Re: makefiles: obj vs. objtree

[Michal Marek <mmarek@suse.cz>]

On 18.2.2010 03:27, Randy Dunlap wrote:
> Can someone clarify the difference(s) in these variables, please?
> 
> Documentation/kbuild.txt says about objtree:
> 
> $(objtree) is the directory where output files are saved.
> The output directory is often set using "O=..." on the commandline.
> 
> 
> Documentation/makefiles.txt says about obj:
> 
>     $(obj)
> 	$(obj) is a relative path which points to the directory
> 	where the target is saved. Always use $(obj) when
> 	referring to generated files.
> 
> 
> These appear to be the same to me, but let me be more specific:

$(objtree) is the toplevel build directory (as the doc says the
directory you specify with O=).
$(obj) is the directory below $(objtree) where the targets of the
current Makefile are saved:

$ make O=/build/dir
$(objtree) == /build/dir
$(obj) == /build/dir/fs in fs/Makefile


> In some cases (or places), Documentation/DocBook/Makefile uses
> $(obj) and other cases/places, it uses $(objtree).
> Does it have these correct, or should some of them be fixed?

$(objtree)/Documentation/DocBook could be written as $(obj) in
Documentation/DocBook/Makefile.

hth,
Michal