Re: [PATCH] btrfs: set include path relatively

[David Sterba <dsterba@suse.cz>]

On Fri, Oct 13, 2017 at 04:01:31PM +0900, Naohiro Aota wrote:
> 2017-10-12 21:38 GMT+09:00 David Sterba <dsterba@suse.cz>:
> > On Thu, Oct 12, 2017 at 11:22:24AM +0900, Naohiro Aota wrote:
> >> Currently, gcc is passed the include directory with full path. As a result,
> >> dependency files (*.o.d) also record the full path at the build time. Such
> >> full path dependency is annoying for sharing the source between multiple
> >> machines, containers, or anything the path differ.
> >>
> >> And this is the same way what other program using autotools e.g. e2fsprogs
> >> is doing:
> >>
> >> $ grep top_builddir Makefile
> >> top_builddir = .
> >> CPPFLAGS = -I. -I$(top_builddir)/lib -I$(top_srcdir)/lib
> >> BUILD_CFLAGS = -g -O2  -I. -I$(top_builddir)/lib -I$(top_srcdir)/lib -DHAVE_CONFIG_H
> >> <snip>
> >
> > Makes sense for the header files. TOPDIR is also used for linking, can
> > it cause similar problems, where the library search path is set as -L$(TOPDIR) ?
> 
> Since both "TOPDIR := $(shell pwd)" and -L$(TOPDIR) is evaluated at
> the build time,
> it never cause problem on linking itself. What the problem with
> dependency files is persisting
> the full path into the dep files. We generate the dep files only for
> objects (%.o.d rule)
> 
> Well, it's ok to use "-L." here, and it's the same way with autotools does.
> 
> > I wonder if we should do the same as in the example above and set
> > default value of TOPDIR to '.', instead of `pwd`.
> 
> TOPDIR is also used by library-test{,.static}. They run gcc in a
> temporary directory.
> Thus, TOPDIR here should be absolute.

I've added another variable with absolute path to make library-test work
and updated your patch so we can use TOPDIR = .