[Rd] documentation of .C (PR#9948)

Thomas Lumley tlumley at u.washington.edu
Wed Oct 10 20:10:50 CEST 2007

On Wed, 10 Oct 2007, schlather at math.uni-goettingen.de wrote:

> Full_Name: Martin Schlather
> Version: R version 2.7.0 Under development (unstable) (2007-10-01 r43043)
> OS: Linux
> Submission from: (NULL) (
> Hi,
> There are 2 dangers with using 'DUP=FALSE' mentioned:
>  * formal arguments
>  * lists
> Would you also mention a third one, namely
> that values in R are now only referenced  whenever
> possible and not always copied; hence .C(..., DUP=FALSE)
> may change the values of other local variables.

How about a warning like

"if you pass a local variable to .C/.Fortran with 
DUP=FALSE, your compiled code can alter the local variable and not just 
the copy in the return list. "


(copied from ?.C, of course)

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