[Rcpp-devel] useDynLib

Davor Cubranic cubranic at stat.ubc.ca
Fri Apr 1 20:15:16 CEST 2011

On 2011-03-31, at 8:12 PM, Sean Robert McGuffee wrote:

> Thanks for the info about modularity. I'll definitely be wikipedia'ing that.
> Also, thanks for clarifying the package author thing--I literally was
> imagining some sort of function that writes something related to packages.

You know, I can see that, esp. in the context of the rest of that section. I'll send a suggestion to the manual maintainers to consider using a clearer expression.

> In particular with useDynLib, what type of argument(s) go(es) in it?
> For example, do I literally copy a file object into it somehow?

What I have in my NAMESPACEs, and is used in the example in section 1.6.4 of the manual, is just the name of the DLL without the extension. And it's a symbol, rather than a string, so no quotes.

> For example, say I want to link against libpng14.
> On the machine I'm sitting at, it's located at:
> /usr/local/lib/libpng14.a
> How would I use useDynLib in that case?

Aha, you may not need to dive into "useDynLib"s dark corners after all. I only use "useDynLib" to link to my package's own library. For linking to a library provided by another package, such as Rcpp or a system library, I have a src/Makevars in my package that sets the right "-l" compiler switches and assigns them to PKG_LIBS variable. See section "1.2.1 Using Makevars" in R-exts. It goes into way more detail than you'll need (ignore all stuff about "configure" for now), or see how Rcpp.package.skeleton creates a Makevars file that has all the switches to link against Rcpp's DLL. (In their case it's a bit more general, and you may really need nothing more than "PKG_LIBS=-lpng14".)

I admit I approach this on a need-to-know basis myself, IOW only about as far as I need to make my code work. But it does work, and I have also seen it used in a number of packages I've looked at, so I don't think it's too far off the mark. Others on the list can chime in if I'm grossly misrepresenting the linking mechanism or what you should do in your case.


More information about the Rcpp-devel mailing list