[Rd] libcurl support and curlGetHeaders warning message in R CMD check

[Skye Bender-deMoll]

Dear R devel,

Is libcurl support required to run R.devel, or is it optional?

I'm compiling R.devel on an older Debian machine  that only has libcurl 
version 7.21.0

The R news file says

"
Sun, 25 Jan 2015
CHANGES IN R-devel NEW FEATURES

     Optional use of ‘libcurl’ (version 7.28.0 from Oct 2012 or later) 
for Internet access (including on Windows):

...

CHANGES IN R-devel UTILITIES

     ‘R CMD check --as-cran’ checks existence and accessibility of URLs 
in the ‘DESCRIPTION’ file and in the help files.
"

Which seems to suggest libcurl support is optional.   The build process 
seems to correctly detect that I have an old version of libcurl

checking if libcurl version >= 7.28.0... no

 > capabilities('libcurl')
libcurl
   FALSE

But when I try to build any packages with R.devel (for pre-release 
testing) I get lots and lots of Notes/errors like:


Found the following (possibly) invalid URLs:
   URL: http://statnet.org/
     From: DESCRIPTION
     Status: Error
     Message: curlGetHeaders is not supported on this platform

Maybe this url check should first verify that libcurl is available?


If it is the case that libcurl is required for R CMD check --as-cran, 
I'll try to follow up with R debian for how to get appropriate version. 
(seems like libcurl 7.28 is not yet included in a stable Debian release?)

Thanks for your help,

best,
  -skye