Re: [PATCH] iotests: Quote $cmd in _send_qemu_cmd

[Kevin Wolf <kwolf@redhat.com>]

Am 14.12.2020 um 18:58 hat Max Reitz geschrieben:
> With bash 5.1, the output of the following script (which creates an
> array with a single element, then takes a single-element slice from that
> array, and echos the result) changes:
> 
>   a=("double  space")
>   a=${a[@]:0:1}
>   echo "$a"
> 
> from "double space" to "double  space", i.e. all white space is
> preserved as-is.  This is probably what we actually want here (judging
> from the "...to accommodate pathnames with spaces" comment), but before
> 5.1, we have to quote the ${} slice to get the same behavior.
> 
> In any case, without quoting, the reference output of many iotests is
> different between bash 5.1 and pre-5.1, which is not very good.  We
> should fix it by quoting here, and then adjusting all the reference
> output of all iotests using _send_qemu_cmd accordingly.  (The only
> ones we do not need to change are those that do not have multiple
> consecutive whitespaces in their _send_qemu_cmd parameters.)
> 
> Signed-off-by: Max Reitz <mreitz@redhat.com>
> ---
> Alternatively, we could explicitly collapse all whitespace sequences
> into single spaces, but I believe that would defeat the purpose of
> "accomodat[ing] pathnames with spaces".

I agree that quoting is the better alternative.

The whole thing shouldn't be needed if callers propertly quote
filenames. If I understand correctly, these lines just try to merge
back filenames that have been split into multiple words because the
caller wasn't careful. But we can't reliably do that because we don't
know which and how much whitespace was removed.

> I used this script to verify that the git-diff only changes whitespace
> (except for the hunk in common.qemu):
> 
>   https://gist.github.com/XanClic/41cfcc2ac4619421883e8a97790f5c9e

'git diff --word-diff' is good enough for me.

This seems to be based on your branch (312.out doesn't exist yet for
me), so instead of merging, you can just have my:

Reviewed-by: Kevin Wolf <kwolf@redhat.com>