title: How to remove the warning: Rcpp/DataFrame.h:136:18: warning unused variable 'data'?
body: <p>I created an R package using RcppArmadillo from my Mac, and then built and installed it by doing the following:</p>
  <pre><code>Rcpp::compileAttributes()
  devtools::build()
  devtools::install()
  </code></pre>
  <p>However, I received several same warnings as below:</p>
  <pre><code>clang++ -std=gnu++11 -I&quot;/Library/Frameworks/R.framework/Resources/include&quot; -DNDEBUG  -I&quot;/Library/Frameworks/R.framework/Versions/3.6/Resources/library/Rcpp/include&quot; -I&quot;/Library/Frameworks/R.framework/Versions/3.6/Resources/library/RcppArmadillo/include&quot; -isysroot /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk -I/usr/local/include  -fopenmp  -fPIC  -Wall -g -O2  -c RcppExports.cpp -o RcppExports.o
  In file included from RcppExports.cpp:4:
  In file included from /Library/Frameworks/R.framework/Versions/3.6/Resources/library/RcppArmadillo/include/RcppArmadillo.h:34:
  In file included from /Library/Frameworks/R.framework/Versions/3.6/Resources/library/Rcpp/include/Rcpp.h:57:
  /Library/Frameworks/R.framework/Versions/3.6/Resources/library/Rcpp/include/Rcpp/DataFrame.h:136:18: warning: unused variable 'data' [-Wunused-variable]
              SEXP data = Parent::get__();
                   ^
  1 warning generated.
  </code></pre>
  <p>The package works fine although there are warnings during installation. Does anyone know how I can get rid of these warnings?</p>
  <p>(I tried the answer here: <a href="https://stackoverflow.com/questions/37234164/wunused-variable-errors-in-rcpp">Wunused-variable errors in Rcpp</a>, but I still got the warnings.)</p>