[Rd] Compiling R-devel on older Linux distributions, e.g. RHEL / CentOS 7

[Gábor Csárdi]

As preparation for the next release, I am trying to compile R devel on
RHEL / CentOS 7, which is still supported by RedHat until 2024 June.
There are two issues.

One is that the libcurl version in CentOS 7 is quite old, 7.29.0, and
R devel now requires 7.32.0, since 83715 about a week ago. This
requirement is here to stay for R 4.3.0, right?

The second is that the recommended packages are now installed with R
CMD INSTALL --use-C17, which fails on CentOS 7 with

begin installing recommended package MASS
* installing *source* package 'MASS' ...
** package 'MASS' successfully unpacked and MD5 sums checked
** using non-staged installation
** libs
Error: C17 standard requested but CC17 is not defined
* removing '/root/R-devel/library/MASS'

CentOS 7 has GCC 4.8.5, which does not have a -std=gnu17 option.
However the commit message of this change in commit 83566 hints that
this requirement might be temporary. Hence my questions.

Is the C17 requirement temporary or it will be a requirement for R 4.3.0?
Should I expect any problems if I remove the --use-C17 flag for
installing the recommended packages?

There are a lot of R users still on RHEL 7, so it would be great to
know what to expect for the next release.

Thank you,
Gábor