Subject: bug#19614: make dist exits succesfully even when tar exits with error

From: Eric Blake <[email-masked]>
Date: Fri, 16 Jan 2015 09:47:51 -0700

On 01/16/2015 08:01 AM, Dimitrios Apostolou wrote:
> (Please keep me CC'd as I'm not subscribed.)

In general, GNU list policy is to reply-to-all, precisely so you don't
have to leave disclaimers like that :)

> 
> Hello list,
> 
> as the title says, I believe running "make dist" should fail when tar
> fails. The problem is that because there is a shell pipeline with gzip,
> the exit code of the pipeline is 0. I'm not aware of a portable way to
> fix this (named pipes maybe?), but most convenient would be bash's "set
> -o pipefail".

Alas, pipefail is not portable.

> 
> Relevant output from "make V=1 dist":
> 
> tardir=cfengine-3.7.0a1.5ffcc54 && tar --format=ustar -chf - "$tardir" |
> GZIP=--best gzip -c >cfengine-3.7.0a1.5ffcc54.tar.gz

It is portable to do something hairy like:

{ tar ...; echo $? > file; } | gzip ...
inspect file

It is even possible to avoid an intermediate file with even hairier exec
operations to shuffle fds around.

It may be simpler to break things into two steps, with an intermediate
file instead of a pipeline, although I'm not sure it would be efficient.

But you definitely make a point that we should fix things to detect tar
failure.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org