[R-pkg-devel] Compiling error with the new R.h header (R-devel 3.3.0 for Windows) when using the C++ function isnan() of <math.h>

[Dirk Eddelbuettel]

On 20 April 2016 at 14:28, Antonio Canale wrote:
| Dear all,
| 
| my problem is related to the new version of my msBP package but it
| actually applies also to the current version uploaded on CRAN
| (https://cran.r-project.org/web/checks/check_results_msBP.html).
| 
| It turns out that the package cannot be compiled under the new R-devel
| for windows.
| 
| The problem is related to the isnan() function of <math.h> library of
| C++ which I call twice in one of my C++ scripts.
| 
| Consider the function below as MWE
| 
| #include<stdio.h>
| #include<stdlib.h>
| #include<math.h>
| #include<R.h>
| #include<Rmath.h>
| extern "C"{
| void gibbs(double *A)
| {
| if(isnan(A[i]) || (A[i]<=0))
| { do stuff }
| }
| }
| 
| Precisely, the error that I get is reported at
| https://www.r-project.org/nosvn/R.check/r-devel-windows-ix86+x86_64/msBP-00install.html

Newer compilers get you more stringent enforcement of standards, so it is now
std::isnan.  That would be the same with g++-4.9 on other OSs.

You could avoid the whole issue and just use the macros included via the R
headers.  Or you could use a certain package ending in 'pp' which helps with
C++ and R integration as it too gives you a few helpers ...
 
| I've have found in the R-devel blog and check myself that from R
| version 3.3.0 the header  file R.h is changed. In particular it is now
| going to include the C++ versions of system header ‘<cmath>’ rather
| than the legacy header ‘<math.h> which seems to be the source of my
| problem.

That is good C++ practice.
 
| However I cannot understand why it causes the error and in particular
| why it is happening *only under windows* and not under other OS. I've
| check my new package both in OS X and Ubuntu (with R-devel) and
| everything is OK. It also compiles fine in Windows under R.3.2.5.

Not an R version issue but a compiler issue.

Dirk

-- 
http://dirk.eddelbuettel.com | @eddelbuettel | edd at debian.org