[R-pkg-devel] How to use O4 flag in an RCpp project?

[Dirk Eddelbuettel]

On 20 May 2025 at 19:39, Peiyuan Zhu wrote:
| How to use the O4 flag in an RCpp project? Every time when I load_all it
| starts using the O2 flag or the debug flag. What should I put into Makevar?
| Can I still do remote::install.github(...)?

Given that this mailing list can need explicit approval on eg initial posts,
your post here precedes these two follow-ups you posted since. So by now this
same question by you has also been asked

 - on Stackoverflow about twelve hours ago; you were told that it is not a
   genuinely well-formed question (and StackOverflow can be funny that way, I
   stop interacting there for that reason). The URL is at
   https://stackoverflow.com/questions/79631329/how-to-use-o4-flag-in-rcpp-project

 - on GitHub at the Rcpp repo also about twelve hours ago, and Kevin gave
   you fairly extensive feedback saying that it isn't really a Rcpp question,
   and also closed it,  see https://github.com/RcppCore/Rcpp/issues/1383
   I also gave you some feedback there six hours ago, in essence the issue is
   one that has nothing to do with Rcpp and is about how R calls make to
   generate the compilation, see
   https://github.com/RcppCore/Rcpp/issues/1383#issuecomment-2896674848 

The underlying issue ("how do I override compiler switches") has been
discussed elsewhere too, likely here and earlier on the (older) list r-devel.
In short, "no we cannot remove -O2" and "no it does not matter" because (if I
recall correctly) the right-most value wins. The documentation of `make`
probably has more. Otherwise you probably want to consult the "Writing R
Extensions" manual. 

Hope this helps.

Dirk

-- 
dirk.eddelbuettel.com | @eddelbuettel | edd using debian.org