Re: CVS commit: src/lib/libwrap

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Thu, 10 Jan 2019 20:21:52 -0500
    From:        christos%zoulas.com@localhost (Christos Zoulas)
    Message-ID:  <20190111012152.CC59917FDA1%rebar.astron.com@localhost>

  | I understand, this is why I grepped the source for %m and saw that there
  | was no use other than " %m\0". 

The point was most that libwrap is a public library, and in its tcpd.h
it declares tcpd_warn() as a public function, and notes it as __syslog_like
which means that it handles %m.

Anyone, anywhere (who links against libwrap) can call that function.

That's why I susggested that perhaps what we should do is document
the issue, so that if there is anyone who decides that they need to
include a message that has something like "%d%%mbufs"
that they can expect something quite different than they hoped.
Similarly, if they were even just to use (for some obscure reason)
two %m conversions in one message.

I am not sure where that doc ought be put however, as tcpd_warn
doesn't seem to be documented anywhere (than in tcpd.h).

[This also applies to tcpd_jump() of course, but that one is kind
of hard to imagine anyone wanting to use.]

  | Yes, that is something I wished for many times. But then there are
  | trade-offs (such as compile time checking) and other safety guarantees.

Of course ... perhaps we could make it so that the act of specifying a
new format conversion creates a new printf clone function (which gcc
would then know nothing about ...) which also solves the "lifetime of
the conversion routine" issue (the function which would be provided
to handle the added format would need to exist just as long as the
returned function pointer is kept alive).

Then only calls which need to use the added format would use the
created function, all others would just use the existing ones, with all
the gcc validity checking, and only the others would use the new
one and miss out ... which is certainly no worse than calls which
process the format string, modifying it to insert the data wanted by
the new conversion, then passing the newly constructed format to
printf.

kre