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https://github.com/python/cpython.git
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Issue #17807: Generators can now be finalized even when they are part of a reference cycle.
This commit is contained in:
Antoine Pitrou
parent
070cb3c9be
commit
04e70d19e7
8 changed files with 335 additions and 245 deletions
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@ -31,6 +31,195 @@ frame_getlocals(PyFrameObject *f, void *closure)
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return f->f_locals;
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}
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/*
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* Generator support.
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*/
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PyObject *
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_PyFrame_YieldingFrom(PyFrameObject *f)
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{
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PyObject *yf = NULL;
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if (f && f->f_stacktop) {
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PyObject *bytecode = f->f_code->co_code;
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unsigned char *code = (unsigned char *)PyBytes_AS_STRING(bytecode);
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if (code[f->f_lasti + 1] != YIELD_FROM)
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return NULL;
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yf = f->f_stacktop[-1];
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Py_INCREF(yf);
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}
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return yf;
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}
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PyObject *
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_PyFrame_GeneratorSend(PyFrameObject *f, PyObject *arg, int exc)
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{
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PyThreadState *tstate = PyThreadState_GET();
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PyObject *result;
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PyGenObject *gen = (PyGenObject *) f->f_gen;
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assert(gen == NULL || PyGen_CheckExact(gen));
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if (gen && gen->gi_running) {
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PyErr_SetString(PyExc_ValueError,
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"generator already executing");
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return NULL;
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}
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if (f->f_stacktop == NULL) {
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/* Only set exception if send() called, not throw() or next() */
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if (arg && !exc)
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PyErr_SetNone(PyExc_StopIteration);
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return NULL;
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}
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if (f->f_lasti == -1) {
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if (arg && arg != Py_None) {
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PyErr_SetString(PyExc_TypeError,
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"can't send non-None value to a "
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"just-started generator");
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return NULL;
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}
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} else {
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/* Push arg onto the frame's value stack */
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result = arg ? arg : Py_None;
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Py_INCREF(result);
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*(f->f_stacktop++) = result;
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}
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/* Generators always return to their most recent caller, not
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* necessarily their creator. */
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Py_XINCREF(tstate->frame);
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assert(f->f_back == NULL);
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f->f_back = tstate->frame;
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if (gen) {
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Py_INCREF(gen);
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gen->gi_running = 1;
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}
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result = PyEval_EvalFrameEx(f, exc);
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if (gen) {
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gen->gi_running = 0;
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/* In case running the frame has lost all external references
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* to gen, we must be careful not to hold on an invalid object. */
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if (Py_REFCNT(gen) == 1)
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Py_CLEAR(gen);
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else
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Py_DECREF(gen);
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}
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/* Don't keep the reference to f_back any longer than necessary. It
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* may keep a chain of frames alive or it could create a reference
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* cycle. */
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assert(f->f_back == tstate->frame);
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Py_CLEAR(f->f_back);
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/* If the generator just returned (as opposed to yielding), signal
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* that the generator is exhausted. */
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if (result && f->f_stacktop == NULL) {
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if (result == Py_None) {
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/* Delay exception instantiation if we can */
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PyErr_SetNone(PyExc_StopIteration);
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} else {
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PyObject *e = PyObject_CallFunctionObjArgs(
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PyExc_StopIteration, result, NULL);
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if (e != NULL) {
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PyErr_SetObject(PyExc_StopIteration, e);
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Py_DECREF(e);
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}
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}
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Py_CLEAR(result);
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}
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if (f->f_stacktop == NULL) {
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/* generator can't be rerun, so release the frame */
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/* first clean reference cycle through stored exception traceback */
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PyObject *t, *v, *tb;
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t = f->f_exc_type;
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v = f->f_exc_value;
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tb = f->f_exc_traceback;
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f->f_exc_type = NULL;
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f->f_exc_value = NULL;
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f->f_exc_traceback = NULL;
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Py_XDECREF(t);
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Py_XDECREF(v);
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Py_XDECREF(tb);
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if (gen) {
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f->f_gen = NULL;
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Py_CLEAR(gen->gi_frame);
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}
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}
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return result;
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}
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int
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_PyFrame_CloseIterator(PyObject *yf)
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{
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PyObject *retval = NULL;
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_Py_IDENTIFIER(close);
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if (PyGen_CheckExact(yf)) {
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PyFrameObject *f = ((PyGenObject *) yf)->gi_frame;
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assert(f != NULL);
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retval = _PyFrame_Finalize(f);
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if (retval == NULL)
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return -1;
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} else {
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PyObject *meth = _PyObject_GetAttrId(yf, &PyId_close);
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if (meth == NULL) {
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if (!PyErr_ExceptionMatches(PyExc_AttributeError))
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PyErr_WriteUnraisable(yf);
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PyErr_Clear();
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} else {
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retval = PyObject_CallFunction(meth, "");
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Py_DECREF(meth);
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if (retval == NULL)
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return -1;
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}
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}
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Py_XDECREF(retval);
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return 0;
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}
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PyObject *
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_PyFrame_Finalize(PyFrameObject *f)
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{
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int err = 0;
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PyObject *retval;
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PyGenObject *gen = (PyGenObject *) f->f_gen;
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PyObject *yf = _PyFrame_YieldingFrom(f);
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assert(gen == NULL || PyGen_CheckExact(gen));
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if (yf) {
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if (gen)
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gen->gi_running = 1;
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err = _PyFrame_CloseIterator(yf);
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if (gen)
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gen->gi_running = 0;
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Py_DECREF(yf);
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}
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if (err == 0)
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PyErr_SetNone(PyExc_GeneratorExit);
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retval = _PyFrame_GeneratorSend(f, Py_None, 1);
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if (retval) {
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Py_DECREF(retval);
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PyErr_SetString(PyExc_RuntimeError,
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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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PyErr_Clear(); /* ignore these errors */
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Py_INCREF(Py_None);
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return Py_None;
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}
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return NULL;
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}
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/*
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* Line number support.
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*/
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int
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PyFrame_GetLineNumber(PyFrameObject *f)
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{
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@ -419,33 +608,44 @@ static int numfree = 0; /* number of frames currently in free_list */
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/* max value for numfree */
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#define PyFrame_MAXFREELIST 200
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static void
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frame_clear(PyFrameObject *f);
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static void
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frame_dealloc(PyFrameObject *f)
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{
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PyObject **p, **valuestack;
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PyCodeObject *co;
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Py_REFCNT(f)++;
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frame_clear(f);
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Py_REFCNT(f)--;
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if (Py_REFCNT(f) > 0) {
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/* Frame resurrected! */
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Py_ssize_t refcnt = Py_REFCNT(f);
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_Py_NewReference((PyObject *) f);
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Py_REFCNT(f) = refcnt;
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/* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
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* we need to undo that. */
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_Py_DEC_REFTOTAL;
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/* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
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* chain, so no more to do there.
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* If COUNT_ALLOCS, the original decref bumped tp_frees, and
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* _Py_NewReference bumped tp_allocs: both of those need to be
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* undone.
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*/
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#ifdef COUNT_ALLOCS
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--(Py_TYPE(self)->tp_frees);
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--(Py_TYPE(self)->tp_allocs);
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#endif
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}
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PyObject_GC_UnTrack(f);
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Py_TRASHCAN_SAFE_BEGIN(f)
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/* Kill all local variables */
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valuestack = f->f_valuestack;
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for (p = f->f_localsplus; p < valuestack; p++)
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Py_CLEAR(*p);
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/* Free stack */
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if (f->f_stacktop != NULL) {
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for (p = valuestack; p < f->f_stacktop; p++)
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Py_XDECREF(*p);
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}
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Py_XDECREF(f->f_back);
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Py_DECREF(f->f_builtins);
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Py_DECREF(f->f_globals);
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Py_CLEAR(f->f_locals);
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Py_CLEAR(f->f_trace);
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Py_CLEAR(f->f_exc_type);
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Py_CLEAR(f->f_exc_value);
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Py_CLEAR(f->f_exc_traceback);
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co = f->f_code;
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if (co->co_zombieframe == NULL)
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@ -497,12 +697,25 @@ frame_clear(PyFrameObject *f)
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{
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PyObject **fastlocals, **p, **oldtop;
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Py_ssize_t i, slots;
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PyObject *retval;
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/* Before anything else, make sure that this frame is clearly marked
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* as being defunct! Else, e.g., a generator reachable from this
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* frame may also point to this frame, believe itself to still be
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* active, and try cleaning up this frame again.
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*/
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if (f->f_back == NULL) {
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PyObject *t, *v, *tb;
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PyErr_Fetch(&t, &v, &tb);
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/* Note that this can finalize a suspended generator frame even
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* if the generator object was disposed of (i.e. if f_gen is NULL).
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*/
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retval = _PyFrame_Finalize(f);
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if (retval == NULL) {
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if (PyErr_Occurred())
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PyErr_WriteUnraisable((PyObject *) f);
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}
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else
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Py_DECREF(retval);
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PyErr_Restore(t, v, tb);
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}
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/* Make sure the frame is now clearly marked as being defunct */
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oldtop = f->f_stacktop;
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f->f_stacktop = NULL;
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@ -713,6 +926,7 @@ PyFrame_New(PyThreadState *tstate, PyCodeObject *code, PyObject *globals,
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f->f_lasti = -1;
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f->f_lineno = code->co_firstlineno;
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f->f_iblock = 0;
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f->f_gen = NULL;
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_PyObject_GC_TRACK(f);
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return f;
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