Re: [Qemu-devel] [PATCH] tracing.txt: add missing '-' for trace option

[Eric Blake]

On 06/12/2018 10:50 PM, Emilio G. Cota wrote:
> On Tue, Jun 12, 2018 at 23:15:49 -0400, Yaowei Bai wrote:
> > Signed-off-by: Yaowei Bai <address@hidden>
> > ---
> >   docs/devel/tracing.txt | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/docs/devel/tracing.txt b/docs/devel/tracing.txt
> > index 07abbb3..6ab32cc 100644
> > --- a/docs/devel/tracing.txt
> > +++ b/docs/devel/tracing.txt
> > @@ -18,7 +18,7 @@ for debugging, profiling, and observing execution.
> >   
> >   3. Run the virtual machine to produce a trace file:
> >   
> > -    qemu -trace events=/tmp/events ... # your normal QEMU invocation
> > +    qemu --trace events=/tmp/events ... # your normal QEMU invocation
>
> The second dash is not missing; both '-args' and '--args' work.
>
> '-args' seems to be favoured though; see `qemu -h' or `qemu --h' :-)

Actually, we're trying to fix that:
https://wiki.qemu.org/BiteSizedTasks#Consistent_option_usage_in_documentation

The one-vs-two dash usage is only supported in qemu, not in qemu-nbd or 
qemu-img (that is, qemu acts as if it uses getopt_long_only(), while the 
others use getopt_long() - except that we hand-rolled the parser in 
qemu, meaning you might find quirks where it sometimes doesn't even 
match getopt_long_only()).

At any rate, since --trace is an option that is supported across 
multiple binaries, we SHOULD favor the double-dash spelling in our 
documentation, so that you can consistently reuse the same --trace 
invocation without worrying whether the binary parses its arguments with 
getopt_long() (where double is required) or like getopt_long_only() 
(where the double is optional but supported).

So I'm in favor of this patch, although it may need more of a commit 
message summarizing the justification I've just pointed you to.

Reviewed-by: Eric Blake <address@hidden>

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