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visit_reachable: replace release-mode test with an assert. (GH-16866)

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It should be impossible for an untracked object to have the collecting
flag set.  Back when state was stored in gc_refs, it obviously was
impossible (gc_refs couldn't possibly have a positive & negative value
simultaneously).  While the _implementation_ of "state" has gotten much
more complicated, it's still _logically_ just as impossible.
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Tim Peters 2019-10-21 11:21:35 -05:00 • committed by GitHub
parent 5bc6a7c06e
commit 1e73945470
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1 changed files with 5 additions and 2 deletions
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7
Modules/gcmodule.c
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@ -468,13 +468,16 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
PyGC_Head *gc = AS_GC(op);
const Py_ssize_t gc_refs = gc_get_refs(gc);
// Ignore untracked objects and objects in other generation.
// Ignore objects in other generation.
// This also skips objects "to the left" of the current position in
// move_unreachable's scan of the 'young' list - they've already been
// traversed, and no longer have the PREV_MASK_COLLECTING flag.
if (gc->_gc_next == 0 || !gc_is_collecting(gc)) {
if (! gc_is_collecting(gc)) {
return 0;
}
// It would be a logic error elsewhere if the collecting flag were set on
// an untracked object.
assert(gc->_gc_next != 0);
if (gc->_gc_next & NEXT_MASK_UNREACHABLE) {
/* This had gc_refs = 0 when move_unreachable got