ncurses should be built with --enable-termcap to satisfy libreadline dependencies

[akesandgren]

The easyconfig for libreadline says:

\# for the termcap symbols, use EB ncurses
preconfigopts = "env LDFLAGS='-lncurses'"

But the easybuilt ncurses does not contain, for instance, this termcap symbol, tgetflag, which libreadline uses.

ncurses needs to be built with --enable-termcap to contain the required symbols.
And to work for libreadline, --with-termlib can not be used (like it currently is for ncurses-6.0.eb) becuse then those symbols end up in libtinfo

[boegel]

@wpoely86 I think you've looked into this before, thoughts?

I'm not sure if switching to not using --with-termlib is an option now though, unless that's a pure bug fix and doesn't cause any other fallout...

[wpoely86]

Weird, our ncurses do have this symbol. I checked and we don't use libtinfo anywhere in ncurses (or libreadline).

You seem to have an interesting build system @akesandgren What OS are you using to trigger this?

[geimer]

Maybe kind of related: Even though ncurses is listed as a build dependency for LLVM, it seems to pick up libtinfo.so from the system, as --with-termlib is not given for the non-dummy ncurses builds. So, if --with-termlib can't be used for libreadline, but may be needed for LLVM, we are in a catch-22 situation, no?

[wpoely86]

Not really I think.
We need to enable --with-termlib but that means we can drop -lncurses and replace it by -ltinfo in a lot of cases (including libreadline). At least, that's how I understand it.

[akesandgren]

@wpoely86 Ubuntu xenial, I had no changes to the ncurses easyconfigs at the time.

[boegel]

@akesandgren Is this still relevant after the changes in #5067 and #5074?

[akesandgren]

Hopefully not, but I don't remember what chain was actually hit by the problem.
Let's close this one as not needed due to the above and go on with life.