missing format string in applets/usage_pod.c

[Rich Felker]

On Thu, Aug 14, 2014 at 11:58:56PM -0700, Isaac Dunham wrote:
> On Thu, Aug 14, 2014 at 04:15:50PM +0100, Laszlo Papp wrote:
> > On Thu, Aug 14, 2014 at 4:05 PM, Rich Felker <dalias at libc.org> wrote:
> > 
> > > On Thu, Aug 14, 2014 at 03:28:51PM +0100, Laszlo Papp wrote:
> > > > On Thu, Aug 14, 2014 at 2:44 PM, Tanguy Pruvot <tanguy.pruvot at gmail.com>
> > > > wrote:
> > > >
> > > > > its the same with bionic libc (arm)
> > > > >
> > > > > printf("test") is ok but not printf(buf) with char buf[] = "test";
> > > > > printf("%s", buf) is ok
> > > > >
> > > >
> > > > Yeah, I guess it is about personal preference. I personally do not like
> > > the
> > > > extended code just to make some "smart" option silent. IMHO, it makes the
> > > > code needlessly longer by adding another small layer for the content of
> > > the
> > > > variable. If there is no need for formatting, why use printf in the first
> > > > place and not fputs with stdout? IMHO, stdout is nicer than "%s" :-) On
> > > the
> > > > other hand, it is too bad that there is nothing between fputs and puts
> > > > where you do not need to use the file descriptor and you do not get a new
> > > > line either.
> > >
> > > In principle stdout is more expensive than "". stdout is a GOT
> > > reference in PIC, and "" is just PC-relative. For non-PIC it makes no
> > > difference though.
> > >
> > 
> > Then my PC is probably lying since the practice does seem to disagree with
> > you, apparently as well as this post:
> > 
> > http://stackoverflow.com/questions/17238784/c-puts-without-newline#comment24978835_17238840
> > 
> > (and the one below, ok, it is not critical, but it performs better for
> > others, too)
> > 
> > Raw strings are also uglier IMHO than well-defined identifiers, like
> > stdout, but that is personal taste, so I do not mind that one.
>  
> printf() is almost always going to call vfprintf(stdout, fmt, ap);
> I've checked musl, uclibc, glibc, and netbsd; dietlibc is the only
> exception I've found, and it's ugly and does not have locking/retry/...
> newlib calls _vfprintf_r, which is almost the same concept.
> Meanwhile, printf has to do the formatting.
> 
> In other words: 
> Just because printf("%s", string) doesn't name stdout, don't assume that
> it doesn't use a reference to stdout.
> So an ACK for Laszlo Papp's recommendation of fputs().

I was talking about code size overhead, not run time overhead. Of
course there's a reference to stdout in printf. When you reference it
again yourself, that's a second reference. It's not a big deal but
apparently busybox folks care about this kind of micro-optimization...

Rich