Thanks, But it still is a mystery... By using "int & " instead of "int *", the C-code looks alright and the C-function is called with the right parameters. But the value that the C-funtion writes to the int pointers are not passed back to perl.

Example in the generated C-file:

XS_EUPXS(XS_TellStick_tdSensor); /* prototype to pass -Wmissing-protot
+ypes */
XS_EUPXS(XS_TellStick_tdSensor)
{
  dVAR; dXSARGS;
  if (items != 6)
    croak_xs_usage(cv,  "protocol, protocolLen, model, modelLen, id, d
+ataTypes");
  {
    char *  protocol = (char *)SvPV_nolen(ST(0))
;
    int     protocolLen = (int)SvIV(ST(1))
;
    char *  model = (char *)SvPV_nolen(ST(2))
;
    int     modelLen = (int)SvIV(ST(3))
;
    int     id = (int)SvIV(ST(4))
;
    int     dataTypes = (int)SvIV(ST(5))
;
    int     RETVAL;
    dXSTARG;

    printf("id1: %d\n", id);
    RETVAL = tdSensor(protocol, protocolLen, model, modelLen, &id, &da
+taTypes);
    printf("id2: %d\n", id);
    XSprePUSH; PUSHi((IV)RETVAL);
  }
  XSRETURN(1);
}
[download]

I added two printf for debugging (best debug tool...) and when I run it with like this:

...
my $sensorId = 1;
TellStick::tdSensor($protocol, 25, $model, 25, $sensorId, $dataTypes);
 print "protocol: $protocol, model: $model, sensorId: $sensorId, dataT
+ypes: $dataTypes\n";

I get the output

id1: 1
id2: 51
protocol: mandolyn, model: temperaturehumidity, sensorId: 1, dataTypes
+: 2
[download]

So it gets the correct value (51), but that is not passed back.

It looks like the XS code only sees the id parameter as an input value (casting it right), but no output is generated (except the return value). The string arguments (protocol, model), seems to work in modifying what the value is pointing to.

Should I somehow use "int *" in the XS anyway, but writing some special code for INPUT/OUTPUT in the typemap? Or is there some other way of returing the correct value?

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