[Rcpp-devel] Resolving NativeSymbolInfos from Rcpp

[Romain Francois]

Le 09/06/10 03:04, Davor Cubranic a écrit :
>
> Hi there,
>
> I have a question about the murky world of R internals, DLLs, and their interaction with Rcpp.
>
> There are some C routines in the 'stats' package that I would like to call directly from my Rcpp-based package, e.g., loess_raw. However, 'stats' only exposes them to R callers, not C or C++. (I.e., it does not use R_RegisterCCallable, but they are among R_CMethodDef's passed in R_registerRoutines.)
>
> Reading the information on writing R extensions, it sounds like there may not be a way to get to the address of an object in another package's DLL. (In this case, in stats.so.) However, there is a NativeSymbolInfo for stats:::R_loess_raw, which includes all sorts of info about the C method. Is there a way that this can be used to get a function pointer to it from within my code? And if this is too unportable, is there a cleaner way?
>
> Thanks,
>
> Davor

Hi,

I see

 > getNativeSymbolInfo( "loess_raw" )
$name
[1] "loess_raw"

$address
<pointer: 0x103092820>
attr(,"class")
[1] "NativeSymbol"

$package
DLL name: stats
Filename:
 
/Library/Frameworks/R.framework/Resources/library/stats/libs/x86_64/stats.so
Dynamic lookup: FALSE

$numParameters
[1] 24

attr(,"class")
[1] "CRoutine"         "NativeSymbolInfo"

So I'd probably look into the implementation of getNativeSymbolInfo 
(R_getSymbol in file Rdynload.c) and figure out what sort of pointer is 
the $address here. once you know that I suppose you can use it.

There is a good chance the pointer is a DL_FUNC. You probably want to 
look at the Rdynpriv.h file too.

Maybe this question is more suited to R-devel.

Romain

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Romain Francois
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