An installation error: 'Expected in: flat namespace'

[sentian]

I got a bunch of warnings and an error when installing the package from source (details below). I'm on Mac OS 10.13.4 and R 3.5.0.

* installing *source* package ‘RcppArmadillo’ ...
** package ‘RcppArmadillo’ successfully unpacked and MD5 sums checked
checking whether the C++ compiler works... yes
checking for C++ compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C++ compiler... yes
checking whether /usr/local/bin/g++-8 accepts -g... yes
checking how to run the C++ preprocessor... /usr/local/bin/g++-8 -E
checking whether we are using the GNU C++ compiler... (cached) yes
checking whether /usr/local/bin/g++-8 accepts -g... (cached) yes
checking whether g++ version is sufficient... yes, with OpenMP as version 8.1.0
checking for macOS... found
checking for macOS Apple compiler... not found
checking LAPACK_LIBS... R-supplied partial LAPACK found
configure: WARNING: Some complex-valued LAPACK functions may not be available
checking for OpenMP... found and suitable
configure: creating ./config.status
config.status: creating inst/include/RcppArmadilloConfigGenerated.h
config.status: creating src/Makevars
** libs
/usr/local/bin/g++-8 -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG  -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include  -I../inst/include -fopenmp -fPIC  -Wall -g -O2 -c RcppArmadillo.cpp -o RcppArmadillo.o
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/RcppCommon.h:76,
                 from ../inst/include/RcppArmadilloForward.h:26,
                 from ../inst/include/RcppArmadillo.h:31,
                 from RcppArmadillo.cpp:22:
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h: In function 'std::__cxx11::string Rcpp::sprintf(const char*, ...)':
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h:30:12: warning: unnecessary parentheses in declaration of 'ap' [-Wparentheses]
     va_list(ap);
            ^
/usr/local/bin/g++-8 -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG  -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include  -I../inst/include -fopenmp -fPIC  -Wall -g -O2 -c RcppExports.cpp -o RcppExports.o
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/RcppCommon.h:76,
                 from ../inst/include/RcppArmadilloForward.h:26,
                 from ../inst/include/RcppArmadillo.h:31,
                 from RcppExports.cpp:4:
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h: In function 'std::__cxx11::string Rcpp::sprintf(const char*, ...)':
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h:30:12: warning: unnecessary parentheses in declaration of 'ap' [-Wparentheses]
     va_list(ap);
            ^
/usr/local/bin/g++-8 -std=gnu++11 -I"/Library/Frameworks/R.framework/Resources/include" -DNDEBUG  -I"/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include" -I/usr/local/include  -I../inst/include -fopenmp -fPIC  -Wall -g -O2 -c fastLm.cpp -o fastLm.o
In file included from /Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/RcppCommon.h:76,
                 from ../inst/include/RcppArmadilloForward.h:26,
                 from ../inst/include/RcppArmadillo.h:31,
                 from fastLm.cpp:22:
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h: In function 'std::__cxx11::string Rcpp::sprintf(const char*, ...)':
/Library/Frameworks/R.framework/Versions/3.5/Resources/library/Rcpp/include/Rcpp/sprintf.h:30:12: warning: unnecessary parentheses in declaration of 'ap' [-Wparentheses]
     va_list(ap);
            ^
In file included from ../inst/include/armadillo:683,
                 from ../inst/include/RcppArmadilloForward.h:46,
                 from ../inst/include/RcppArmadillo.h:31,
                 from fastLm.cpp:22:
../inst/include/armadillo_bits/glue_times_meat.hpp: In instantiation of 'static void arma::glue_times_redirect2_helper<do_inv_detect>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; bool do_inv_detect = false; typename T1::elem_type = double]':
../inst/include/armadillo_bits/glue_times_meat.hpp:112:44:   required from 'static void arma::glue_times_redirect2_helper<true>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:347:74:   required from 'static void arma::glue_times_redirect<2>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:441:36:   required from 'static void arma::glue_times::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/Mat_meat.hpp:4972:19:   required from 'arma::Mat<eT>::Mat(const arma::Glue<T1, T2, glue_type>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; glue_type = arma::glue_times; eT = double]'
../inst/include/armadillo_bits/Proxy.hpp:607:10:   required from 'arma::Proxy<arma::Glue<T1, T2, glue_type> >::Proxy(const arma::Glue<T1, T2, glue_type>&) [with T1 = arma::Mat<double>; T2 = arma::Col<double>; glue_type = arma::glue_times]'
../inst/include/armadillo_bits/eGlue_meat.hpp:35:12:   required from 'arma::eGlue<T1, T2, eglue_type>::eGlue(const T1&, const T2&) [with T1 = arma::Col<double>; T2 = arma::Glue<arma::Mat<double>, arma::Col<double>, arma::glue_times>; eglue_type = arma::eglue_minus]'
../inst/include/armadillo_bits/operator_minus.hpp:134:10:   required from 'typename arma::enable_if2<((arma::is_arma_type<T1>::value && arma::is_arma_type<T2>::value) && arma::is_same_type<typename T1::elem_type, typename T2::elem_type>::value), const arma::eGlue<T1, T2, arma::eglue_minus> >::result arma::operator-(const T1&, const T2&) [with T1 = arma::Col<double>; T2 = arma::Glue<arma::Mat<double>, arma::Col<double>, arma::glue_times>; typename arma::enable_if2<((arma::is_arma_type<T1>::value && arma::is_arma_type<T2>::value) && arma::is_same_type<typename T1::elem_type, typename T2::elem_type>::value), const arma::eGlue<T1, T2, arma::eglue_minus> >::result = const arma::eGlue<arma::Col<double>, arma::Glue<arma::Mat<double>, arma::Col<double>, arma::glue_times>, arma::eglue_minus>]'
fastLm.cpp:30:31:   required from here
../inst/include/armadillo_bits/glue_times_meat.hpp:39:14: warning: variable 'use_alpha' set but not used [-Wunused-but-set-variable]
   const bool use_alpha = partial_unwrap<T1>::do_times || partial_unwrap<T2>::do_times;
              ^~~~~~~~~
../inst/include/armadillo_bits/glue_times_meat.hpp: In instantiation of 'static void arma::glue_times_redirect2_helper<do_inv_detect>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Glue<arma::Mat<double>, arma::Op<arma::Col<double>, arma::op_diagmat>, arma::glue_times_diag>; T2 = arma::Op<arma::Mat<double>, arma::op_htrans>; bool do_inv_detect = false; typename T1::elem_type = double]':
../inst/include/armadillo_bits/glue_times_meat.hpp:112:44:   required from 'static void arma::glue_times_redirect2_helper<true>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Glue<arma::Mat<double>, arma::Op<arma::Col<double>, arma::op_diagmat>, arma::glue_times_diag>; T2 = arma::Op<arma::Mat<double>, arma::op_htrans>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:347:74:   required from 'static void arma::glue_times_redirect<2>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Glue<arma::Mat<double>, arma::Op<arma::Col<double>, arma::op_diagmat>, arma::glue_times_diag>; T2 = arma::Op<arma::Mat<double>, arma::op_htrans>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:441:36:   required from 'static void arma::glue_times::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Glue<arma::Mat<double>, arma::Op<arma::Col<double>, arma::op_diagmat>, arma::glue_times_diag>; T2 = arma::Op<arma::Mat<double>, arma::op_htrans>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/Mat_meat.hpp:4989:19:   required from 'arma::Mat<eT>& arma::Mat<eT>::operator=(const arma::Glue<T1, T2, glue_type>&) [with T1 = arma::Glue<arma::Mat<double>, arma::Op<arma::Col<double>, arma::op_diagmat>, arma::glue_times_diag>; T2 = arma::Op<arma::Mat<double>, arma::op_htrans>; glue_type = arma::glue_times; eT = double]'
../inst/include/armadillo_bits/op_pinv_meat.hpp:128:11:   required from 'static bool arma::op_pinv::apply_direct(arma::Mat<typename T1::elem_type>&, const arma::Base<typename T1::elem_type, T1>&, typename T1::pod_type, bool) [with T1 = arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>; typename T1::elem_type = double; typename T1::pod_type = double]'
../inst/include/armadillo_bits/op_pinv_meat.hpp:36:44:   [ skipping 4 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
../inst/include/armadillo_bits/Mat_meat.hpp:4593:17:   required from 'arma::Mat<eT>::Mat(const arma::Op<T1, op_type>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>; op_type = arma::op_diagvec; eT = double]'
../inst/include/armadillo_bits/Proxy.hpp:1121:10:   required from 'arma::Proxy_diagvec_expr<arma::Op<T1, arma::op_diagvec> >::Proxy_diagvec_expr(const arma::Op<T1, arma::op_diagvec>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>]'
../inst/include/armadillo_bits/Proxy.hpp:1168:22:   required from 'arma::Proxy<arma::Op<T1, arma::op_diagvec> >::Proxy(const arma::Op<T1, arma::op_diagvec>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>]'
../inst/include/armadillo_bits/eOp_meat.hpp:36:15:   required from 'arma::eOp<T1, eop_type>::eOp(const T1&, typename T1::elem_type) [with T1 = arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>; eop_type = arma::eop_scalar_times; typename T1::elem_type = double]'
../inst/include/armadillo_bits/operator_times.hpp:45:10:   required from 'typename arma::enable_if2<arma::is_arma_type<T1>::value, const arma::eOp<T1, arma::eop_scalar_times> >::result arma::operator*(typename T1::elem_type, const T1&) [with T1 = arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>; typename arma::enable_if2<arma::is_arma_type<T1>::value, const arma::eOp<T1, arma::eop_scalar_times> >::result = const arma::eOp<arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>, arma::eop_scalar_times>; typename T1::elem_type = double]'
fastLm.cpp:35:86:   required from here
../inst/include/armadillo_bits/glue_times_meat.hpp:39:14: warning: variable 'use_alpha' set but not used [-Wunused-but-set-variable]
../inst/include/armadillo_bits/glue_times_meat.hpp: In instantiation of 'static void arma::glue_times_redirect2_helper<do_inv_detect>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; bool do_inv_detect = false; typename T1::elem_type = double]':
../inst/include/armadillo_bits/glue_times_meat.hpp:112:44:   required from 'static void arma::glue_times_redirect2_helper<true>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:347:74:   required from 'static void arma::glue_times_redirect<2>::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/glue_times_meat.hpp:441:36:   required from 'static void arma::glue_times::apply(arma::Mat<typename T1::elem_type>&, const arma::Glue<T1, T2, arma::glue_times>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; typename T1::elem_type = double]'
../inst/include/armadillo_bits/Mat_meat.hpp:4972:19:   required from 'arma::Mat<eT>::Mat(const arma::Glue<T1, T2, glue_type>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; glue_type = arma::glue_times; eT = double]'
../inst/include/armadillo_bits/Proxy.hpp:607:10:   required from 'arma::Proxy<arma::Glue<T1, T2, glue_type> >::Proxy(const arma::Glue<T1, T2, glue_type>&) [with T1 = arma::Op<arma::Mat<double>, arma::op_htrans>; T2 = arma::Mat<double>; glue_type = arma::glue_times]'
../inst/include/armadillo_bits/op_pinv_meat.hpp:58:19:   [ skipping 5 instantiation contexts, use -ftemplate-backtrace-limit=0 to disable ]
../inst/include/armadillo_bits/Mat_meat.hpp:4593:17:   required from 'arma::Mat<eT>::Mat(const arma::Op<T1, op_type>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>; op_type = arma::op_diagvec; eT = double]'
../inst/include/armadillo_bits/Proxy.hpp:1121:10:   required from 'arma::Proxy_diagvec_expr<arma::Op<T1, arma::op_diagvec> >::Proxy_diagvec_expr(const arma::Op<T1, arma::op_diagvec>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>]'
../inst/include/armadillo_bits/Proxy.hpp:1168:22:   required from 'arma::Proxy<arma::Op<T1, arma::op_diagvec> >::Proxy(const arma::Op<T1, arma::op_diagvec>&) [with T1 = arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>]'
../inst/include/armadillo_bits/eOp_meat.hpp:36:15:   required from 'arma::eOp<T1, eop_type>::eOp(const T1&, typename T1::elem_type) [with T1 = arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>; eop_type = arma::eop_scalar_times; typename T1::elem_type = double]'
../inst/include/armadillo_bits/operator_times.hpp:45:10:   required from 'typename arma::enable_if2<arma::is_arma_type<T1>::value, const arma::eOp<T1, arma::eop_scalar_times> >::result arma::operator*(typename T1::elem_type, const T1&) [with T1 = arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>; typename arma::enable_if2<arma::is_arma_type<T1>::value, const arma::eOp<T1, arma::eop_scalar_times> >::result = const arma::eOp<arma::Op<arma::Op<arma::Glue<arma::Op<arma::Mat<double>, arma::op_htrans>, arma::Mat<double>, arma::glue_times>, arma::op_pinv>, arma::op_diagvec>, arma::eop_scalar_times>; typename T1::elem_type = double]'
fastLm.cpp:35:86:   required from here
../inst/include/armadillo_bits/glue_times_meat.hpp:39:14: warning: variable 'use_alpha' set but not used [-Wunused-but-set-variable]
/usr/local/bin/g++-8 -std=gnu++11 -dynamiclib -Wl,-headerpad_max_install_names -undefined dynamic_lookup -single_module -multiply_defined suppress -L/Library/Frameworks/R.framework/Resources/lib -L/usr/local/lib -o RcppArmadillo.so RcppArmadillo.o RcppExports.o fastLm.o -fopenmp -L/Library/Frameworks/R.framework/Resources/lib -lRlapack -L/Library/Frameworks/R.framework/Resources/lib -lRblas -L/usr/local/gfortran/lib/gcc/x86_64-apple-darwin15/6.1.0 -L/usr/local/gfortran/lib -lgfortran -lquadmath -lm -F/Library/Frameworks/R.framework/.. -framework R -Wl,-framework -Wl,CoreFoundation
installing to /Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo/libs
** R
** inst
** byte-compile and prepare package for lazy loading
** help
*** installing help indices
** building package indices
** installing vignettes
** testing if installed package can be loaded
Error: package or namespace load failed for ‘RcppArmadillo’ in dyn.load(file, DLLpath = DLLpath, ...):
 unable to load shared object '/Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo/libs/RcppArmadillo.so':
  dlopen(/Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo/libs/RcppArmadillo.so, 6): Symbol not found: __ZNKSt13random_device13_M_getentropyEv
  Referenced from: /Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo/libs/RcppArmadillo.so
  Expected in: flat namespace
 in /Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo/libs/RcppArmadillo.so
Error: loading failed
Execution halted
ERROR: loading failed
* removing ‘/Library/Frameworks/R.framework/Versions/3.5/Resources/library/RcppArmadillo’```

[eddelbuettel]

You use a compiler nobody else uses on that platform, so if things break -- you get to keep the pieces.

We work hard to support what CRAN provides as a setup. We don't have the resources for the cross products of all hardware times all OSs times all compilers.

[eddelbuettel]

True but not that it matters -- the object code was still built. And then failed to load:

Symbol not found: __ZNKSt13random_device13_M_getentropyEv

As it is a wee bit tricky to randomly mix and match. Which is why the documentation never says "pick a random compiler version from brew". Actually, AFAIK, it never suggests brew in the first place but then I am a little fuzzy as I have no systems made in Cupertino...

I think I should just close this.

[kthohr]

The linking error looks weird, perhaps due to a conflict between libc++ and libstdc++.

Can you try the following from terminal?

cd ~/Desktop
curl -O https://cran.r-project.org/src/contrib/RcppArmadillo_0.8.500.0.tar.gz
tar -zxvf RcppArmadillo_0.8.500.0.tar.gz
R CMD INSTALL RcppArmadillo
# The above will fail, which is expected
nm -g -m ./RcppArmadillo/src/RcppArmadillo.so > ./rcpp_arma_symbols.txt
otool -L ./RcppArmadillo/src/RcppArmadillo.so

Then paste the output of the final command---it will look something like this:

RcppArmadillo.so:
	RcppArmadillo.so (compatibility version 0.0.0, current version 0.0.0)
	...
	/opt/local/lib/libgcc/libgfortran.4.dylib (compatibility version 5.0.0, current version 5.0.0)
	/opt/local/lib/libgcc/libquadmath.0.dylib (compatibility version 1.0.0, current version 1.0.0)
	/usr/lib/libSystem.B.dylib (...)
	libR.dylib (compatibility version 3.6.0, current version 3.6.0)
	/System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (...)
	/opt/local/lib/libomp/libomp.dylib (compatibility version 5.0.0, current version 5.0.0)
	/usr/lib/libc++.1.dylib (...)

And attach rcpp_arma_symbols.txt if you can.

[kevinushey]

Yes indeed. If you try to build R packages with gcc on macOS, you usually have to explicitly request libstdc++ rather than libc++.

Note that mixing R packages built with libc++ versus libstdc++ can cause lots of subtle issues (e.g. exception ABI differences when exceptions get thrown across module boundaries) so I / we generally don't recommend using gcc on macOS unless you have a very good reason.

[eddelbuettel]

So let's call this user error, and close it. This can happen -- picking a common compiler may seem like a good idea -- but it really is a wee bit more complicated behind the scenes. So please see the R documentation on what toolchains to use where.

[sentian]

Thank you for the help, guys. I probably shouldn't use gcc, especially gcc 8.1 on MAC OS. I thought it's pretty much the same as clang.

As per @kevinushey 's recommendation and also related to @kthohr 's thread in the my previous post, I switched from gcc to clang6. Now it has no problem at all during the installation.

[eddelbuettel]

We should probably make it clearer somewhere that clang* really is the expected compiler.

@kthor / @coatless / @kevinushey How about it we bail / error if we see 'not clang' under macOS ?

[kthohr]

I think an big warning alongs the lines of, 'Undocumented compiler setup on macOS detected; if things break, you get to keep all the pieces.' :-)

Power users might complain about a hard error?

[eddelbuettel]

Agreed. A message may be useful, enforced stop may be too harsh.