On Thu, May 9, 2013 at 9:13 AM, René Scharfe <rene.scharfe@xxxxxxxxxxxxxx> wrote: > Test 2 of t5004 checks if a supposedly empty tar archive really > contains no files. 24676f02 (t5004: fix issue with empty archive test > and bsdtar) removed our commit hash to make it work with bsdtar, but > the test still fails on NetBSD and OpenBSD, which use their own tar > that considers a tar file containing only NULs as broken. > > Here's what the different archivers do when asked to create a tar > file without entries: > > $ uname -v > NetBSD 6.0.1 (GENERIC) > $ gtar --version | head -1 > tar (GNU tar) 1.26 > $ bsdtar --version > bsdtar 2.8.4 - libarchive 2.8.4 > > $ : >zero.tar > $ perl -e 'print "\0" x 10240' >tenk.tar > $ sha1 zero.tar tenk.tar > SHA1 (zero.tar) = da39a3ee5e6b4b0d3255bfef95601890afd80709 > SHA1 (tenk.tar) = 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c > > $ : | tar cf - -T - | sha1 > da39a3ee5e6b4b0d3255bfef95601890afd80709 > $ : | gtar cf - -T - | sha1 > 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c > $ : | bsdtar cf - -T - | sha1 > 34e163be8e43c5631d8b92e9c43ab0bf0fa62b9c > > So NetBSD's native tar creates an empty file, while GNU tar and bsdtar > both give us 10KB of NULs -- just like git archive with an empty tree. > Now let's see how the archivers handle these two kinds of empty tar > files: > > $ tar tf zero.tar; echo $? > tar: Unexpected EOF on archive file > 1 > $ gtar tf zero.tar; echo $? > gtar: This does not look like a tar archive > gtar: Exiting with failure status due to previous errors > 2 > $ bsdtar tf zero.tar; echo $? > 0 > > $ tar tf tenk.tar; echo $? > tar: Cannot identify format. Searching... > tar: End of archive volume 1 reached > tar: Sorry, unable to determine archive format. Missing "echo $?" output. > $ gtar tf tenk.tar; echo $? > 0 > $ bsdtar tf tenk.tar; echo $? > 0 > > NetBSD's tar complains about both, bsdtar happily accepts any of them > and GNU tar doesn't like zero-length archive files. So the safest > course of action is to stay with our block-of-NULs format which is > compatible with GNU tar and bsdtar, as we can't make NetBSD's native > tar happy anyway. > > We can simplify our test, however, by taking tar out of the picture. > Instead of extracting the archive and checking for the non-presence of > files, check if the file has a size of 10KB and contains only NULs. > This makes t5004 pass on NetBSD and OpenBSD. > > Signed-off-by: Rene Scharfe <rene.scharfe@xxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html