[R] Set compilation standard to C++17 on Windows, remove it on Unix (Closes #3407)

[eddelbuettel]

This PR suggests to increase the compilation standard from C++14 to C++17 to preempt a nag from CRAN.

With the suggested change, and on a (very recent, just updated) r-devel we now get a new line (that I just tweeted about too) that is actually just a comment after an OK instead of the nag I reported in #3407.

The full log with this change (as well as with #3405 addressing my #3406) we get the (good, passing) check below. Note that for that check I also increased the version number locally to make it distinct, this is not part of the PR.

edd@rob:/tmp/rcpp$ rdcc.sh mlpack_4.0.1.1.tar.gz                                                          
* using log directory ‘/tmp/mlpack.Rcheck’
* using R Under development (unstable) (2023-02-09 r83797)
* using platform: x86_64-pc-linux-gnu (64-bit)
* R was compiled by          
    gcc (Ubuntu 12.2.0-3ubuntu1) 12.2.0
    GNU Fortran (Ubuntu 12.2.0-3ubuntu1) 12.2.0
* running under: Ubuntu 22.10                      
* using session charset: UTF-8                     
* using option ‘--as-cran’          
* checking for file ‘mlpack/DESCRIPTION’ ... OK
* this is package ‘mlpack’ version ‘4.0.1.1’                                                             
* package encoding: UTF-8                      
* checking CRAN incoming feasibility ... [5s/11s] Note_to_CRAN_maintainers
Maintainer: ‘Ryan Curtin <ryan@ratml.org>’ 
* checking package namespace information ... OK
* checking package dependencies ... OK           
* checking if this is a source package ... OK                                                            
* checking if there is a namespace ... OK       
* checking for executable files ... OK                                                                   
* checking for hidden files and directories ... OK 
* checking for portable file names ... OK
* checking for sufficient/correct file permissions ... OK
* checking whether package ‘mlpack’ can be installed ... [534s/414s] OK
* used C++ compiler: ‘g++ (Ubuntu 12.2.0-3ubuntu1) 12.2.0’
* checking C++ specification ... OK
  Not all R platforms support C++17
* checking installed package size ... NOTE
  installed size is 18.7Mb             
  sub-directories of 1Mb or more:       
    libs  18.3Mb                                                                                         
* checking package directory ... OK                 
* checking for future file timestamps ... OK
* checking DESCRIPTION meta-information ... OK
* checking top-level files ... OK
* checking for left-over files ... OK
* checking index information ... OK
* checking package subdirectories ... OK
* checking R files for non-ASCII characters ... OK
* checking R files for syntax errors ... OK
* checking whether the package can be loaded ... OK
* checking whether the package can be loaded with stated dependencies ... OK
* checking whether the package can be unloaded cleanly ... OK
* checking whether the namespace can be loaded with stated dependencies ... OK
* checking whether the namespace can be unloaded cleanly ... OK
* checking loading without being on the library search path ... OK
* checking use of S3 registration ... OK
* checking dependencies in R code ... OK
* checking S3 generic/method consistency ... OK
* checking replacement functions ... OK
* checking foreign function calls ... OK
* checking R code for possible problems ... OK
* checking Rd files ... OK
* checking Rd metadata ... OK
* checking Rd line widths ... OK
* checking Rd cross-references ... OK
* checking for missing documentation entries ... OK
* checking for code/documentation mismatches ... OK
* checking Rd \usage sections ... OK
* checking Rd contents ... OK
* checking for unstated dependencies in examples ... OK
* checking line endings in shell scripts ... OK
* checking line endings in C/C++/Fortran sources/headers ... OK
* checking line endings in Makefiles ... OK
* checking compilation flags in Makevars ... OK
* checking for GNU extensions in Makefiles ... OK
* checking for portable use of $(BLAS_LIBS) and $(LAPACK_LIBS) ... OK
* checking use of PKG_*FLAGS in Makefiles ... OK
* checking use of SHLIB_OPENMP_*FLAGS in Makefiles ... OK
* checking pragmas in C/C++ headers and code ... OK
* checking compilation flags used ... OK
* checking compiled code ... OK
* checking examples ... OK
* checking for unstated dependencies in ‘tests’ ... OK
* checking tests ...
  Running ‘testthat.R’
 OK
* checking PDF version of manual ... OK
* checking HTML version of manual ... OK
* checking for non-standard things in the check directory ... OK
* checking for detritus in the temp directory ... OK
* DONE

Status: 1 NOTE
See
  ‘/tmp/mlpack.Rcheck/00check.log’
for details.

$ 

[eddelbuettel]

Further revision is to keep the compilation standard setting for Windows, but roll it to C++17. We can remove it once R upgraded.

There was a recently found issue that Windows did not properly progagate the default compilation standard to C++14 so by removing it we likely fell back to C++11 which is why Windows failed.

[rcurtin]

Thanks---I appreciate this! Always good to stay ahead of the CRAN nags. 👍

[mlpack-bot]

Second approval provided automatically after 24 hours. 👍