[Rd] [External] REprintf could be caught by tryCatch(message)

[Tierney, Luke]

On Sun, 15 Sep 2019, Jan Gorecki wrote:

> Dear R-devel community,
>
> There appears to be an inconsistency in R C API about the exceptions
> that can be raised from C code.
> Mapping of R C funs to corresponding R functions is as follows.
>
> error    -> stop
> warning  -> warning
> REprintf -> message

This is wrong: REpintf is like cat with file = stderr(). If this claim
is made somewhere in R documentation please report it a a bug.

> Rprintf  -> cat
>
> Rprint/cat is of course not an exception, I listed it just for completeness.
> The inconsistency I would like to report is about REprintf. It cannot
> be caught by tryCatch(message). Warnings are errors are being caught
> as expected.
>
> Is there any chance to "fix"/"improve" REprintf so tryCatch(message)
> can catch it?

No: this is behaving as intended.

Best,

luke

> So in the example below catch(Cmessage()) would behave consistently to
> R's catch(message("a"))?
>
> Regards,
> Jan Gorecki
>
> catch = function(expr) {
>  tryCatch(expr,
>    message=function(m) cat("caught message\n"),
>    warning=function(w) cat("caught warning\n"),
>    error=function(e) cat("caught error\n")
>  )
> }
> library(inline)
> Cstop = cfunction(c(), 'error("%s\\n","a"); return R_NilValue;')
> Cwarning = cfunction(c(), 'warning("%s\\n","a"); return R_NilValue;')
> Cmessage = cfunction(c(), 'REprintf("%s\\n","a"); return R_NilValue;')
>
> catch(stop("a"))
> #caught error
> catch(warning("a"))
> #caught warning
> catch(message("a"))
> #caught message
>
> catch(Cstop())
> #caught error
> catch(Cwarning())
> #caught warning
> catch(Cmessage())
> #a
> #NULL
>
> ______________________________________________
> R-devel using r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

-- 
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:   luke-tierney using uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu