[Buildroot] [PATCH 2 of 3 v2] dependencies: build a host-tar if no suitable tar can be found

[Michael S. Zick <minimod@morethan.org>]

On Thu December 8 2011, Michael S. Zick wrote:
> On Thu December 8 2011, Thomas De Schampheleire wrote:
> > On Tue, Dec 6, 2011 at 6:07 PM, Arnout Vandecappelle <arnout@mind.be> wrote:
> > > On Wednesday 23 November 2011 15:24:40 Thomas Petazzoni wrote:
> > >
> > >> > TAR is redefined to HOST_TAR, except when extracting host-tar (this
> > >
> > >> > is a chicken-and-egg problem), so that all packages use the host-tar
> > >
> > >> > if no suitable tar was found.
> > >
> > >>
> > >
> > >> I am still puzzled by the fact that tar is needed to extract this
> > >
> > >> host-tar, so there's like a chicken-and-egg problem. I understand that
> > >
> > >> the real host tar is used to extract the host-tar, which is then use to
> > >
> > >> extract all other packages. But that sounds really nasty to me.
> > >
> > >
> > > It's not so strange, it's like a compiler's canadian build. You need a
> > >
> > > compiler to compile the compiler, right?
> > >
> > >
> > > The way it is solved for tar is OK for me. I think adding support for
> > >
> > > cpio archives would just complicate things, because then host-tar
> > >
> > > can't use GENTARGETS anymore.
> > 
> > I don't think that's true. I started adding cpio support to
> > gentargets. Essentially, here is the code that needs modification:
> > 
> > # Define extractors for different archive suffixes
> > INFLATE.bz2  = $(BZCAT)
> > INFLATE.gz   = $(ZCAT)
> > INFLATE.tbz  = $(BZCAT)
> > INFLATE.tbz2 = $(BZCAT)
> > INFLATE.tgz  = $(ZCAT)
> > INFLATE.xz   = $(XZCAT)
> > INFLATE.tar  = cat
> > 
> > $(2)_EXTRACT_CMDS ?= \
> >         $$(if $$($(2)_SOURCE),$$(INFLATE$$(suffix $$($(2)_SOURCE)))
> > $(DL_DIR)/$$($(2)_SOURCE) | \
> >         $(TAR) $(TAR_STRIP_COMPONENTS)=1 -C $$($(2)_DIR) $(TAR_OPTIONS) -)
> > 
> > 
> > Although the inflate step already handles multiple suffices, the
> > extract does not yet.
> >

Is the inflate step being used for tar archives?

The reason I ask is because GNU-tar (and BSD-tar) will auto-detect
the compression method from the file and un-archive it without
a prior de-compression.

In fact, if the "host tar" is BSD-tar, then you can unpack *.iso9660
as if it was an archive.

Mike 
> > My current approach is this:
> > +INFLATE.cpio = cat
> > +
> > +EXTRACT.tar = $(TAR) $(TAR_STRIP_COMPONENTS)=1 -C $(1) $(TAR_OPTIONS) -
> > +EXTRACT.cpio = ( mkdir -p $(1) && cd $(1) && cpio -i )
> > 
> >  $(2)_EXTRACT_CMDS ?= \
> >         $$(if $$($(2)_SOURCE),$$(INFLATE$$(suffix $$($(2)_SOURCE)))
> > $(DL_DIR)/$$($(2)_SOURCE) | \
> > -       $(TAR) $(TAR_STRIP_COMPONENTS)=1 -C $$($(2)_DIR) $(TAR_OPTIONS) -)
> > +       $$(if $$(EXTRACT$$(suffix $$($(2)_SOURCE))),$$(call
> > EXTRACT$$(suffix $$($(2)_SOURCE)),$$($(2)_DIR)),$$(call
> > EXTRACT$$(suffix $$(basename $$($(2)_SOURCE))),$$($(2)_DIR))))
> > 
> > 
> > The only thing I'm struggling with is that cpio does not have a
> > --strip-components functionality. 
> >
> 
> Would: "--no-absolute-filenames" help on the cpio command?
> 
> If this will become a general purpose extract.cpio command, it
> should have that option even if it doesn't help in this case.
> 
> Many cpio archives do have absolute paths (like the initramFS
> archive) even if the GNU-TAR cpio archive does not.
> 
> Mike
> > As a result, the package is 
> > extracted in output/build/host-tar-1.26/tar-1.26 which is not right.
> > I don't directly know the name 'tar-1.26', because all I have is the
> > string 'host-tar-1.26'. I see two approaches:
> > * either try to strip of 'host' from $(2)_DIR
> > * or do something like 'mv * .' or 'find -maxdepth 1 -type d | xargs mv {} .'
> > 
> > Suggestions are much appreciated...
> > 
> > Thanks,
> > Thomas
> > _______________________________________________
> > buildroot mailing list
> > buildroot at busybox.net
> > http://lists.busybox.net/mailman/listinfo/buildroot
> > 
> > 
> 
> 
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