Re: Order-only prerequisites

[Henrik Carlqvist]

> Consider this makefile:
> 
> .PHONY: a b
> a:; @echo a
> b:; @echo b
> b: | a

Your problem with this Makefile is that it never creates any files a or b.
This means that your order only prerequisite on a allways has to be made.

> % make b a
> a
> b
> make: Nothing to be done for 'a'.
> 
> Correct order, but the last message seems strange.

First as a (order-only) prerequisite for b, a is made. Then b is made. Then
make was asked to make a but it does remember that a already has been made and
prints out that nothing to be done.

If  your Makefile would have created the file a the order-only prerequisite
would have made sense. It would then mean that b would depend upon the
existance of a but it would not care about the timestamp of a. So if a exist
and is newer than b there is no need to remake b of a is a order-only
prerequisite.

> If so, is there another way to achieve what I want?

This totally depends upon what you want.

regards Henrik