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

[Stefano Brivio <sbrivio@redhat.com>]

On Wed, 19 Jun 2024 12:21:56 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> 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.

Oops, nice catch.

-- 
Stefano