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

[Stefan Hajnoczi]

On Wed, Jun 13, 2018 at 10:15:10AM -0400, Yaowei Bai wrote:
> On Wed, Jun 13, 2018 at 06:27:49AM -0500, Eric Blake wrote:
> > 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
> 
> Yes, this patch is inspired by this situation when translating DPRINT into
> trace for a new qemu utility (much like qemu-nbd) following 
> docs/devel/tracing.txt.
> The utility complains it don't support -trace option. So i sent this
> patch after confirming this with qemu-nbd,qemu-io utilities.
> 
> > 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.
> 
> Thanks for your nice explaination. If this patch could be merged i will
> send V2 with a commit message.

Please update the remaining occurrences of the -trace option syntax in
v2:

  $ git grep -- -trace docs/devel/tracing.txt

Stefan

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