Hi Guido, When a user does the following with standard Python: tup = () for i in xrange(100000): tup = (tup, i) del tup # ka-boom He will get a core dump due to stack limitations. Recently, I changed Stackless Python to be safe for any recursive object built from lists, tuples, dictionaries, tracebacks and frames. The implementation is not Stackless Python dependant and very efficient (for my eyes at least). For efficiency, locality and minimum changes to five modules, it is implemented as two embracing macroes which are stuffed around the bodies of the deallocator methods, that makes just 3-4 lines of change for every module. (Well, the macro *can* be expanded if you like that more) I can submit patches, but please have a look at the example below, to save me the time in case you don't like it. It works great for SLP. cheers - chris -------------------------------------- Example of modified list deallocator: /* Methods */ static void list_dealloc(op) PyListObject *op; { int i; Py_TRASHCAN_SAFE_BEGIN(op) if (op->ob_item != NULL) { /* Do it backwards, for Christian Tismer. There's a simple test case where somehow this reduces thrashing when a *very* large list is created and immediately deleted. */ i = op->ob_size; while (--i >= 0) { Py_XDECREF(op->ob_item[i]); } free((ANY *)op->ob_item); } free((ANY *)op); Py_TRASHCAN_SAFE_END(op) } This is the original 1.5.2+ code, with two macro lines added. -------------------------------------- Here the macro code (which may of course be expanded) #define PyTrash_UNWIND_LEVEL 50 #define Py_TRASHCAN_SAFE_BEGIN(op) \ { \ ++_PyTrash_delete_nesting; \ if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \ #define Py_TRASHCAN_SAFE_END(op) \ ;} \ else { \ if (!_PyTrash_delete_later) \ _PyTrash_delete_later = PyList_New(0); \ if (_PyTrash_delete_later) \ PyList_Append(_PyTrash_delete_later, (PyObject *)op); \ } \ --_PyTrash_delete_nesting; \ while (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) { \ PyObject *shredder = _PyTrash_delete_later; \ _PyTrash_delete_later = NULL; \ ++_PyTrash_delete_nesting; \ Py_DECREF(shredder); \ --_PyTrash_delete_nesting; \ } \ } \ extern DL_IMPORT(int) _PyTrash_delete_nesting; extern DL_IMPORT(PyObject *) _PyTrash_delete_later; -- Christian Tismer :^) mailto:tismer@appliedbiometrics.com Applied Biometrics GmbH : Have a break! Take a ride on Python's Kaunstr. 26 : *Starship* http://starship.python.net 14163 Berlin : PGP key -> http://wwwkeys.pgp.net PGP Fingerprint E182 71C7 1A9D 66E9 9D15 D3CC D4D7 93E2 1FAE F6DF we're tired of banana software - shipped green, ripens at home