Message-ID: <24455.43165.512772.804445@rob.eddelbuettel.com>
Date: 2020-10-15T01:40:45Z
From: Dirk Eddelbuettel
Subject: [R-pkg-devel] C++ library USING_R
In-Reply-To: <16c3b09f-031b-5dce-643d-d292894481b5@IEEE.org>
On 14 October 2020 at 15:56, Joseph Park wrote:
| Dear R-devel,
|
| The Writing R Extensions manual states:
|
| 6.14 Platform and version information
| The header files define USING_R, which can be used to test if the code
| is indeed being used with R.
|
| I suppose this only applies to building R itself?? Or, perhaps when Rcpp
| is used for the interface, or if one includes R headers explicitly.
|
| I have a C++ library that is built with no R-dependencies, then wrapped
| with an Rcpp interface. This same library is wrapped with pybind11 in
| the Python world, and directly used in C++ applications.
|
| How can the C++ library code "know" that it's R building the library? Is
| there a platform-independent environment variable or macro?
So if I have this right you have
- a library LIB using only standard C++ components
- that you wrapped into a Python package via pybind11, and
- that you want to build for R and 'let it know it used for R'
Well I think you would then use a (wrapper) R package R_LIB and could set up
a -DR_BUILD in the src/Makevars for R_LIB. This presume that you actually
recompile LIB as part of the build; if you were to link with a static or
shared build then you could not do this _for lack of a subsequent
compilation_ and can only rely on run-time information.
Hope this helps, and that I didn't misunderstand the question.
Dirk
--
https://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org