On Wed, Dec 17, 2014 at 03:07:26PM +0100, David Sterba wrote:
> On Fri, Dec 12, 2014 at 01:35:14PM +0100, Karel Zak wrote:
> > This is first step to make btrfs-progs build system more conventional
> > for userspace users and developers. All is implemented by small incremental
> > patches to keep things review-able.
>
> Thanks. I went through the patches and haven't found major problems. The
> changes are affecting build system and this will need a longer period
> before all distros have a chance to adapt to that, so I'm postponing it
> to 3.19.
Cool, I'll try to prepare next set of patches with automake.
BTW, I have good experience with build-system changes -- downstream
distributions (maintainers) are usually pretty flexible :-)
> > Note that there is also strange unused btrfs_convert_libs, btrfs_image_libs
> > and
> > btrfs_fragments_libs variables with things like "-lgd -lpng -ljpeg
> > -lfreetype".
> > I guess it's some legacy, right? I didn't touch these variables as I have no
> > clue about sense of this stuff.
>
> No, it's part of the macro magic. There are pattern rules that accept
> any source in the form btrfs-something.c and also pick the libraries for
> that from variable btrfs_something_libs:
>
> btrfs-%: $(objects) $(libs) btrfs-%.o
> @echo " [LD] $@"
> $(Q)$(CC) $(CFLAGS) -o $@ $(objects) $@.o $(LDFLAGS) $(LIBS)
> $($(subst -,_,$@-libs))
>
> This is for convenience, if this turns out to be hard to do with in
> combination
> with autotools, I don't insist on keeping it but it has simplified the
> Makefile
> significantly.
OK, so -ljpeg in the Makefile is just example, right?
Anyway, for these things is better to introduce extra autoconf
AC_ARG_VAR() variables, keep is empty by default and use it in
Makefile. The advantage is that the variables are documented and
visible by ./configure --help.
For example in util-linux we have many {SUID,DAEMON,SOLIB,...}_CFLAGS
and LDFLAGS for distributions that require extensions like -fPIE,
-Wl,-z,relro etc. The same is possible to do with $LIBS.
Karel
--
Karel Zak <k...@redhat.com>
http://karelzak.blogspot.com
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