Re: [PATCH] perf stat: reject --field-separator and --json-output combination

[Namhyung Kim <namhyung@kernel.org>]

Hello,

On Sun, Jul 05, 2026 at 02:58:40AM +0200, Ivan Lazaric wrote:
> Specifying --field-separator option is stating you want CSV output.
> Passing both --field-separator and --json-output is then stating
> you want output to be in CSV and JSON format at same time.
> 
> Currently this combination is not rejected, and the outcome
> is a malformed combination of CSV and JSON output.
> This is because of inconsistencies in various printing functions,
> some of them have if-else chains that start with
> "Should I print JSON?", and some start with "Should I print CSV?".
> 
> Example of current output:
> $ tools/perf/perf stat -x , -j -e cpu-migrations true
> {"counter-value" : "0.000000", "unit" : "", "event" : "cpu-migrations", "event-runtime" : 474817, "pcnt-running" : 100.00,,
> 
> Instead reject the option combination,
> with a helpful error message and non-zero exit code.
> 
> Example of new output:
> $ tools/perf/perf stat -x , -j true
> cannot use both --field-separator and --json-output
> 
>  Usage: perf stat [<options>] [<command>]
> 
>     -x, --field-separator <separator>
>                           print counts with custom separator
>     -j, --json-output     print counts in JSON format
> 
> Signed-off-by: Ivan Lazaric <ivan.lazaric1@gmail.com>

Thanks for the patch, but it doesn't apply cleanly.  Can you please
rebase it on to the latest perf-tools-next branch?

Thanks,
Namhyung