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

Calculating dependencies ... done!
Dependency resolution took 1.50 s (backtrack: 0/20).

[ebuild     U  ] dev-libs/json-c-0.19:0/5.1::gentoo [0.18:0/5.1::gentoo] USE="threads -doc -static-libs -test" CPU_FLAGS_X86="rdrand" 452 KiB

Total: 1 package (1 upgrade), Size of downloads: 452 KiB