[Rd] R_MakeExternalPtr 'tag' argument

Simon Urbanek simon.urbanek at r-project.org
Sat Nov 14 14:43:04 CET 2015

On Nov 13, 2015, at 3:58 PM, William Dunlap <wdunlap at tibco.com> wrote:

> Most packages that use the R_MakeExternalPtr function use
> Rf_install("pkgSpecificString") for its 'tag' argument (if they don't use
> R_NilValue).  A few use Rf_mkChar("pkgSpecificString").
> Is there any reason to prefer one over the other?

I think Luke is the definite authority, but IMHO using CHARSXP is illegal since you can only store CHARSXP in STRSXP. R-exts allows "ordinary R objects" so presumably mkString() would be legal.


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