asdf hacks
System “asdf-hacks” adds a dynamic dispatch bits for system
dependencies and component names. Classes dynamic-system for the
system and dynamic-source for the file are created to present the
mechanism.
When system dependency is a string and it starts with “xxx-” then
dependency is replaced to either “host-” or “native-” dependent on
*whoosh* variable. Of course we could simply replace “xxx-” with
*whoosh* value to have more fexible behavior.
When source file is named “heroes” then it is replaced with either “might” or “magic”.
dsys
System “dsys” shows how to use asdf-hacks. Notice, that we’ve put
there eval-when to load asdf-hacks beforehand what clearly shows
that defsystem-depends-on usefullness is very limited - asdf doesn’t
have its own reader so it can’t load the system definition if it has a
package reference which is not defined (in our case
asdf-hacks:dynamic-system).
Important options to defsystem are :class and
:default-component-class. System depends on “xxx-cl” and has a file
“heroes”, what means, that if *whoosh* is T, then system depends on
“host-cl” and “might” while when *whoosh* is NIL then system depends
on “native-cl” and “magic”. File “normal” is loaded normally :).
notes
Notice, that changing *whoosh* after loading “dsys” and loading “dsys”
again will work poorly and is a bad idea, because then you will have a
mashup of both system files in a single image.