[Insight-developers] Swig Wrapping Warnings.

[William A. Hoffman]

Since swig is a moving target, and we do updates from time to time, it may
be best to try and turn off warning checking for the generated code.  The
code is either correct or it is not, fixing warnings is not really a productive
exercise for swig generated wrappers.  Many times the problems show
up because C++ use const much more than C, swig generated code usually has
to be able to be compiled by an ANSI C compiler, and many of the warning fixes
break in C, but work in C++.

-Bill


At 11:33 AM 4/5/2004, Hans J. Johnson wrote:
>Hello Wrapping Experts,
>
>I've been attempting to get rid of compiler warnings from CableSwig tcl
>wrapped code.  The first set of changes were relativly easy to make, and
>eliminated about 7000 warnings.  Unfortunatly there are still about 5000
>warnings left to go.
>
>I beleive that one fix in cable swig will get rid of them, but I've been
>unable to successfully figure out how to do it.  The problem is that
>Swig chops off all const qualifiers for any local variable that will be
>an lvalue.  This is OK for non-pointer (non-reference) types, because
>the behavior does not affect the safety of the code, or it's use.  This,
>however, is not the case for pointers where the const is specified
>before the '*'.  
>
>e.g.
>===================================================================================================================
>static int
>_wrap_itkLightObject_GetNameOfClass(ClientData clientData, Tcl_Interp *interp, int objc, Tcl_Obj *CONST objv[]) {
>    (void)clientData; (void)interp; (void)objc; (void)objv;
>    itk::LightObject *arg1 = (itk::LightObject *) 0 ;
>    char *result;
>
>    if (SWIG_GetArgs(interp, objc, objv,"o:itkLightObject_GetNameOfClass self ",0) == TCL_ERROR) SWIG_fail;
>    if ((SWIG_ConvertPtr(objv[1], (void **) &arg1, SWIGTYPE_p_itk__LightObject,SWIG_POINTER_EXCEPTION | 0) != TCL_OK)) SWIG_fail;
>    try {
>        result = (char *)((itk::LightObject const *)arg1)->GetNameOfClass();
>    }
>    catch(std::exception &_e) {
>        {
>            SWIG_exception(SWIG_RuntimeError, const_cast<char*>(_e.what()));
>        }
>    }
>    Tcl_SetObjResult(interp,Tcl_NewStringObj(result,-1));
>    return TCL_OK;
>    fail:
>    return TCL_ERROR;
>}
>===================================================================================================================
>Two changes could remove the compiler warnings in the previous code snip are: 
>(a) change the type of result to "const char * reusult;" and change/remove the type casting in the try block.
>(b) use a const_cast<char *>() in the try block instead of the c-style (char *)---(const char *) may also work.
>
>I've spent a few days trying to learn the swig wrapping mechanism well enough to make these changes, but have not
>found a complete working solution and have not been confident that the partial solutions would not break other 
>wrappings.  A patch that does the first 1/2 of option (a) is attached to this e-mail.  I could not track down where
>the second part was being constucted.
>
>I will not be able to devote any more time to this.
>
>Sorry,
>Hans J. Johnson
>hans-johnson at uiowa.edu
>
>
>