Re: possible getopt stderr output changes

[Rich Felker <dalias@libc.org>]

On Wed, Dec 10, 2014 at 07:10:32PM -0500, Rich Felker wrote:
> The current getopt code uses some ugly write() sequences to generate
> its output to stderr, and fails to support message translation. The
> latter was an oversight when locale/translation support was added and
> should absolutely be fixed. I'm not sure whether we should leave the
> code using write() though or switch to fprintf.

It's been pointed out on irc that POSIX requires ferror(stderr) to be
set if writing the message fails. However fwrite could still be used
instead of fprintf. If we need to use stdio at all, however, I'd lean
towards wanting to make the whole write atomic (i.e. hold the lock for
the whole time) which is more of a pain without fprintf. So basically
we're looking at:

fprintf:
PROS: smaller and simpler code in getopt.c, only one syscall
CONS: additional ~6.5k of additional code pulled in for static

fwrite:
PROS: minimal static linking deps
CONS: need to use flockfile (or implementation internals) for
atomicity if desired, and multiple writes (so no atomicity on the fd)

Rich