Re: Support for out-of-tree build

[Rich Felker <dalias@libc.org>]

On Mon, Nov 30, 2015 at 01:01:57PM +0100, Szabolcs Nagy wrote:
> * Petr Hosek <phosek@chromium.org> [2015-11-30 01:30:30 +0000]:
> > On Sun, Nov 22, 2015 at 6:56 AM Szabolcs Nagy <nsz@port70.net> wrote:
> > 
> > > * Petr Hosek <phosek@chromium.org> [2015-11-19 00:22:09 +0000]:
> > > >
> > > > +$(ALL_LIBS): | lib/
> > > > +$(ALL_TOOLS): | tools/
> > > > +$(CRT_LIBS:lib/%=$(objdir)/crt/%): | $(objdir)/crt/
> > > > +$(OBJS) $(LOBJS): | $(sort $(dir $(OBJS)))
> > > > +$(GENH): | $(objdir)/include/bits/
> > > > +$(GENH_INT): | $(objdir)/src/internal/
> > > > +
> > >
> > > one more comment:
> > > tools/ is now used for both sources and outputs,
> > > i think it can be used for sources only by moving
> > > the tools outputs under obj/ (so tools/ does not
> > > need to be created out of tree, only obj/ and lib/)
> > >
> > 
> > Do you mean moving the tools output directly to obj/ or obj/tools?
> 
> i think obj/ is ok.
> 
> (i like flatter dir hierarchy if only a small number
> of files are involved.)

I'm not sure if it makes a difference, but conceptually right now obj
is intermediate files for build, and lib and tools contain the actual
files intended to be installed. The one exception to this is headers,
which are split between the $(srcdir)/include,
$(srcdir)/arch/$(ARCH)/bits, and obj/include/bits, making the latter
the one installed file from obj.

I don't think we have to resolve this at the same time as out-of-tree,
but I'd moderately prefer putting all the installable files under one
directory structured just like an install prefix, to make it easy to
use them in-place without installing. This worked historically with
the in-tree build thanks to the (very problematic, otherwise) bits
symlink.

Rich