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bpo-1621: Avoid signed integer overflow in set_table_resize(). (GH-9059) 

Address a C undefined behavior signed integer overflow issue in set object table resizing.  Our -fwrapv compiler flag and practical reasons why sets are unlikely to get this large should mean this was never an issue but it was incorrect code that generates code analysis warnings.

<!-- issue-number: [bpo-1621](https://www.bugs.python.org/issue1621) -->
https://bugs.python.org/issue1621
<!-- /issue-number -->
This commit is contained in:
Sergey Fedoseev 2018-09-12 04:18:01 +05:00 committed by Miss Islington (bot)
parent 4859ba0d2c
commit 6c7d67ce83
2 changed files with 5 additions and 8 deletions
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2
Misc/NEWS.d/next/Core and Builtins/2018-09-11-15-19-37.bpo-1621.7o19yG.rst Normal file
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@ -0,0 +1,2 @@
Do not assume signed integer overflow behavior (C undefined behavior) when
performing set hash table resizing.

11
Objects/setobject.c
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@ -302,7 +302,6 @@ actually be smaller than the old one.
static int
set_table_resize(PySetObject *so, Py_ssize_t minused)
{
Py_ssize_t newsize;
setentry *oldtable, *newtable, *entry;
Py_ssize_t oldmask = so->mask;
size_t newmask;
@ -313,13 +312,9 @@ set_table_resize(PySetObject *so, Py_ssize_t minused)
/* Find the smallest table size > minused. */
/* XXX speed-up with intrinsics */
for (newsize = PySet_MINSIZE;
newsize <= minused && newsize > 0;
newsize <<= 1)
;
if (newsize <= 0) {
PyErr_NoMemory();
return -1;
size_t newsize = PySet_MINSIZE;
while (newsize <= (size_t)minused) {
newsize <<= 1; // The largest possible value is PY_SSIZE_T_MAX + 1.
}
/* Get space for a new table. */