ImageTk int overflow error

[vlachoudis]

I am running on a 32bit Fedora-23 virtual machine via virtualbox, version 3.0.0-4
When I try to convert an image to tkimage I get an overflow error
since the tk.interpaddr() returns a 64bit address which cannot be converted to int.

The same code in 64bit Fedora-23 save version works ok.

File "/usr/local/flair/lib/ZoomImage.py", line 162, in zoomImage
    self.tkimage = ImageTk.PhotoImage(self.photo)
  File "/usr/lib/python2.7/site-packages/PIL/ImageTk.py", line 115, in __init__
    self.paste(image)
  File "/usr/lib/python2.7/site-packages/PIL/ImageTk.py", line 182, in paste
    _imagingtk.tkinit(tk.interpaddr(), 1)
OverflowError: Python int too large to convert to C long

>>> from Tkinter import *
>>> tk=Tk()
>>> tk.interpaddr()
2161299816L

[wiredfool]

It's not actually a 64 bit address, but it is in the upper 2gb of a 32 bit address. Which is too big to fit into a Py_ssize_t on 32 bit, which is limited to 2^31.

The value is actually a PyInt_FromLong, from _tkinter.c:

static PyObject *
Tkapp_InterpAddr(PyObject *self, PyObject *args)
{

    if (!PyArg_ParseTuple(args, ":interpaddr"))
        return NULL;

    return PyInt_FromLong((long)Tkapp_Interp(self));
}

Which is interpreted as a an int->Py_ssize_t in _imagingtk.c

static PyObject*
_tkinit(PyObject* self, PyObject* args)
{
    Tcl_Interp* interp;

    Py_ssize_t arg;
    int is_interp;
    if (!PyArg_ParseTuple(args, "ni", &arg, &is_interp))
        return NULL;

    if (is_interp)
        interp = (Tcl_Interp*) arg;
    else {
        TkappObject* app;
    /* Do it the hard way.  This will break if the TkappObject
       layout changes */
        app = (TkappObject*) arg;
        interp = app->interp;
    }

Given the evidence here, I don't think that it's actually possible to reliably (in all cases, with all corners of 32/64 signed/unsigned silliness) pass a pointer through as an interpreted int. It can be passed as a PyInt, and then it needs to be interpreted as something like:

    void *arg;
    PyObject *int_obj;
    if (!PyArg_ParseTuple(args, "Oi", &int_obj, &is_interp)){
        return NULL;
    }

    if (PyInt_Check(int_obj)) {
        if (sizeof(arg) == 4) {
            arg =  PyInt_AsUnsignedLongMask(int_obj); 
        } elseif (sizeof(arg) == 8) {
            arg =  PyInt_AsUnsignedLongLongMask(int_obj);
        } else {
            // barf loudly?
            return NULL;
        }
     } else {
         // set error here
        return NULL;
     }

[wiredfool]

from the debian bug report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847812

matplotlib/matplotlib@a91559b

[vlachoudis]

I had a similar issue in one program of mine, and I solve it by changing the ParseTuple as

	unsigned long interpaddr;
...
	if (!PyArg_ParseTuple(args, "Osk", &geometry, &winname, &interpaddr)) return -1;
        Tcl_Interp *interp = (Tcl_Interp*)interpaddr;

and it works nicely in both 32bit and 64bit environments.

[wiredfool]

I don't think that is valid in a 64 bit environment because a pointer doesn't fit into an unsigned long.