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

[Laszlo Ersek]

On 09/20/21 18:41, Eric Blake wrote:
> 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.
> 

Ah! So "VG" stands for "valgrind", which, in retrospec, probably stands
for "value grind". (Never before have I dissected "valgrind" to
"grinding values"; my non-native English parser doesn't work like that I
guess.)

Thanks!
Laszlo