[Libguestfs] [PATCH nbdkit 1/2] tests: Remove QEMU_IO / HAVE_QEMU_IO.

[Eric Blake]

On 03/07/2018 09:39 AM, Richard W.M. Jones wrote:

>> Needs rebasing now that the test no longer relies on file-data.
>> Also, I still appreciate being able to override $QEMU_IO from the
>> command line (to point to an alternative version on the fly), so
>> even though I agree with your Makefile changes, I disagree with
>> dropping the defaulting of QEMU_IO to qemu-io,
> 
> Does setting $PATH not work for this purpose?
> 
> Rich.
> 
>>>   # Populate file, and sanity check that qemu-io can issue parallel requests
>>>   printf '%1024s' . > test-parallel-file.data
>>> -$QEMU_IO -f raw -c "aio_write -P 1 0 512" -c "aio_write -P 2 512 512" \
>>> +qemu-io -f raw -c "aio_write -P 1 0 512" -c "aio_write -P 2 512 512" \
>>
>> as well as disagree with hard-coding only the first qemu-io in $PATH
>> here, instead of allowing a command-line override.

Well, using PATH overrides might work, but it can also be more verbose. 
It's also trickier: if you have two binaries residing in a single 
directory - say qemu-io and qemu-img - but only want the override to 
apply for just one of those binaries, then a direct QEMU_IO override 
would do it at once, but a PATH override would require creating a 
temporary directory, adding a symlink in the temp directory to pick up 
the one binary that will be used as an override, then pointing PATH to 
pick up the temp directory first.

But since you are right that a PATH override is always possible, even if 
more verbose, I won't insist on a QEMU_IO override as it is merely 
syntactic sugar.

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