Comment 3 for bug 1117466

I have checked and it doesn't seem to be LOCATE-SYSTEM. I loaded ASDF on both ACL and on SBCL, and the results of LOCATE-SYSTEM afterwards are the same:

ACL:

CL-USER> (push "/Users/rpg/lisp/asdf/" asdf:*central-registry*)
("/Users/rpg/lisp/asdf/" "home:lisp;franz-clx;" "~/lisp/asdf-systems/"
 "~/lisp/asdf-install-systems/systems/" "~/lisp/asdf-systems/"
 "~/lisp/asdf-install-systems/systems/")
CL-USER> (asdf:load-system "asdf")
; Loading /Users/rpg/lisp/asdf/asdf.asd
; Fast loading
; /Users/rpg/.cache/common-lisp/acl-8.2-macosx-x64/Users/rpg/lisp/asdf/build/asdf.fasl
; Upgrading ASDF from version 2.23.7 to version 2.28
T
CL-USER> (asdf::locate-system "asdf")
T
NIL
#P"/Users/rpg/lisp/asdf/asdf.asd"
NIL
NIL

SBCL:
....
CL-USER> (asdf::locate-system "asdf")
T
NIL
#P"/Users/rpg/lisp/asdf/asdf.asd"
NIL
NIL