Re: Order-only dependencies don't work

[Earnie Boyd]

Posted on DATE by AUTHOR Daniel Olivier
> Isn't this supposed to work?
> obj_dir lib_dir :
>       [ -d $@ ] || mkdir -p $@
> obj_dir/%.o : src_dir/%.c | obj_dir
> #     [ -d obj_dir ] || mkdir -p obj_dir # this does work
>       touch $@
> lib_dir/%.b : obj_dir/obj1.o obj_dir/obj2.o | lib_dir
>       touch $@
> obj_dir/obj2.o : src_dir/obj2.c
> obj_dir/obj1.o : src_dir/obj1.c
> lib_dir/test.b : obj_dir/obj2.o obj_dir/obj1.o
> It builds fine the first time, but for some reason. If I attempt to make
a
> second time, because the obj_dir directory (dependency) is newer than
the
> (target) obj1.o, the rule is re-run, causing the "compiler" (touch in
this
> simplified case) and "linker" to be re-invoked once each, despite the
fact
> that the this is an order-only dependency.

The directory that contains the file will always be newer than the oldest
file in the directory.  The directory timestamp is updated when the
directory contents changes.

Hardcoding the directories as you have above isn't good design, IMNSHO.

Earnie