problems with creating a package when putting C++ functions in `utils.h`

[paciorek]

I am hoping this just relates to some aspect of organizing files that @perrydv can help me with at some point (this is not urgent).

Two problem cases:

1. In the TBB work I created a C++ function getNumThreads in utils.h. This works fine when compiling on the fly, but when I try to create a package (with nCompile(...,package = TRUE) or writePackage, I get this:

g++ -std=gnu++17 -shared -L/usr/lib/R/lib -Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro -o foo1.so R_interfaces_c_.o RcppExports.o nClass_1_c_.o rcpp_hello_world.o -L/usr/lib/R/lib -lR
/usr/bin/ld: RcppExports.o: in function `getNumThreads(double)':
/accounts/vis/paciorek/R/x86_64-pc-linux-gnu-library-ubuntu-24.04/4.5/nCompiler/include/nCompiler/utils.h:1: multiple definition of `getNumThreads(double)'; R_interfaces_c_.o:/accounts/vis/paciorek/R/x86_64-pc-linux-gnu-library-ubuntu-24.04/4.5/nCompiler/include/nCompiler/utils.h:1: first defined here
/usr/bin/ld: nClass_1_c_.o: in function `getNumThreads(double)':
/accounts/vis/paciorek/R/x86_64-pc-linux-gnu-library-ubuntu-24.04/4.5/nCompiler/include/nCompiler/utils.h:1: multiple definition of `getNumThreads(double)'; R_interfaces_c_.o:/accounts/vis/paciorek/R/x86_64-pc-linux-gnu-library-ubuntu-24.04/4.5/nCompiler/include/nCompiler/utils.h:1: first defined here
collect2: error: ld returned 1 exit status

2. In the messaging work I created functions like nStop in utils.h. Again it's fine when compiling on the fly, but when creating a package:

nFun_2_c_.cpp: In function ‘void nFun_2(Eigen::Tensor<double, 1>)’:
nFun_2_c_.cpp:27:1: error: ‘_nCompiler_global_output’ was not declared in this scope
   27 | _nCompiler_global_output << "problem: "<<y<<" "<<x+y; nStop(_nCompiler_global_output);
      | ^~~~~~~~~~~~~~~~~~~~~~~~
nFun_2_c_.cpp:27:55: error: ‘nStop’ was not declared in this scope; did you mean ‘nStep’?
   27 | _nCompiler_global_output << "problem: "<<y<<" "<<x+y; nStop(_nCompiler_global_output);
      |                                                       ^~~~~
      |                                                       nStep

[perrydv]

@paciorek for the first issue can you try declaring getNumThreads as inline (Add inline at the start of its declaration like inline int getNumThreads() ...

For the second issue sorry I haven't look at this before. We have been using Rcpp::stop in the static C++ code so that would probably work for code-generation from nStop and be simpler than the nimble approach of making our own output stream.

[paciorek]

Thanks, the inline for getNumThreads works.

The second issue was a silly error on my part and is actually fine.

More general note, in the messaging branch I have a bunch of work involving stop, warn, and a messaging system that use our own output stream. So we'll want to discuss this further.