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Crash - cause 'memory not mapped'

6 messages · niandra, gianluca mastrantonio, Dirk Eddelbuettel +2 more

Original
niandra
# 
i'm using the following  c++ code
using namespace std;
#include <iostream>
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv/highgui.h>
#include <opencv/cv.h> 
#include <R.h>
#include <Rinternals.h>
#include <Rmath.h>

extern "C" {
SEXP FiltroGaus(SEXP size1_r, SEXP size2_r, SEXP sigma_r) {

    int size1 = INTEGER(size1_r)[0];
    int size2 = INTEGER(size2_r)[0];
    double sigma = REAL(sigma_r)[0];
   
}
}

The compilation go without errors but when in R i type 
.C("FiltroGaus",3,3,2)
the message is:  Errore: INTEGER() can only be applied to a 'integer', not a
'NULL'
if i type .C("FiltroGaus",as.integer(3),as.integer(3),as.double(2))
the message is Errore: INTEGER() can only be applied to a 'integer', not a
'closure'

while if i type .Call("FiltroGaus",as.integer(3),as.integer(3),as.double(2))
the message is 
NULL

 *** caught segfault ***
address 0x200000be, cause 'memory not mapped'

Possible actions:
1: abort (with core dump, if enabled)
2: normal R exit
3: exit R without saving workspace
4: exit R saving workspace


I now, i need to study and i know also for sure the answer is in some book
(i have  lot). I swear i read a lot and i'm still reading, but i really need
help :)



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Peter Langfelder
# 
I'm not an expert, but from what I know you should certainly use the
.Call interface when you define a function as you did. The problem is
that your function must return a value (of type SEXP) which it does
not. If you don't return a value, all bets are off as to what will
happen, and if the internal R code uses a pointer to the result of
your function, you can easily get memory map errors.

HTH,

Peter
On Fri, Nov 9, 2012 at 2:31 PM, niandra <gianluca.mastrantonio at yahoo.it> wrote:
gianluca mastrantonio
# 
the error "memory non mapped" happen also if i use
void FiltroGaus(SEXP size1_r, SEXP size2_r, SEXP sigma_r) 
instead
SEXP FiltroGaus(SEXP size1_r, SEXP size2_r, SEXP sigma_r) {


Il giorno 09/nov/2012, alle ore 23:58, Peter Langfelder <peter.langfelder at gmail.com> ha scritto:
Dirk Eddelbuettel
#
On 9 November 2012 at 14:31, niandra wrote:
| extern "C" {
| SEXP FiltroGaus(SEXP size1_r, SEXP size2_r, SEXP sigma_r) {

[...]
 
| The compilation go without errors but when in R i type 
| .C("FiltroGaus",3,3,2)

You missed the part in "Writing R Extension" about .C() and .Call()
arguments.  You are mixing both approaches here, which usually ends badly.

Do some more reading, and maybe study some existing (simpler) examples /
packages.  You really do not need to engage OpenCV headers and libraries
before you understand the basics better.  

Dirk
Peter Langfelder
# 
On Fri, Nov 9, 2012 at 3:05 PM, gianluca mastrantonio
<gianluca.mastrantonio at yahoo.it> wrote:
If you use a .Call on a function, the function must return a SEXP, it
cannot be have a void return value.

Peter
2 days later