[R-pkg-devel] "Writing R Extensions" manual needs update [was: Error handling in C code]

[Tomas Kalibera]

On 6/24/24 08:25, Agner Fog wrote:
> Jarrod Hadfield wrote:
>
>> Using Rf_error() rather than error() fixed the problem. Not sure why the problem was only flagged on Debian, but it
>> seems to have been triggered by R_NO_REMAP being defined (which will be default in R 4.5.0).
> I had the same problem. A lot of functions in my package 'BiasedUrn' had
> to be changed to the Rf_ prefix names. It took me a long time to figure
> out because I couldn't find proper documentation anywhere.
>
> Apparently, the remapped function names can no longer be used. The
> consequences of this change are far-reaching: /all /existing packages
> containing C++ code must be modified to use the Rf_ function names for
> /all /R API function calls.
>
> This change is not properly documented. The "Writing R Extensions"
> manual still lists the remapped function names without Rf_ prefix. This
> manual needs to be updated to replace all remapped function names with
> the Rf_ prefix names. I also think that it needs to add instructions on
> how to fix legacy C++ code, including a list of the function names that
> need to be changed. I cannot see where the change in R_NO_REMAP  is
> documented.
>
> I don't know why R_NO_REMAP is currently defined in Debian but not in
> Windows, but the consequence is that the "Writing R Extensions" manual
> must be updated now, and not wait for R version 4.5.0.
>
> I think there should be a way to enable the remapped function names for
> the sake of compatibility with legacy code. What should we do with old
> packages where the maintainer is no longer contactable or is somebody
> less competent than the original programmer?
>
> Does it work to  #undef R_NO_REMAP  before  #include <R.h> ?
>
> Let me suggest a simple solution: Define a preprocessing macro
> R_FORCE_REMAP which can override R_NO_REMAP. Legacy C++ code can then be
> fixed by adding a Makevars file with -DR_FORCE_REMAP
>
> You may also reconsider the decision to add R_NO_REMAP as standard.
>
> I have written to the maintainers and asked them to change the "Writing
> R Extensions" manual, but got no reponse.

In principle it is the NEWS file that gives hints about important 
changes and then one can find the details in Writing R Extensions.  The 
NEWS file as of mid-April says that "R CMD check --as-cran" will compile 
C++ code with -DR_NO_REMAP. And then in Writing R Extensions, one can 
read about what is R_NO_REMAP and that this has been planned to become 
the default in the future. It is an important thing to do for the 
maintainability of the package space: the situation with name clashes 
with system headers (typically appearing just on some platforms) has 
only been getting worse.

Best
Tomas

>
> - Agner
> 	[[alternative HTML version deleted]]
>
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