[Python-Dev] Adding support to curses library

[Heracles]

I took the suggestion and fired up a debugger and now I'm eating crow.

First of all, here is a complete listing of the method as it is written now:
------------------   Snippet -----------------------------------
static PyObject *
PyCurses_color_set(PyObject *self, PyObject *args)
{
   short color_pair_number = 0;
   void * opts = NULL;
   int erg = ERR;

   /* These macros ought to be documented in the API docs
       but they aren't yet. */
   PyCursesInitialised
   PyCursesInitialisedColor

   /* Per ncurses Man Page: 
       The routine color_set sets the current color of the given window to
       the foreground/background combination described by the
color_pair_number. 
       The parameter opts is reserved for future use, applications must
supply a 
        null pointer. */
   switch(PyTuple_Size(args))
   {
   case 1:
	   /* Dont make them pass a useless null pointer. */
	   if (!PyArg_ParseTuple(args, "h", &color_pair_number)) return NULL;
   case 2:
	   /* Allow them to pass the opts pointer so that when ncurses is later
updated.
	       This method will still work. */
	   if (!PyArg_ParseTuple(args, "hO&", &color_pair_number, &opts)) return
NULL;	
   default:
      PyErr_SetString(PyExc_TypeError, "color_set requires 1 or 2 arguments
(color_pair_number[, opts]?)");
	  return NULL;
   }

   erg = color_set(color_pair_number, NULL); 
   
   if (erg == ERR) 
      return PyCursesCheckERR(erg, "color_set");
   else 
      return NULL; /* PyInt_FromLong((long) 1L); */
}
------------------  End Snippet -------------------------------------

Oddly enough, running the debugger showed me a different result than I
expected by my bracketing approach.  I falsely presumed that if by
commenting out the line where the call to color_set is made, and running the
program produces no segmentation fault, while commenting the same line back
in reprduces the segmentation fault, that I could deduce that the line thus
commented out was the source of the problem.  Stupid me, that is apparently
not the case.

Apparently the segmentation fault is produced by a call to
Python/getargs.c:Line 1207
   if(! (*convert)(arg,addr))

Which is invoked as a result of calling this line in the function listed
above:
  if (!PyArg_ParseTuple(args, "hO&", &color_pair_number, &opts)) return
NULL;	





A.M. Kuchling wrote:
> 
> On Wed, Feb 25, 2009 at 06:30:06AM -0800, Heracles wrote:
>> is commented back in it does fail. I am not sure exactly how a debugger
>> will
>> help in this case since the color_set call goes directly to the ncurses
>> library.  If in fact that the issue is the ncurses library then it seems
>> that there is no feasible solution until that library is fixed, in which
>> case this patch is sort of useless.
> ...
>> erg = color_set(color_pair_number, NULL); // Debating on forcing null
> 
> What is color_pair_number in the C code?  If it's some incorrect value
> (-1?  255?), maybe ncurses is indexing off an array and crashing.  
> 
> This is why a debugger might help; you could run the test program
> until the crash and then print out the values of the relevant
> variables.  e.g. is stdscr set to a non-NULL value?  There might be a
> debugging version of ncurses that will let you look at the variables
> inside the ncurses code, which may make the problem clear.
> 
> --amk
> 
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:wistle::wistle::wistle:
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