[R-sig-Debian] Configure error: checking if libcurl supports https... no

[Rolf Turner]

I asked this question a short while ago on the R-help list, and
received an off-list reply from Ivan Krylov, suggesting that it would
be better to ask on r-sig-debian.  So here goes:  to set the context,
I'm running Ubuntu 20.04, with a Mate 1.24.0 desktop.

The question is long and complicated; you will need a great deal of
patience to plough through it.  (Sorry 'bout that!)

I'm getting results from a package (written by my very good self) which
differ (rather mysteriously) from results that I got a few weeks ago,
and the only thing that I can think of that's changed is the version of
R (from 4.1.0 to 4.4.1).

So I wanted to install 4.1.0 and play around with that, to see if that
is indeed the explanation.  (If that is so, a whole new set of
questions would be raised, but let's not go there, for the moment.)  I
downloaded the tarball and set about installing 4.1.0 from source.  But
the configure step threw an error, as given in the subject line of
this message.  The error went on:

> configure: error: libcurl >= 7.28.0 library and headers are required
> with support for https  

A bit of web searching turned up the advice to re-install curl
using

    sudo apt-get install curl

but when I did that I was informed that:

> curl is already the newest version (7.68.0-1ubuntu2.6).

Prof. Krylov suggested in his off-list email that I should do:

    sudo apt install libcurl-dev

So I did that (effectively; but see below) and what I did seemed to run
without (too much) complaint, but the configure error persisted.

When I tried "sudo apt install libcurl-dev" I got a message to the
effect that "libcurl-dev" was ambiguous.  Explicitly:

> Package libcurl-dev is a virtual package provided by:
>   libcurl4-openssl-dev 7.68.0-1ubuntu2.6
>   libcurl4-nss-dev 7.68.0-1ubuntu2.6
>   libcurl4-gnutls-dev 7.68.0-1ubuntu2.6
> You should explicitly select one to install.
> 

Hmmm.  Which one?  No idea, really, but the config.log file was
full of stuff relating to errors from "openssl.c" (*way* beyond my pay
grade!!!) so I thought I'd try the first one.

As indicated above,

    sudo apt-get install libcurl4-openssl-dev

seemed to run without complaint, although it said

> The following packages will be REMOVED
>   libcurl4-gnutls-dev

which made me think that maybe I should have used "libcurl4-gnutls-dev".
But I carried on, and the command ran (without --- further ---
complaint).  However, as I said, the configuration error persisted.

So I then tried:

   sudo apt remove libcurl4-openssl-dev

and got a whole lot of ominous warnings, starting:

> dpkg: libcurl4-openssl-dev:amd64: dependency problems, but removing
> anyway as you requested:
>  libdap-dev:amd64 depends on libcurl4-gnutls-dev | libcurl-dev;
> however: Package libcurl4-gnutls-dev is not installed.
>   Package libcurl-dev is not installed.
>   Package libcurl4-openssl-dev:amd64 which provides libcurl-dev is to
> be removed.

(There was more ....)

Having done that I crossed my fingers and tried:

    sudo apt-get install libcurl4-gnutls-dev

and got

> libcurl4-gnutls-dev is already the newest version (7.68.0-1ubuntu2.6).
> libcurl4-gnutls-dev set to manually installed.

So I then tried *removing* libcurl4-gnutls-dev (that seemed to work!)
and then re-installing it.  *That* seemed to work too, and there were
no more messages about "manually installed".

But the configure error *still* persisted!!!

I am now out of ideas, at my wits' end, at the end of my tether, and a
few other things.

Can anyone suggest anything else that I might try?  If so, can I
very humbly exhort you to please (*please* *PLEASE*) present it in very
simple terms if you can. (I am a Bear of Very Little Brain, and long
words bother me.) A step-by-step recipe would be appreciated.

As you can see from this long-winded question, I really have no idea at
all what I am doing, and am basically issuing commands by rote,
hammering and hoping.  (With the hopes always being dashed. :-( )
Consequently any advice, that presupposes that I have *insight* into
the processes that I am invoking, is unlikely to be of any use to me.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276