Re: [PATCH v2] perf stat: reject --field-separator and --json-output combination

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Jul 08, 2026 at 01:36:55PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [Low] Missing explicit inclusion of `<stdio.h>` for standard I/O functions and types.
> --
> 
> --- Patch [1]: [PATCH v2] perf stat: reject --field-separator and --json-output combination ---
> commit 14ca4ce3700a93ed48a3336a633292f7e45ae462
> Author: Ivan Lazaric <ivan.lazaric1@gmail.com>
> 
> perf stat: reject --field-separator and --json-output combination
> 
> This patch explicitly rejects using both the --field-separator and
> --json-output options in perf stat. It adds a check to output an error
> message and exit cleanly, preventing malformed mixed formats.
> 
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index a04466ea3b0a0..6ec82752d71c6 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -2643,6 +2643,13 @@ int cmd_stat(int argc, const char **argv)
> >  
> >  	stat_config.aggr_mode = opt_aggr_mode_to_aggr_mode(&opt_mode);
> >  
> > +	if (stat_config.csv_sep && stat_config.json_output) {
> > +		fprintf(stderr, "cannot use both --field-separator and --json-output\n");
>                 ^^^^^^^
> 
> [Severity: Low]
> Could this cause a build failure when compiling perf with musl libc?
> 
> While glibc often implicitly includes standard headers, musl has stricter
> header separation.
> 
> Since this code introduces a new call to fprintf and uses stderr, does
> builtin-stat.c need an explicit #include <stdio.h> in its global includes
> block to guarantee musl compatibility?

It should be fine as it's used in other places already.

Thanks,
Namhyung

> 
> > +		parse_options_usage(stat_usage, stat_options, "x", 1);
> > +		parse_options_usage(NULL, stat_options, "j", 1);
> > +		goto out;
> > +	}
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260708131359.71732-3-ivan.lazaric1@gmail.com?part=1