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

Calculating dependencies ... done!
Dependency resolution took 1.16 s (backtrack: 0/20).

[ebuild  N     ] dev-libs/libaio-0.3.113_p8::gentoo  USE="-static-libs -test" 74 KiB
[ebuild  N     ] dev-build/b2-5.5.3::gentoo  USE="-examples" 1198 KiB
[ebuild  N     ] dev-cpp/gflags-2.2.2-r1:0/2.2::gentoo  USE="-static-libs -test" 97 KiB
[ebuild  N     ] app-arch/lz4-1.10.0-r1:0/1.10.0-meson::gentoo  USE="-static-libs -test" 379 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-cpp/fast_float-8.0.2::gentoo  USE="-test" 119 KiB
[ebuild  N     ] dev-libs/double-conversion-3.4.0:0/3::gentoo  USE="-test" 6871 KiB
[ebuild  N     ] dev-cpp/glog-0.6.0-r1:0/1::gentoo  USE="gflags libunwind -llvm-libunwind -test" 189 KiB
[ebuild  N     ] dev-libs/boost-1.91.0-r2:0/1.91.0::gentoo  USE="bzip2 context nls python stacktrace zlib -debug -doc -icu -lzma -mpi -numpy -test -test-full -tools -zstd" PYTHON_TARGETS="python3_14 -python3_12 -python3_13" 199785 KiB
[ebuild  N     ] dev-cpp/folly-2025.04.14.00-r2:0/2025.04.14.00::gentoo  USE="(-io-uring) -llvm-libunwind -test" 4197 KiB

Total: 10 packages (10 new), Size of downloads: 213987 KiB

The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
# required by dev-cpp/folly-2025.04.14.00-r2::gentoo
# required by =dev-cpp/folly-2025.04.14.00-r2 (argument)
>=dev-cpp/glog-0.6.0-r1 gflags