Re: [PATCH v5 1/2] add-patch: do not show UI messages on stderr

From: Rubén Justo <rjusto@gmail.com>
Date: Apr 30, 2024, 16:35 UTC
Message-ID: <90464326-0d0a-4cc6-84cd-eb1e5489a91a@gmail.com>
In-Reply-To: <20240430105256.GH1279403@coredump.intra.peff.net>

On Tue, Apr 30, 2024 at 06:52:56AM -0400, Jeff King wrote:

Show 26 quoted lines

> On Mon, Apr 29, 2024 at 12:24:46PM -0700, Junio C Hamano wrote:
> 
> > Rubén Justo <rjusto@gmail.com> writes:
> > 
> > > diff --git a/add-patch.c b/add-patch.c
> > > index 0997d4af73..fc0eed4fd4 100644
> > > --- a/add-patch.c
> > > +++ b/add-patch.c
> > > @@ -293,10 +293,9 @@ static void err(struct add_p_state *s, const char *fmt, ...)
> > >  	va_list args;
> > >  
> > >  	va_start(args, fmt);
> > > -	fputs(s->s.error_color, stderr);
> > > -	vfprintf(stderr, fmt, args);
> > > -	fputs(s->s.reset_color, stderr);
> > > -	fputc('\n', stderr);
> > > +	fputs(s->s.error_color, stdout);
> > > +	vprintf(fmt, args);
> > > +	puts(s->s.reset_color);
> > 
> > I like the attention of the detail here ;-).
> 
> Indeed. I had to read this several times to wonder why it was not a
> mistake to leave the first fputs() but use vprintf() and puts() for the
> other two (for those just reading, the answer is that puts() prints an
> extra newline, so we can only use it at the end).

I did not know the details (or had happily forgotten them) but Junio ignoring my comments in [1] intrigued me :-). A simple test would have been quick, but "man puts" was quicker; my comments were not correct.

Just to be clear, and to extend your comment, in case any reader is interested, this:

	vfprintf(stdout, fmt, args);

can be written as follows:

	vprintf(fmt, args);

And this:

	fputs(s->s.reset_color, stdout);
	fputc('\n', stdout);

can be shortened to:

	puts(s->s.reset_color);

The difference in vfprintf and vprintf is quite obvious IMHO, but not so obvious with puts. The documentation says:

  SYNOPSIS

       int puts(const char *s);

  DESCRIPTION

       puts() writes the string s and a trailing newline to stdout.

  [1] - https://lore.kernel.org/git/4e2bc660-ee33-4641-aca5-783d0cefcd23@gmail.com/T/#m644a682364212729a2b21c052ef744039c26f972