Fix SF#1470508: crash in generator cycle finalization. There were two
problems: first, PyGen_NeedsFinalizing() had an off-by-one bug that prevented it from ever saying a generator didn't need finalizing, and second, frame objects cleared themselves in a way that caused their owning generator to think they were still executable, causing a double deallocation of objects on the value stack if there was still a loop on the block stack. This revision also removes some unnecessary close() operations from test_generators that are now appropriately handled by the cycle collector.
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@ -421,7 +421,6 @@ Subject: Re: PEP 255: Simple Generators
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... self.name = name
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... self.parent = None
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... self.generator = self.generate()
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... self.close = self.generator.close
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...
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... def generate(self):
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... while not self.parent:
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@ -484,8 +483,6 @@ A->A B->G C->A D->G E->G F->A G->G H->G I->A J->G K->A L->A M->G
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merged A into G
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A->G B->G C->G D->G E->G F->G G->G H->G I->G J->G K->G L->G M->G
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>>> for s in sets: s.close() # break cycles
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"""
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# Emacs turd '
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@ -593,7 +590,6 @@ arguments are iterable -- a LazyList is the same as a generator to times().
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... def __init__(self, g):
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... self.sofar = []
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... self.fetch = g.next
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... self.close = g.close
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...
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... def __getitem__(self, i):
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... sofar, fetch = self.sofar, self.fetch
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@ -624,8 +620,6 @@ efficient.
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[200, 216, 225, 240, 243, 250, 256, 270, 288, 300, 320, 324, 360, 375, 384]
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[400, 405, 432, 450, 480, 486, 500, 512, 540, 576, 600, 625, 640, 648, 675]
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>>> m235.close()
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Ye olde Fibonacci generator, LazyList style.
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>>> def fibgen(a, b):
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@ -648,7 +642,6 @@ Ye olde Fibonacci generator, LazyList style.
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>>> fib = LazyList(fibgen(1, 2))
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>>> firstn(iter(fib), 17)
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[1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584]
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>>> fib.close()
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Running after your tail with itertools.tee (new in version 2.4)
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@ -454,9 +454,15 @@ frame_traverse(PyFrameObject *f, visitproc visit, void *arg)
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static void
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frame_clear(PyFrameObject *f)
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{
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PyObject **fastlocals, **p;
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PyObject **fastlocals, **p, **oldtop;
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int i, slots;
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oldtop = f->f_stacktop;
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/* Before anything else, make sure that this frame is clearly marked
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as being defunct! */
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f->f_stacktop = NULL;
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Py_XDECREF(f->f_exc_type);
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f->f_exc_type = NULL;
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@ -473,17 +479,13 @@ frame_clear(PyFrameObject *f)
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slots = f->f_nlocals + f->f_ncells + f->f_nfreevars;
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fastlocals = f->f_localsplus;
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for (i = slots; --i >= 0; ++fastlocals) {
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if (*fastlocals != NULL) {
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Py_XDECREF(*fastlocals);
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*fastlocals = NULL;
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}
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Py_CLEAR(*fastlocals);
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}
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/* stack */
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if (f->f_stacktop != NULL) {
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for (p = f->f_valuestack; p < f->f_stacktop; p++) {
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Py_XDECREF(*p);
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*p = NULL;
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if (oldtop != NULL) {
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for (p = f->f_valuestack; p < oldtop; p++) {
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Py_CLEAR(*p);
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}
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}
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}
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@ -35,7 +35,7 @@ gen_dealloc(PyGenObject *gen)
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}
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_PyObject_GC_UNTRACK(self);
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Py_XDECREF(gen->gi_frame);
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Py_CLEAR(gen->gi_frame);
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PyObject_GC_Del(gen);
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}
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@ -130,8 +130,8 @@ gen_close(PyGenObject *gen, PyObject *args)
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"generator ignored GeneratorExit");
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return NULL;
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}
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if ( PyErr_ExceptionMatches(PyExc_StopIteration)
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|| PyErr_ExceptionMatches(PyExc_GeneratorExit) )
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if ( PyErr_ExceptionMatches(PyExc_StopIteration)
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|| PyErr_ExceptionMatches(PyExc_GeneratorExit) )
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{
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PyErr_Clear(); /* ignore these errors */
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Py_INCREF(Py_None);
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@ -208,7 +208,7 @@ PyDoc_STRVAR(throw_doc,
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return next yielded value or raise StopIteration.");
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static PyObject *
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gen_throw(PyGenObject *gen, PyObject *args)
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gen_throw(PyGenObject *gen, PyObject *args)
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{
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PyObject *typ;
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PyObject *tb = NULL;
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@ -328,7 +328,7 @@ PyTypeObject PyGen_Type = {
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0, /* tp_getset */
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0, /* tp_base */
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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0, /* tp_dictoffset */
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@ -366,15 +366,16 @@ PyGen_NeedsFinalizing(PyGenObject *gen)
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int i;
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PyFrameObject *f = gen->gi_frame;
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if (f == NULL || f->f_stacktop==NULL || f->f_iblock<=0)
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return 0; /* no frame or no blockstack == no finalization */
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if (f == NULL || f->f_stacktop == NULL || f->f_iblock <= 0)
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return 0; /* no frame or empty blockstack == no finalization */
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for (i=f->f_iblock; i>=0; i--) {
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/* Any block type besides a loop requires cleanup. */
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i = f->f_iblock;
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while (--i >= 0) {
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if (f->f_blockstack[i].b_type != SETUP_LOOP)
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/* any block type besides a loop requires cleanup */
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return 1;
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}
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/* No blocks except loops, it's safe to skip finalization */
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/* No blocks except loops, it's safe to skip finalization. */
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return 0;
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}
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