Dynamically load user32.dll from R & call external function

Question

I try to access user32.dll functions in R Session. I used the code:

dyn.load("c://windows//system32//user32.dll")
.External("MessageBeep", 0L)

But R session crashes. According to documentation .External is intended to use during R package creation. However there was no prohibition to use it as shown above.

I am using Windows 8 and RStudio (1.1.453) / R (3.5.0). Could you advise a proper way to call external Windows functions from R session?

Where do you specify the calling convention as stdcall? My guess is you can't and would need to create a wrapper dll. — David Heffernan, Aug 26 '18 at 12:07
As I understand calling conventions should be specified during compilation. And I should look either 1) to compile some package or 2) to use some external process to access to desired dll (somethin like VBA)? — Artem, Aug 26 '18 at 14:10
The calling convention of that function is stdcall. I'm not sure if R can call stdcall functions. I think it always uses cdecl. VBA isn't what you need. Which functions are you actually trying to call? — David Heffernan, Aug 26 '18 at 15:24
Thanks for the hint, I found SO post on [cdecl & stdcall](https://stackoverflow.com/questions/3404372/stdcall-and-cdecl) as well as more thoroughly try to read the R package creation documentation. I am trying to call any function from any dll function. For academic purposes. — Artem, Aug 26 '18 at 18:44

score 3 · Accepted Answer · edited Jul 31 '23 at 21:27

You are accessing the Win32 C API, thus you can load the user32.dll, and then use the Foreign {base} .C() call too access the Window32 MessageBeep function.

##Example Code

dyn.load("c://windows//system32//user32.dll")
.C("MessageBeep")

##Runtime Output

> dyn.load("c://windows//system32//user32.dll")
> .C("MessageBeep")
list()
>

You should hear the Windows Message "Beep" - Alas, I have yet to figure out how to include sounds in solutions (chuckle).

Note: I'd also recommend you take a look at the Rcpp package, I am a big fan.

Dynamically load user32.dll from R & call external function

1 Answers1