[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, 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 $$($(2)_DIR) $(TAR_OPTIONS) -)
> 
> 
> Although the inflate step already handles multiple suffices, the
> extract does not yet.
> 
> My current approach is this:
> +INFLATE.cpio = cat
> +
> +EXTRACT.tar = $(TAR) $(TAR_STRIP_COMPONENTS)=1 -C $(1) $(TAR_OPTIONS) -
> +EXTRACT.cpio = ( mkdir -p $(1) && cd $(1) && cpio -i )
> 
>  $(2)_EXTRACT_CMDS ?= \
>         $$(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
> 
>