[R-pkg-devel] Conditional linking in Makevars

[David Cortes]

I am having issues with undefined compiler symbols in a package with C
code that I recently updated:
https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-debian-clang/poismf-00install.html
The issue seems to be connected with usage of OpenMP, and happens only
when compiling with clang:
“Error: package or namespace load failed for 'poismf' in dyn.load(file,
DLLpath = DLLpath, ...):
 unable to load shared object '/home/hornik/tmp/R.check/r-devel-
clang/Work/build/Packages/00LOCK-poismf/00new/poismf/libs/poismf.so':
  /home/hornik/tmp/R.check/r-devel-clang/Work/build/Packages/00LOCK-
poismf/00new/poismf/libs/poismf.so: undefined symbol:
__atomic_compare_exchange”


Prof. Ripley left the following comment:
“I don't know what makes your use of OpenMP uniquely different but
when 
using clang you need to include -latomic in the link (where it exists, 
as it does on Linux and probably on FreeBSD).”

I am wondering if it is somehow possible to add conditional link
arguments in a Makevars file depending on the user’s operating system,
or if not possible, whether it would somehow hurt in windows/mac
installations to add a raw -latomic in there.


Best regards,
David Cortes