Hi,
Perhaps you should try just passing in two integers to some toy C
function just to make sure all the plumbing is correct before you play
with strings/char arrays.
In any case, some comments inline:
On Aug 31, 2009, at 11:42 AM, naresh kumar wrote:
Hello Forum,
I'm calling C function from R.It is a
small sample trial
program. The C function will accept a string and a integer
and print them.
It is giving error segmentation fault.
Below are the C function, Wrapper code ,R code and
R
output.
Please help me in this issue
Thank you in
advance
Error:
*** caught segfault ***
address 0x68, cause 'memory not mapped'
Traceback:
1: .C("checkstr_R_wrapper", n = as.character(n), m =
as.integer(m), NAOK = TRUE, DUP = TRUE, result = integer(1))
2: checkstr("hi", 2)
Possible actions:
1: abort (with core dump, if enabled)
2: normal R exit
3: exit R without saving workspace
4: exit R saving workspace
Selection: 1
aborting ...
Segmentation fault
C FUNCTION (Name : checkstr.c)
#include<stdio.h>
#include<string.h>
int n_char(char n[10],int m)
{
int result;
result = 3;
result = strlen(n);
printf("the string is %s\n",n);
printf("the silly number is %d\n",m);
return result;
}
Why are you defining the first argument in this function as ``char
n[10]``. How do you know it's 10 chars long? My C is a bit rusty, but
I'm guessing this might be causing a problem (like a seg fault!) if
your n isn't 10 chars long.
WRAPPER CODE
(wrapcheckstr.c)
#include <stdio.h>
#include<string.h>
int n_char(char,int);
void checkstr_R_wrapper(char **n,int *m, int *result)
{ *result = n_char(**n,*m); }
[prod...@venus myrpackages]$
R CODE(checkstr.R)
source('checkstr.R')
checkstr <- function(n,m) {
if (!is.loaded(symbol.C('checkstr_R_wrapper')))
{ dyn.load('checkstr.so') }
returned_data = .C('checkstr_R_wrapper',
n=as.character(n),m=as.integer(m), result=integer(1))
return(returned_data$result) }
If you're going to be passing in arrays of anything (chars, ints,
etc), you should also pass in a sister variable that is the length of
the array itself.
So, your two functions might be:
void checkstr_R_wrapper(char **n, int n_length, int *m, int *result) {
*result = n_char(**n,*m);
}
and the R call would be:
.C('checkstr_R_wrapper',
n=as.character(n),
n_length=length(as.character(n)),
m=as.integer(m), result=integer(1))
... or something ... perhaps.
Does that help any?
-steve
--
Steve Lianoglou
Graduate Student: Computational Systems Biology
| Memorial Sloan-Kettering Cancer Center
| Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact
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