notably key id doesn’t have to be recalculated every time, cheaper checks should come first, name equality check is cheaper as well 

skipping over last/root label returns a pointer to a memory after domain name, this is unsafe

this doesn’t guarantee valid cache after crash,
but then it’s a cache. most of the time on cold
cache is spent on fsyncing as it’s done per each
commit (=> resolved query)

this also fails if the timeout timer cannot be started,
as it would wait for undefined time otherwise

amalgamated build concatenates all files into a single .c file to
allow compiler see all symbols and produce possibly smaller code.
for binary distributions this is what you want, as it's faster but
may consume more memory during compilation.
it however cannot do incremental builds.