[R-pkg-devel] compilation flags WARNING

[Göran Broström]

I am preparing a CRAN release of eha (a trivial change due to a change 
in the survival package), but when checking the build I get:

goran using M6800:~/R$ R CMD check --as-cran eha_2.5.2.tar.gz
...
* checking compilation flags used ... WARNING
Compilation used the following non-portable flag(s):
   ‘-Wdate-time’ ‘-Werror=format-security’ ‘-Wformat’
...

I have never seen this before and I haven't (to my knowledge) set any 
compilation flags. It is my first build and check on a newly upgraded 
ubuntu 18.04 (no issues on 17.10). Should I perhaps ask on r-sig-debian, 
or is that observation irrelevant?

Göran Broström