.PRECIOUS: Preserving Libraries Against Removal due to Interrupts

Normally, if you interrupt make in the middle of a target, the target file is removed. For individual files this is a good thing, otherwise incomplete files with brand new modification times might be left in the directory. For libraries that consist of several members, the story is different. It is often better to leave the library intact, even if one of the members is still out-of-date. This is especially true for large libraries, especially since a subsequent make run picks up where the previous one left off--by processing the object file or member whose processing was interrupted.

.PRECIOUS is a special target that is used to indicate which files should be preserved against removal on interrupts; make does not remove targets that are listed as its dependencies. If you add the line:

.PRECIOUS:  librpn.a

to the makefile shown above, run make, and interrupt the processing of librpn.a, the library is preserved.