[Bug 1859989] Re: qemu-img has broken output with large snapshot names

From: Max Reitz <1859989@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1859989] Re: qemu-img has broken output with large snapshot names
Date: Fri, 17 Jan 2020 10:13:35 -0000	[thread overview]
Message-ID: <157925601569.23128.14572633577549563237.malone@gac.canonical.com> (raw)
In-Reply-To: 157918316689.4864.12553262908100217782.malonedeb@wampee.canonical.com

I’ve just seen that launchpad collapses the spaces in the snapshot...
All I can say is that diff tells me the output from 2.12.0 and 4.1.1 is
exactly the same, with only one difference: 2.12.0 prints the VM SIZE as
“0” (without a unit), whereas 4.1.1 prints “0 B”.

But now I just realized you probably mean that there is no space between
the snapshot name and the VM state size in your example.  OK, I thought
you meant the fact that the headers are not aligned to the table body
columns.

That seems to be because the size is printed in a 7-wide field, which
isn’t sufficient for three-digit sizes with unit prefixes; so “747 MiB”
is not prefixed by a space.  I think de38b5005e9 is to blame which which
(from what I can tell) effectively changed the output from using SI
prefixes to IEC prefixes (which requires one more character), adds a
space before and a “B” after the prefix (another two additional
characters), and by always printing three digits, which may require a
decimal point (so another character).  But it didn’t grow the field
width.  So I think we should do that.

Max

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https://bugs.launchpad.net/bugs/1859989

Title:
  qemu-img has broken output with large snapshot names

Status in QEMU:
  New

Bug description:
  On Qemu 4.1.1 the output of snapshots breaks if the chosen state name
  is too long:

  ```
  # qemu-img snapshot -l /mnt/local/some_image.qcow2
  Snapshot list:
  ID        TAG                 VM SIZE                DATE       VM CLOCK
  1         online_provider_with_dhcp747 MiB 2020-01-15 12:05:01   00:00:45.873
  ```

  Prior to 4.1.1 this used to work with extra tabs for the VM SIZE
  values. The collision is also disabling us from using a regex on top
  of this output to detect the snapshot.

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