[R-pkg-devel] Problematicness of Makefile Extensions for CRAN Packages

Hello everybody,

when performing "R CMD check" on my package that contains the sourcecode 
of a third party C++ library, I get a warning telling me to avoid the 
usage of makefile extensions. Before going ahead and trying to temper 
with the library's build-process, I just wanted to ask how severe of a 
problem makefile extensions are. Is there a "gradient" i.e. makefile 
extensions can be tolerated to a certain degree and some are worse than 
others, or are they such a problem with regards to portability that you 
shouldn't use them at all?

With kind regards
Nils L?schow