Re: [PATCH 2/5] dmesg: error out on unknown loglevels

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Jun 13, 2023 at 08:34:39AM +0200, Marco Felsch wrote:
> Hi Sascha,
> 
> On 23-06-12, Sascha Hauer wrote:
> > The user deserves an error when an unknown loglevel is given, so
> > print an error instead of silently ignoring unknown loglevels.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  commands/dmesg.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/commands/dmesg.c b/commands/dmesg.c
> > index 339910bb76..2a36710b98 100644
> > --- a/commands/dmesg.c
> > +++ b/commands/dmesg.c
> > @@ -32,6 +32,8 @@ static int str_to_loglevel(const char *str)
> >  	if (!strcmp(str, "emerg"))
> >  		return MSG_EMERG;
> >  
> > +	printf("dmesg: unknown loglevel %s\n", str);
> > +
> >  	return -EINVAL;
> >  }
> >  
> > @@ -51,6 +53,8 @@ static unsigned dmesg_get_levels(const char *__args)
> >  		level = str_to_loglevel(str);
> >  		if (level >= 0)
> >  			flags |= BIT(level);
> > +		else
> > +			return 0;
> 
> This is more explicit but wouldn't be required since we initialized
> 'flags = 0'.

It is required as flags might be != 0 already and we want to return 0
in error case. Nevertheless this needs fixing as this return looses
memory allocated with xstrdup above.

> 
> >  	}
> >  
> >  	free(args);
> > @@ -81,7 +85,7 @@ static int do_dmesg(int argc, char *argv[])
> >  		case 'l':
> >  			levels = dmesg_get_levels(optarg);
> >  			if (!levels)
> > -				return COMMAND_ERROR_USAGE;
> > +				return COMMAND_ERROR;
> 
> Out of curiosity what's the difference between COMMAND_ERROR and
> COMMAND_ERROR_USAGE?

When a command returns with COMMAND_ERROR_USAGE then the usage
for the command is printed. COMMAND_ERROR just returns an error
without printing the commands usage.

When a command prints a meaningful error message then I often
find it confusing when the usage is printed, because the error
is often buried in the long help text.

Sascha

---------------------------8<------------------------------

>From adadd6c0fcfd6b11076e0110497dd7ecdb44f99c Mon Sep 17 00:00:00 2001
From: Sascha Hauer <s.hauer@pengutronix.de>
Date: Mon, 12 Jun 2023 14:12:11 +0200
Subject: [PATCH] dmesg: error out on unknown loglevels

The user deserves an error when an unknown loglevel is given, so
print an error instead of silently ignoring unknown loglevels.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 commands/dmesg.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/commands/dmesg.c b/commands/dmesg.c
index 339910bb76..0d46353fb5 100644
--- a/commands/dmesg.c
+++ b/commands/dmesg.c
@@ -32,6 +32,8 @@ static int str_to_loglevel(const char *str)
 	if (!strcmp(str, "emerg"))
 		return MSG_EMERG;
 
+	printf("dmesg: unknown loglevel %s\n", str);
+
 	return -EINVAL;
 }
 
@@ -49,8 +51,12 @@ static unsigned dmesg_get_levels(const char *__args)
 			break;
 
 		level = str_to_loglevel(str);
-		if (level >= 0)
-			flags |= BIT(level);
+		if (level < 0) {
+			flags = 0;
+			break;
+		}
+
+		flags |= BIT(level);
 	}
 
 	free(args);
@@ -81,7 +87,7 @@ static int do_dmesg(int argc, char *argv[])
 		case 'l':
 			levels = dmesg_get_levels(optarg);
 			if (!levels)
-				return COMMAND_ERROR_USAGE;
+				return COMMAND_ERROR;
 			break;
 		case 'r':
 			flags |= BAREBOX_LOG_PRINT_RAW | BAREBOX_LOG_PRINT_TIME;
-- 
2.39.2

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