Re: [PATCH v2 03/11] qemu-option: Remove short form options support

[Markus Armbruster <armbru@redhat.com>]

Fabiano Rosas <farosas@suse.de> writes:

> Option parameters without a value (i.e. key vs. key=val) are
> deprecated. The missing value is currently implied to be either "on"
> or "off" depending on whether the parameter name starts with "no".

Commit ccd3b3b811 (qemu-option: warn for short-form boolean options,
2020-11-09).  Six years of warnings should suffice.

> Remove the implied behavior and start rejecting option parameters
> without values by emitting the error message:
>
>  "Parameter 'foo' without a value."
>
> Two special cases remain:
>
> 1) The 'help' parameter is special and still supported. Keep a
>    positive value attached to it ("on").
>
>    Note that currently there is no validation for the value (if any)
>    attached to the help parameter. help, help=on, help=off, help=foo
>    all result in the help text being emitted. This is not changed by
>    this patch.

Really?

    $ qemu-system-x86_64 -chardev help=foo
    qemu-system-x86_64: -chardev help=foo: Invalid parameter 'help'

> 2) The empty value is allowed if the key is also empty. This can be
>    achieved in the command line by adding commas.
>    E.g.: share=on,, is parsed as:
>      key:"share" value:"on" and
>      key:"" value:"on"

I don't think so:

    $ qemu-system-x86_64 -object memory-backend-ram,id=mem0,share=on,,
    qemu-system-x86_64: -object memory-backend-ram,id=mem0,share=on,,: Parameter 'share' expects 'on' or 'off'

Set a breakpoint on qapi_bool_parse() to see the actual value.  It's
"on,".  In QemuOpts syntax, double comma is an escape, so you can put
comma in values.

> One effect of this change that might not be obvious is that parameter
> combinations of the form:
>
>  id=mem0,share,help
>
> no longer produce the help output. The lack of value for the 'share'
> parameter is reported with precedence. Users will need to either use a
> valid value or omit the parameter entirely:
>
>  id=mem0,share=on,help
>  id=mem0,help

That's unfortunate.

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