On 5/13/2008 7:51 AM, Nathan Harmston wrote:
Hi everyone,
I am currently trying to call some C code from R, specifically calling a
function which populates a C struct.
typedef struct{
// contents
} Model;
void test(Model *m){
// fill the struct with crap
}
I compile the C code into a shared library, which loads into R properly. My
simple test functions work (i.e adding numbers etc)
setModel <- function(){
model<-vector("list", 6)
name(model) <- c( SET THE NAMES OF THE MODEL HERE )
model
}
t <- setModel()
testcode <- function(setModel){
dyn.load("Simulation.so")
foo <- .C("test", Model=setModel)
foo
}
testcode(t)
However I get segfaults whenever I try to access any of the variables
contained in Model. So my question is: am I doing something wrong here? Is
list the right data type to wrap a structure in? I cant see any
documentation about wrapping structs in R.
Also when I pass strings to C from R they dont seem to be passed at all? Is
this a problem with R or a problem with me and if so how do I fix it?
It is a problem in your C code. The .C interface doesn't know about the
C declaration of the Model structure; it can only pass things it knows
about. So your C function test() should have its header set to accept
what gets passed to it. In your case, that's a list, so your C function
receives an array of pointers to SEXP structures; not the easiest things
to work with. Most people using .C() pass in simple vectors (numeric,
integer, etc.), and use the .Call() interface if they really need R
internals.
Duncan Murdoch
Many Thanks in advance,
Nathan
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