldb-1.23-r6:0/1::gentoo  USE="snappy tcmalloc -test" 238 KiB

Total: 3 packages (3 new), Size of downloads: 1349 KiB