printf(":: x%"UVxf" to ..."
[download]

Dave.

yes thanks...spot on. the macro woz working all the way, but just the format cropping let me down. (although I must have missed it with gdb.)

so...

  printf(":: x%" UVxf " to ...", SvUV($input), $1);
[download]

does the job.

and here with a code example showing a few ugly ways to cast back pointers to all sorts...:

%typemap(in) void (* cb)(void *) , void *data , void (cb)(void *){
  //if SvGETMAGIC($input) {}; 
  $1 = INT2PTR($1_ltype, SvUV($input));
  printf(":: x%" UVxf " to x%lx\n", SvUV($input), $1);

  {
    int ret = SWIG_ConvertFunctionPtr($input, (void**)(& $1), 0);
    printf(":: to x%lx\n", $1);
  }

  if(SvGMAGICAL($input)) mg_get($input);
  $1 =  DPTR2FPTR($1_ltype, SvUV($input));
  printf("::DPTR2FPTR x%lx to x%lx\n", SvIV($input), $1);
}
[download]

bot::add_idle_callback x7fc3ff9bc040 , x0  
:: x7fc3ff9bc040 to x7fc3ff9bc040
:: to x7fc3ff9bc040
::DPTR2FPTR x7fc3ff9bc040 to x7fc3ff9bc040
:: x0 to x0
:: to x0
::DPTR2FPTR x0 to x0
::in c  add_idle_callback xff9bc040 , x0
[download]

Tip:

You can replace

if(SvGMAGICAL($input)) mg_get($input);
[download]

with

SvGETMAGIC($input);
[download]

(Just spotted that in a cursory glance. Didn't look at the rest.)