Re: [Swig-user] Java: Unable to remove a wrongly generated line

[William S F. <ws...@fu...>]

Sylvestre Ledru wrote:
> Hello,
> 
> I am trying to map in Java the following line:
> int putDouble(char * variableName, double variable[], int nbRow, int
> nbCol);
> to
>   public final static native int putDouble(String jarg1, double[][]
> jarg2);
> 
> I have been able to manage the input arguments but I am stuck by a line
> added by SWIG.
> After the native call on putDouble, SWIG is adding the following line:
>   SWIG_JavaArrayArgoutDouble(jenv, jarr2, arg2, jarg2);
> I really don't see why this line is added by SWIG and all my tries to
> remove it failed.
> How can I get ride of this line ?
> 
> My .i file is the following:
> 
> %include "arrays_java.i"
> 
> /* Transform the input datatype double[] to double[][] to facilitate
> the 
> matching in Java */
> %typemap(jni) double[] "jobjectArray"
> %typemap(jtype) double[] "double[][]"
> %typemap(jstype) double[] "double[][]"
> 
> %typemap(in) (double variable[], int nbRow, int nbCol) {
> // Convert the double[][] => double *
> [...]
> }
> 
> int putDouble(char * variableName, double variable[], int nbRow, int
> nbCol);
> 

You can analyse which typemaps are contributing code by using the 
-debug-tmused option to SWIG. If you grep the output for the variable 
name you are interested in you get:

$ swig -java -c++ -debug-tmused example.i | grep -w variable
example.i:9: Typemap for double variable[] (jni) : %typemap(jni) double []
example.i:9: Typemap for double variable[] (jtype) : %typemap(jtype) 
double []
example.i:9: Typemap for double variable[] (jstype) : %typemap(jstype) 
double []
example.i:9: Typemap for double variable[] (in) : %typemap(in) (double 
variable[],int nbRow,int nbCol)
example.i:9: Typemap for double variable[] (typecheck) : 
%typemap(typecheck) double []
example.i:9: Typemap for double variable[] (argout) : %typemap(argout) 
double []
example.i:9: Typemap for double variable[] (freearg) : %typemap(freearg) 
double []
example.i:9: Typemap for double variable[] (jstype) : %typemap(jstype) 
double []
example.i:9: Typemap for double variable[] (javain) : %typemap(javain) 
double []


These show the typemaps that are being used for wrapping variable[], so 
one of these will contribute the SWIG_JavaArrayArgoutDouble code. If you 
look at each of these typemaps (you can use swig -E to see the 
preprocessed output) or just guess that the argout typemap is the 
source. As you are using an 'in' multi-argument typemap, you need to 
provide your own 'argout' multi-argument typemap:

%typemap(argout) (double variable[], int nbRow, int nbCol) {
... code to marshal array elements from C++ to Java ...
}

Interestingly the 'freearg' typemap is silently ignored because it does 
not match the 'in' typemap (they are not both multi-argument typemaps). 
One could argue that the 'argout' typemap should be treated the same, 
but I'll probably just add a warning that the 'in' does not match 'freearg'.

William