[Libguestfs] [PATCH nbdinfo v2 3/3] copy: Print debug information with human sizes

[Eric Blake]

On Mon, Sep 20, 2021 at 06:32:29PM +0200, Laszlo Ersek wrote:
> > +++ b/copy/test-verbose.sh
> > @@ -28,11 +28,11 @@ requires nbdkit --version
> >  file=test-verbose.out
> >  cleanup_fn rm -f $file
> >  
> > -$VG nbdcopy -v -- [ nbdkit null ] null: 2>$file
> > +$VG nbdcopy -v -- [ nbdkit memory 1M ] null: 2>$file
> 
> (1) I don't understand this change. Why do we replace "null" with
> "memory 1M"?
> 
> (Side question that I've been meaning to ask: what is this "$VG" magic?)

Answering just the side question:

When LIBNBD_VALGRIND is set to 1 in the environment, then $VG is set
in run.in to an invocation of valgrind, optionally further wrapped by
an invocation of libtool to see through any libtool wrapper script.
Otherwise $VG is empty, and you run the real binary without any outer
wrappers.  It's actually a clever way of checking memory usage issues
during 'make check-valgrind' while probing the real binary rather than
accidentally running valgrind on a shell script.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org