[Swig-dev] Core dump in SWIG 1.3.17 - (newbie)

Sharma K M writes:
 > I am a newbie to SWIG. Here is my problem:
 > 
 > What is the equivalent of -
 > 1. extern const xint8_t *<parameter> = "<value>"
 > and
 > 2. the corresponding "typemap" statement
 > in the following piece of code under SWIG1.3.17?
 > 
 > For your information, the following code used to work
 > properly under SWIG 1.1p5.
 > =============================
 > %typemap(python, out) xint8_t**
 > {
 >     xint32_t len=0;
 > 
 >     while($source[len]) len++;
 >     $target = PyList_New(len);
 > 
 >     for(xint32_t i=0;i<len;i++)
 >         PyList_SetItem($target, i, PyString_FromString($source[i]));
 > }
 > 
 > extern const xint8_t *pyBlack = "K";
 > extern const xint8_t *pyBlackLow = "KL";
 > extern const xint8_t *pyGreyScale = "Grey";
 > =============================
 > 
 > With the above codes, under SWIG 1.3.17, I could get
 > *_wrap.cxx file with the required C++ methods. But,
 > it does NOT generate any statements in the corresponding
 > python file. I was expecting the following lines in
 > the generated python file:
 > ---------------------
 > pyBlack = _module.pyBlack
 > pyBlackLow = _module.pyBlackLow
 > pyGreyScale = _module.pyGreyScale
 > ---------------------
 > 
 > Whereas the above lines exist with SWIG 1.1p5 generated
 > python files.
 > 

Well, a bunch of things are happening here.  First, a declaration of
the form:

   extern const xint8_t *pyBlack = "K";

doesn't define a constant.  The reason it doesn't define a constant is 
that someone can redefine it's value.  For example:

   pyBlack = "Foo";

In other words---the pointer value can be changed to point to a
different location.   Therefore, this declaration is wrapped as a
global variable.  You would access it using:

   module.cvar.pyBlack

If you really want it to be a constant, use the %constant directive.

If xint8_t is the same as "char", you shouldn't need to write a
typemap.  Just use a typedef or say this:

   %apply char { xint8_t };

If you still want to write a typemap, you would use the "varout"
typemap for variables and the "consttab" typemap for constants.  To
see examples, look in Lib/python/python.swg.

Cheers,

Dave
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