Re: [GIT PULL 21/50] qemu-io: propagate errors through Error API instead of printf

[Kevin Wolf <kwolf@redhat.com>]

Am 28.08.2026 um 22:42 hat Marc-André Lureau geschrieben:
> Convert the qemu-io command infrastructure to use QEMU's Error API
> (Error **errp) for error propagation instead of printing directly to
> stdout/stderr via printf/fprintf.
> 
> The cfunc_t typedef, all ~35 command functions, the dispatcher chain
> (command/init_check_command/qemuio_command), and helper functions
> (parse_pattern, create_iovec, qemu_io_alloc_from_file) all gain an
> Error **errp parameter. Async completion callbacks (aio_read_done,
> aio_write_done, aio_discard_done) use error_report() since they have
> no Error path back to the caller.
> 
> Update tests:
> - error_report_err() prepends qemu-io: prefix
> - copy-before-write: check the HMP return value, rather than stdio
> - other tests: update to check JSON {"return": "Error: error text"}
> 
> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Message-ID: <20260828-qemu-no-hmp-v5-21-9227de146347@redhat.com>

This was not a great change, it results in a mess for qemu-io output.

When used from HMP, success output still ends up on stdout, but (some)
errors go to the monitor instead now. Some commands may even get their
output split across both stdout and the monitor. The old experience
wasn't great (everything should have gone to the monitor instead of
having everything in the terminal), but the new one is terrible.

Please fix the inconsistency or revert.

> diff --git a/tests/qemu-iotests/004.out b/tests/qemu-iotests/004.out
> index fb8593289f51..37da6024809f 100644
> --- a/tests/qemu-iotests/004.out
> +++ b/tests/qemu-iotests/004.out
> @@ -6,36 +6,36 @@ wrote 1048576/1048576 bytes at offset 133169152
>  1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
>  
>  write into image boundary
> -write failed: Input/output error
> +qemu-io: write failed: Input/output error
>  [...]

Instead changing the output of all test outputs to include an
unnecessary and inconsistently applied "qemu-io" prefix, it would have
been better to disable the prefix after command line parsing.

qemu-io is still primarily an interactive program, and constantly
printing the name of the program you're interacting with has little
value.

Kevin