When a prerequisite is found through directory search, regardless of type
(general or selective), the pathname located may not be the one that
make actually provides you in the prerequisite list. Sometimes
the path discovered through directory search is thrown away.
make uses to decide whether to keep or abandon a
path found via directory search is as follows:
makedoesn’t need to rebuild the target then you use the path found via directory search.
makemust rebuild, then the target is rebuilt locally, not in the directory found via directory search.
This algorithm may seem complex, but in practice it is quite often exactly what you want.
Other versions of
make use a simpler algorithm: if the file does
not exist, and it is found via directory search, then that pathname is
always used whether or not the target needs to be built. Thus, if the
target is rebuilt it is created at the pathname discovered during
If, in fact, this is the behavior you want for some or all of your
directories, you can use the
GPATH variable to indicate this to
GPATH has the same syntax and format as
VPATH (that is, a
space- or colon-delimited list of pathnames). If an out-of-date target
is found by directory search in a directory that also appears in
GPATH, then that pathname is not thrown away. The target is
rebuilt using the expanded path.