|The main COMPILE-TIME DEFINES to keep in mind when reading the host*.c
|source file are these:
|CURLRES_IPV6 - this host has getaddrinfo() and family, and thus we use
|that. The host may not be able to resolve IPv6, but we don't really have to
|take that into account. Hosts that aren't IPv6-enabled have CURLRES_IPV4
|CURLRES_ARES - is defined if libcurl is built to use c-ares for asynchronous
|name resolves. It cannot have ENABLE_IPV6 defined at the same time, as c-ares
|has no ipv6 support. This can be Windows or *nix.
|CURLRES_THREADED - is defined if libcurl is built to run under (native)
|Windows, and then the name resolve will be done in a new thread, and the
|supported asynch API will be the same as for ares-builds.
|If any of the two previous are defined, CURLRES_ASYNCH is defined too. If
|libcurl is not built to use an asynchronous resolver, CURLRES_SYNCH is
|The host*.c sources files are split up like this:
|hostip.c - method-independent resolver functions and utility functions
|hostasyn.c - functions for asynchronous name resolves
|hostsyn.c - functions for synchronous name resolves
|hostares.c - functions for ares-using name resolves
|hostthre.c - functions for threaded name resolves
|hostip4.c - ipv4-specific functions
|hostip6.c - ipv6-specific functions
|The hostip.h is the single united header file for all this. It defines the
|CURLRES_* defines based on the config*.h and setup.h defines.