Cross-compiling perl

Hints are pre-defined values for variables, used when testing for particular value is impossible or such test should be avoided for whatever reasons.

Hints for perl-cross are stored under cnf/hints. Unless told otherwise with --hints, configure will load hints for $archname and $osname. A build that ends up creating $prefix/lib/perl5/5.24.0/x86_64-linux likely starts by loading cnf/hints/x86_64_linux and cnf/hints/linux.

Hints in perl-cross are not just regular shell scripts. They are filtered with sed and generally should not contain anything but

	variable="properly quoted value"

lines, which are internally converted to

	hint variable "properly quoted value"

and then executed.

Difference between mainline perl hints and perl-cross hints

Hint files supplied with the mainline perl (hints/ in the source tree) and not used by perl-cross configure. This is mainly because mainline perl hint files are expected to take care of preset variables and command line options by themselves, in style with the rest of Configure, while perl-cross configure handles such things in a different manner. These two systems do not mix very well.

Another reason is that mainline hints are allowed to run tests and look around in the host system, which is a good way to get into troubles during cross builds.

Mainline hints use (os).sh naming scheme and must determine other aspects of target configuration internally using conditionals. In contrast, perl-cross uses passive hint files with nothing but variable assignments in them.

perl-cross does not support callbacks and per-file cflags from the mainline hints. Callbacks are not really necessary in non-interactive mode because all user-set values are known from the very start, and cctype hints partially solve the problem of compiler related settings.