[PATCH] perf debug: List available options when no variable is specified

[PATCH] perf debug: List available options when no variable is specified

[Yang Jihong]

Minor help message improvement for `perf --debug`

Before:

  # perf --debug
  No variable specified for --debug.

   Usage: perf [--version] [--help] [OPTIONS] COMMAND [ARGS]

After:

  # perf --debug
  No variable specified for --debug, available options: verbose,ordered-events,stderr,data-convert,perf-event-open.

Signed-off-by: Yang Jihong <yangjihong1@huawei.com>
---
 tools/perf/perf.c       | 4 +++-
 tools/perf/util/debug.c | 3 +++
 tools/perf/util/debug.h | 1 +
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index d3fc8090413c..0fc4719e6825 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -279,7 +279,9 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			exit(0);
 		} else if (!strcmp(cmd, "--debug")) {
 			if (*argc < 2) {
-				fprintf(stderr, "No variable specified for --debug.\n");
+				fprintf(stderr,
+					"No variable specified for --debug, available options: %s.\n",
+					perf_debug_options_string);
 				usage(perf_usage_string);
 			}
 			if (perf_debug_option((*argv)[1]))
diff --git a/tools/perf/util/debug.c b/tools/perf/util/debug.c
index 88378c4c5dd9..e02f6d97b826 100644
--- a/tools/perf/util/debug.c
+++ b/tools/perf/util/debug.c
@@ -215,6 +215,9 @@ void trace_event(union perf_event *event)
 		     trace_event_printer, event);
 }
 
+const char perf_debug_options_string[] =
+	"verbose,ordered-events,stderr,data-convert,perf-event-open";
+
 static struct sublevel_option debug_opts[] = {
 	{ .name = "verbose",		.value_ptr = &verbose },
 	{ .name = "ordered-events",	.value_ptr = &debug_ordered_events},
diff --git a/tools/perf/util/debug.h b/tools/perf/util/debug.h
index f99468a7f681..b9b4d17a1845 100644
--- a/tools/perf/util/debug.h
+++ b/tools/perf/util/debug.h
@@ -13,6 +13,7 @@ extern int debug_peo_args;
 extern bool quiet, dump_trace;
 extern int debug_ordered_events;
 extern int debug_data_convert;
+extern const char perf_debug_options_string[];
 
 #ifndef pr_fmt
 #define pr_fmt(fmt) fmt
-- 
2.34.1

Re: [PATCH] perf debug: List available options when no variable is specified

[Arnaldo Carvalho de Melo]

Em Tue, Oct 31, 2023 at 08:08:23AM +0000, Yang Jihong escreveu:
> Before:
 
>   # perf --debug
>   No variable specified for --debug.
 
> After:
 
>   # perf --debug
>   No variable specified for --debug, available options: verbose,ordered-events,stderr,data-convert,perf-event-open.

Looks useful, but the implementation can be different to reduce
maintainership costs, see below:

> +++ b/tools/perf/perf.c
> @@ -279,7 +279,9 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
>  		} else if (!strcmp(cmd, "--debug")) {
>  			if (*argc < 2) {
> -				fprintf(stderr, "No variable specified for --debug.\n");
> +				fprintf(stderr,
> +					"No variable specified for --debug, available options: %s.\n",
> +					perf_debug_options_string);
>  				usage(perf_usage_string);

> +++ b/tools/perf/util/debug.c
> @@ -215,6 +215,9 @@ void trace_event(union perf_event *event)
>  		     trace_event_printer, event);
>  }
>  
> +const char perf_debug_options_string[] =
> +	"verbose,ordered-events,stderr,data-convert,perf-event-open";

Instead of adding a new variable that has to be kept in sync with
debug_opts[], you could provide a function that iterates debug_opts,
printing its options names, then use that function on perf.c handle_options.

- Arnaldo

>  static struct sublevel_option debug_opts[] = {
>  	{ .name = "verbose",		.value_ptr = &verbose },
>  	{ .name = "ordered-events",	.value_ptr = &debug_ordered_events},

Re: [PATCH] perf debug: List available options when no variable is specified

[Yang Jihong]

Hello,

On 2023/10/31 23:42, Arnaldo Carvalho de Melo wrote:
> Em Tue, Oct 31, 2023 at 08:08:23AM +0000, Yang Jihong escreveu:
>> Before:
>   
>>    # perf --debug
>>    No variable specified for --debug.
>   
>> After:
>   
>>    # perf --debug
>>    No variable specified for --debug, available options: verbose,ordered-events,stderr,data-convert,perf-event-open.
> 
> Looks useful, but the implementation can be different to reduce
> maintainership costs, see below:
> 
>> +++ b/tools/perf/perf.c
>> @@ -279,7 +279,9 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
>>   		} else if (!strcmp(cmd, "--debug")) {
>>   			if (*argc < 2) {
>> -				fprintf(stderr, "No variable specified for --debug.\n");
>> +				fprintf(stderr,
>> +					"No variable specified for --debug, available options: %s.\n",
>> +					perf_debug_options_string);
>>   				usage(perf_usage_string);
> 
>> +++ b/tools/perf/util/debug.c
>> @@ -215,6 +215,9 @@ void trace_event(union perf_event *event)
>>   		     trace_event_printer, event);
>>   }
>>   
>> +const char perf_debug_options_string[] =
>> +	"verbose,ordered-events,stderr,data-convert,perf-event-open";
> 
> Instead of adding a new variable that has to be kept in sync with
> debug_opts[], you could provide a function that iterates debug_opts,
> printing its options names, then use that function on perf.c handle_options.

Thanks for the advice.
OK, will send a v2 patch according to this scheme.

Thanks,
Yang