Re: (b)make: generating multiple targets at once

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> The traditional, correct way is
> 
> 	dst/foo dst/bar: src/foo src/bar
> 		gen foo bar
> 
But if dst/foo is up-to-date wrt. src/foo and dst/bar is up-to-date 
wrt. src/bar, but the foo pair is older than the bar pair (i.e., 
dst/foo is older than src/bar), then dst/foo is considered out-of-date 
(wrt. src/bar, which shouldn't count) and gen is run, no?

> 	dst/foo: src/foo src/bar
> 		gen foo bar
> 	dst/bar: dst/foo
> 		@true
(I'm not sure why the true recipie is needed.)
That suffers from the same outcome as above.

May be I need to re-phrase what I'm seeking. Think of a compiler able to 
efficiently compile several source files (to individual object files) 
in one invocation (even skipping those which are up-to-date anyway) 
but needing ages to start up. Once I decide to start the beast, It doesn't 
matter if I give it more input than needed, but I never want to start it 
in case I can get away without.