Re: [PATCH v2 4/6] log: Add _perror() logging function variants

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Jun 18, 2024 at 09:14:25AM +0200, Stefano Brivio wrote:
> In many places, we have direct perror() calls, which completely bypass
> logging functions and log files.
> 
> They are definitely convenient: offer similar convenience with
> _perror() logging variants, so that we can drop those direct perror()
> calls.
> 
> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> ---
>  log.c | 21 +++++++++++++++++++++
>  log.h | 21 +++++++++++++++++----
>  2 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/log.c b/log.c
> index 5853496..9ddc58c 100644
> --- a/log.c
> +++ b/log.c
> @@ -79,6 +79,11 @@ void vlogmsg(int pri, const char *format, va_list ap)
>  	}
>  }
>  
> +/**
> + * logmsg() - vlogmsg() wrapper for variable argument lists
> + * @pri:	Facility and level map, same as priority for vsyslog()
> + * @format:	Message
> + */
>  void logmsg(int pri, const char *format, ...)
>  {
>  	va_list ap;
> @@ -88,6 +93,22 @@ void logmsg(int pri, const char *format, ...)
>  	va_end(ap);
>  }
>  
> +/**
> + * logmsg_perror() - vlogmsg() wrapper with perror()-like functionality
> + * @pri:	Facility and level map, same as priority for vsyslog()
> + * @format:	Message
> + */
> +void logmsg_perror(int pri, const char *format, ...)
> +{
> +	va_list ap;
> +
> +	va_start(ap, format);
> +	vlogmsg(pri, format, ap);
> +	va_end(ap);
> +
> +	logmsg(pri, ": %s", strerror(errno));

The vlogmsg() above could invoke syscalls which clobber errno, so you
need to save it beforehand.

> +}
> +
>  /* Prefixes for log file messages, indexed by priority */
>  const char *logfile_prefix[] = {
>  	NULL, NULL, NULL,	/* Unused: LOG_EMERG, LOG_ALERT, LOG_CRIT */
> diff --git a/log.h b/log.h
> index 1d6dd1d..bdeffde 100644
> --- a/log.h
> +++ b/log.h
> @@ -16,11 +16,18 @@
>  void vlogmsg(int pri, const char *format, va_list ap);
>  void logmsg(int pri, const char *format, ...)
>  	__attribute__((format(printf, 2, 3)));
> +void logmsg_perror(int pri, const char *format, ...)
> +	__attribute__((format(printf, 2, 3)));
> +
> +#define err(...)		logmsg(		LOG_ERR,	__VA_ARGS__)
> +#define warn(...)		logmsg(		LOG_WARNING,	__VA_ARGS__)
> +#define info(...)		logmsg(		LOG_INFO,	__VA_ARGS__)
> +#define debug(...)		logmsg(		LOG_DEBUG,	__VA_ARGS__)
>  
> -#define err(...)	logmsg(LOG_ERR, __VA_ARGS__)
> -#define warn(...)	logmsg(LOG_WARNING, __VA_ARGS__)
> -#define info(...)	logmsg(LOG_INFO, __VA_ARGS__)
> -#define debug(...)	logmsg(LOG_DEBUG, __VA_ARGS__)
> +#define err_perror(...)		logmsg_perror(	LOG_ERR,	__VA_ARGS__)
> +#define warn_perror(...)	logmsg_perror(	LOG_WARNING,	__VA_ARGS__)
> +#define info_perror(...)	logmsg_perror(	LOG_INFO,	__VA_ARGS__)
> +#define debug_perror(...)	logmsg_perror(	LOG_DEBUG,	__VA_ARGS__)
>  
>  #define die(...)							\
>  	do {								\
> @@ -28,6 +35,12 @@ void logmsg(int pri, const char *format, ...)
>  		exit(EXIT_FAILURE);					\
>  	} while (0)
>  
> +#define die_perror(...)							\
> +	do {								\
> +		err_perror(__VA_ARGS__);				\
> +		exit(EXIT_FAILURE);					\
> +	} while (0)
> +
>  extern int log_trace;
>  extern bool log_conf_parsed;
>  extern bool log_daemon_ready;

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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