[R-pkg-devel] Checking for C++11

[Marvin Wright]

Dear all, 

I would like to check for C++11 support in a package. The package requires gcc >= 4.7 or clang >= 3.0. Windows is handled differently in Makevars.win. I tried two approaches in Makevars so far, but both give warnings in CRAN checks. 

Approach 1: 
## Check for gcc >= 4.7
ifeq ($(shell basename $(CC)),gcc)
GCC_VER := $(shell gcc -dumpversion)
GCC_MAJOR := $(shell gcc -dumpversion | cut -f1-2 -d.)

GCC_OK := $(shell echo $(GCC_MAJOR) \>= 4.7 | bc )
ifneq ($(GCC_OK),1)
  $(error Error: gcc >= 4.7 required, version $(GCC_VER) installed. Please update gcc.)
endif
endif

Works quite well but a warning in check —as-cran: 
> Found the following file(s) containing GNU extensions:
> src/Makevars
> Portable Makefiles do not use GNU extensions such as +=, :=, $(shell),
> $(wildcard), ifeq ... endif. See section ‘Writing portable packages’ in
> the ‘Writing R Extensions’ manual.


Approach 2: 
Use std=c++11 flag instead of CXX_STD = CXX11, which should work on gcc >=4.7 and throw an error on earlier versions. 

This time in check —as-cran: 
> Non-portable flags in variable 'PKG_CPPFLAGS':
> -std=c++11

Any other ideas how to check? Or is one of the versions above OK on CRAN? 

Thanks, 

Marvin