tar(1) unsatisfied with gtar(1) files (pkgsrc)

[tlaronde%polynum.com@localhost]

Hello,

I would not qualify this as a bug but others may encounter the problem
and perhaps someone could find what the "fix" is---and more importantly:
what to fix?

When extracting (pkgsrc) a *.tar.xz file, namely gcc-7.3.0.tar.xz, there
are a lot of warnings from tar:

	tar: File extended headers posix ustar archive. Extracting as plain
	files. Following files might be in the wrong directory or have wrong
	attributes.

Doing the comparison:

$ xz -dc gcc-7.3.0.tar.xz |tar tf -

vs

$ xz -dc gcc-7.3.0.tar.xz |gtar tf -

it seems clear that the file was tar'ed with gtar(1) which doesn't
complain with what is fed to it.

I have tried with other source files (disfiles from pkgsrc) and it seems
to be the only one producing this.

Does anybody know if gtar(1) creates some gtar special format and if
there is a mean to detect it? Or are there "extensions" that are not
recognized by the system tar(1)?

For the record, it doesn't seem that even untar'ed with tar(1) there is
a problem, at least for the compilation (for files only used as
sources, permissions and ownership or other attributes having no
impact; for backups, it would probably not the same...).

FWIW.
-- 
        Thierry Laronde <tlaronde +AT+ polynum +dot+ com>
                     http://www.kergis.com/
                       http://www.sbfa.fr/
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