New submission from martenjan:
The code for gc_list_merge is given in gcmodule.c. I retrieved it from
http://hg.python.org/cpython/file/tip/Modules/gcmodule.c#l287
The code seems to merge list `from` incompletely: the first entry of `from` is
omitted in the merged list.
The issue is in line 295: tail->gc.gc_next = from->gc.gc_next;
I fixed it as : tail->gc.gc_next = from;
Please check if my analysis is correct.
See below for the context.
Original: lines 287 to 301
/* append list `from` onto list `to`; `from` becomes an empty list */
static void
gc_list_merge(PyGC_Head *from, PyGC_Head *to)
{
PyGC_Head *tail;
assert(from != to);
if (!gc_list_is_empty(from)) {
tail = to->gc.gc_prev;
tail->gc.gc_next = from->gc.gc_next;
tail->gc.gc_next->gc.gc_prev = tail;
to->gc.gc_prev = from->gc.gc_prev;
to->gc.gc_prev->gc.gc_next = to;
}
gc_list_init(from);
}
Fix:
/* append list `from` onto list `to`; `from` becomes an empty list */
static void
gc_list_merge(PyGC_Head *from, PyGC_Head *to)
{
PyGC_Head *tail;
assert(from != to);
if (!gc_list_is_empty(from)) {
tail = to->gc.gc_prev;
tail->gc.gc_next = from;
tail->gc.gc_next->gc.gc_prev = tail;
to->gc.gc_prev = from->gc.gc_prev;
to->gc.gc_prev->gc.gc_next = to;
}
gc_list_init(from);
}
------
components: Interpreter Core
messages: 202206
nosy: martenjan
priority: normal
severity: normal
status: open
title: does gc_list_merge merge properly?
type: behavior
versions: Python 2.7
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<http://bugs.python.org/issue19503>
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