[R-package] Convert LGBM_GetLastError_R to use R built-in types

[jameslamb]

This is a small step towards #3016. This PR proposes converting LGBM_GetLastError_R (and the R function that calls it, lgb.last_error()) to use R's built-in types instead of the custom type defined in https://github.com/microsoft/LightGBM/blob/91f72e2a8c8b1e5433d30d3891923b3a067402a6/R-package/src/R_object_helper.h.

Notes for Reviewers

This PR is not dependent on #4155. #4155 has been merged to master and this PR has been updated with it.

You can see the following to learn about the SEXPtype.

• usage:
  • https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Handling-R-objects-in-C
  • https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Garbage-Collection
  • https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Allocating-storage
  • https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Handling-character-data
• low-level details:
  • https://cran.r-project.org/doc/manuals/r-release/R-ints.html#SEXPs

[jameslamb]

Ok CI seems to be happy, so I've converted this to "ready for review".

[jameslamb]

/gha run r-valgrind

Workflow R valgrind tests has been triggered! 🚀
https://github.com/microsoft/LightGBM/actions/runs/801279370

Status: failure ❌.

[jameslamb]

/gha run r-valgrind

Workflow R valgrind tests has been triggered! 🚀
https://github.com/microsoft/LightGBM/actions/runs/801327895

Status: success ✔️.

[jameslamb]

/gha run r-solaris

Workflow Solaris CRAN check has been triggered! 🚀
https://github.com/microsoft/LightGBM/actions/runs/801445720

solaris-x86-patched: https://builder.r-hub.io/status/lightgbm_3.2.1.99.tar.gz-c0715a2abb824fce9279615c6eee11be
solaris-x86-patched-ods: https://builder.r-hub.io/status/lightgbm_3.2.1.99.tar.gz-87ffc88840e34e00bda55318b68ce94b
Reports also have been sent to LightGBM public e-mail: http://www.yopmail.com/lightgbm_rhub_checks
Status: success ✔️.

[StrikerRUS]

Very nice simplification!

[StrikerRUS]

Just a question: what is the difference between Rf_allocVector/allocVector and Rf_mkChar/mkChar?
I could find only the following link: https://www.cs.kent.ac.uk/projects/cxxr/doc/html/Rinternals_8h.html. And it looks like they are just aliases...

[jameslamb]

yep, just aliases! This #define says "use the symbols with the Rf_ prefix"

LightGBM/R-package/src/lightgbm_R.cpp

Line 15 in 1a367c6

#define R_NO_REMAP

I like that because it makes it a little more obvious which symbols are coming from R's headers.

[github-actions]

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