"C++11 compiler required; enable C++11 mode in your compiler, or use an earlier version of Armadillo" Error in Mac OS Big Sur

[aminadibi]

Following #268 using Mac OS Big Sur with the m1 processor running R and gfortran under Rosetta, I get the error "*** C++11 compiler required; enable C++11 mode in your compiler, or use an earlier version of Armadillo" trying to compile the following helloworld file:

#include <RcppArmadillo.h>   

// [[Rcpp::depends(RcppArmadillo)]]

// [[Rcpp::export]]
void hello_world() {
  Rcpp::Rcout << "Hello World!" << std::endl;  
}

// After compile, this function will be immediately called using
// the below snippet and results will be sent to the R console.

/*** R
hello_world() 
*/

Been on it for hours now and can't figure out what is it that I'm missing.
Here's the error:

> Rcpp::sourceCpp('./src/helloworld.cpp')
In file included from helloworld.cpp:1:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/RcppArmadillo.h:31:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/RcppArmadilloForward.h:49:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo:21:
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/compiler_check.hpp:50:4: error: "*** C++11 compiler required; enable C++11 mode in your compiler, or use an earlier version of Armadillo"
  #error "*** C++11 compiler required; enable C++11 mode in your compiler, or use an earlier version of Armadillo"
   ^
In file included from helloworld.cpp:1:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/RcppArmadillo.h:31:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/RcppArmadilloForward.h:49:
In file included from /Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo:85:
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:149:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:150:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:151:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:161:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:162:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:163:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = true;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:173:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:174:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = true;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:175:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:185:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = true;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:186:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:187:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:197:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = T1::is_row;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:198:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = T1::is_col;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:199:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = T1::is_xvec;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:209:12: error: unknown type name 'constexpr'
    static constexpr bool is_row  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:210:12: error: unknown type name 'constexpr'
    static constexpr bool is_col  = false;
           ^
/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include/armadillo_bits/arma_forward.hpp:211:12: error: unknown type name 'constexpr'
    static constexpr bool is_xvec = false;
           ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
make: *** [helloworld.o] Error 1
clang++ -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include   -I"/Library/Frameworks/R.framework/Versions/4.0/Resources/library/Rcpp/include" -I"/Library/Frameworks/R.framework/Versions/4.0/Resources/library/RcppArmadillo/include" -I"/Users/amin/armatest/src" -I"/Users/amin/armatest/src/../inst/include" -I/usr/local/include   -fPIC  -Wall -g -O2  -c helloworld.cpp -o helloworld.o
Error in Rcpp::sourceCpp("./src/helloworld.cpp") : 
  Error 1 occurred building shared library.

I have gfortran 10.2.0 through fxcoudert and clang 12.0.0 through Xcode

% gfortran --version            
GNU Fortran (GCC) 10.2.0

% clang --version
Apple clang version 12.0.0 (clang-1200.0.32.28)
Target: arm64-apple-darwin20.2.0

Here is my environment:

> sessionInfo()
R version 4.0.3 (2020-10-10)
Platform: x86_64-apple-darwin17.0 (64-bit)
Running under: macOS Big Sur 10.16

Matrix products: default
LAPACK: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib

locale:
[1] en_CA.UTF-8/en_CA.UTF-8/en_CA.UTF-8/C/en_CA.UTF-8/en_CA.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

loaded via a namespace (and not attached):
[1] compiler_4.0.3 tools_4.0.3   

[kevinushey]

Works fine for me on Big Sur. The main thing that stands out is that your compile statement isn't requesting C++11 (or greater). E.g. when I run sourceCpp(), I see:

clang++ -mmacosx-version-min=10.13 -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG -I../inst/include -I"/Users/kevinushey/Library/R/4.0/library/Rcpp/include" -I"/Users/kevinushey/Library/R/4.0/library/RcppArmadillo/include" -I"/Users/kevinushey/scratch" -I/usr/local/include -fPIC -g -O3 -pipe -Wall -pedantic -c hello.cpp -o hello.o

Note the -std=gnu++11. That comes from R's Makevars:

CXX = clang++ -mmacosx-version-min=10.13 -std=gnu++11

which makes me suspect you may have overridden CXX in your own ~/.R/Makevars.

FWIW you can force C++11 with:

// [[Rcpp::plugins(cpp11)]]

in your script as an alternate way forward.

[aminadibi]

That worked! Thank you so much!

[eddelbuettel]

@kevinushey Isn't the plugin redundant as R now enforces C++11 as a minimum standard? Or did you suggest it as a fudge in case a local ~/.R/Makevars shadows / invalidates the global setting?

[kevinushey]

Right, it's a fudge in case the user has overridden the default compiler and removed the flags forcing C++11.

[aminadibi]

So, to be clear I had not manually overridden the default. After a fresh install of R and Xcode on a new laptop, there was a ~/.R/Makevars with:

CC=clang
CXX=clang++

[eddelbuettel]

See #324 (comment) where @kevinushey explains what gets replaced. You are loosing that selection of C++11. Which is the issue that brought you here. Makes sense? So not pointing fingers at you per se but maybe at whoever setup of the installer?

[aminadibi]

Of course @eddelbuettel. I am just curious why would R create a Makevars that overrides C++11?

[eddelbuettel]

"It doesn't." (Speaking at the Debian maintainre for the build of R.) R would never touch ~/.R/Makevars.

Maybe it's XCode, maybe it's a (ahem) feature in the macOS build. I have no idea.

[kevinushey]

That might've been done by RStudio actually (if you're using that). Will have to investigate.

(That's an old leftover from the days when Apple switched from gcc to clang)

[kevinushey]

Just to close the loop, this was quite likely generated by RStudio:

rstudio/rstudio#8800

so we'll have to fix there. Sorry for the trouble; this fix was appropriate ~5 years ago but no longer now :-/

[eddelbuettel]

Glad we found it!

[aminadibi]

Thanks for following up with this @kevinushey! Will save so many from so much trouble.

[Tomtao626]

-std=c++11

[eddelbuettel]

@Tomtao626 R does that automatically for at least two years now, in fact it by now defaults to C++14. The root cause is still the need for recent-enough compiler on the machine.