Re: ANN: NetworkManager (0.9.10-rc1) released

On Thu, 26 Jun 2014 12:27:14 -0500
Robby Workman <robby rlworkman net> wrote:

On Thu, 26 Jun 2014 10:16:41 -0500
Dan Williams <dcbw redhat com> wrote:

On Thu, 2014-06-26 at 01:19 -0500, Robby Workman wrote:
On Thu, 26 Jun 2014 07:55:58 +0200
Vincent Bernat <bernat luffy cx> wrote:

 ❦ 25 juin 2014 21:36 -0500, Robby Workman
<robby rlworkman net> :

Okay, looks like that's ncurses, so let's link ncurses too:

  [rworkman liberty NetworkManager-]$ gcc -o testrl
-lreadline -lncurses testrl.c [rworkman liberty
NetworkManager-]$ strings testrl | grep readline readline

Now, here's where I'm unclear.  If I add LDFLAGS="-lnurses" to
the configure environment, the test passes and the complete
build occurs successfully. What's unclear is *why* that's
needed -- is this an omission in the NM sources (isn't nmtui a
curses client and thus ncurses should be linked?) or is
something different about how we (Slackware) build readline?

GNU readline requires linking to ncurses as well to get termcap
symbols. Here is an autoconf recipe for that:

If I'm reading that correctly, that snippet above tries to link
in curses if it encounters failure, so perhaps NM should use it?
Maybe not though - there's at least one other project (nftables)
where I've encountered the same problem.

While digging around a bit after sending this, I found that we add
"--with-curses" to the readline configure to use it instead of 
libtermcap, so it's *supposed* to be linked in already and this 
would not be a problem.  However, for whatever reason (it's not
clear whether it's intentional or not), the upstream sources don't
use TERMCAP_LIBS (set to "-lcurses" per the configure flag) when
building the shared library.  It appears that at least one distro
solves that by running 'make SHLIB_LIBS="-lcurses"' when building,
but I don't see where Fedora did that, so it's not clear at all 
how they link curses (or even if they do, when means I wonder how
the configure test in OP works there). 

Assuming this is indeed a problem, it's been in Slackware for
years without causing any actual issues - the readline library
from 13.37 (released in April 2011) doesn't link ncurses either,
so I'm not convinced that we're doing anything wrong (but I'm
open to argument).

What does 'ldd' on your return?  Mine has: =>  (0x00007fff191fe000) => /lib64/ (0x0000003473400000) => /lib64/ (0x000000345ac00000)
    /lib64/ (0x000000345a800000)

so at least the dynamic linker knows that libtinfo (provided by
ncurses) is required here, and should load that in for the configure
test program.

# ldd /usr/lib64/ (0x00007ffff43ff000) => /lib64/ (0x00007ffda6b37000)
      /lib64/ (0x00007ffda7179000)

I don't have any links to support this, but in talking with a couple
of folks who've "been around a while," it seems that the lack of
direct linking is intentional on the part of upstream readlinke --
this allows the specific apps to use whichever (termcap / ncurses) is
appropriate for them.  The autoconf stuff linked earlier seems to
somewhat support that, but again, I don't have a definitive answer on

...and comment #1 seems to support that (but apparently the official
RH position changed since then):

Also, the INSTALL file in readline sources says this (no idea how I 
originally missed it): 

    This tells readline that it can find the termcap library functions
    (tgetent, et al.) in the curses library, rather than a separate
    termcap library.  Readline uses the termcap functions, but does not
    link with the termcap or curses library itself, allowing applications
    which link with readline the to choose an appropriate library.
    This option tells readline to link the example programs with the
    curses library rather than libtermcap.


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