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[3.6] bpo-30416: Protect the optimizer during constant folding. (#4865)

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It no longer spends much time doing complex calculations and no
longer consumes much memory for creating large constants that will
be dropped later.

This fixes also bpo-21074.
This commit is contained in:
Serhiy Storchaka 2017-12-15 14:12:14 +02:00 • committed by GitHub
parent b82da9ebb2
commit b580f4f2bf
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 144 additions and 17 deletions
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3
Lib/test/test_memoryio.py
View file

@ -733,7 +733,8 @@ class CBytesIOTest(PyBytesIOTest):
check = self.check_sizeof
self.assertEqual(object.__sizeof__(io.BytesIO()), basesize)
check(io.BytesIO(), basesize )
check(io.BytesIO(b'a' * 1000), basesize + sys.getsizeof(b'a' * 1000))
n = 1000 # use a variable to prevent constant folding
check(io.BytesIO(b'a' * n), basesize + sys.getsizeof(b'a' * n))
# Various tests of copy-on-write behaviour for BytesIO.

9
Lib/test/test_peepholer.py
View file

@ -178,8 +178,15 @@ class TestTranforms(BytecodeTestCase):
self.assertInBytecode(code, 'LOAD_CONST', 'b')
# Verify that large sequences do not result from folding
code = compile('a="x"*1000', '', 'single')
code = compile('a="x"*10000', '', 'single')
self.assertInBytecode(code, 'LOAD_CONST', 10000)
self.assertNotIn("x"*10000, code.co_consts)
code = compile('a=1<<1000', '', 'single')
self.assertInBytecode(code, 'LOAD_CONST', 1000)
self.assertNotIn(1<<1000, code.co_consts)
code = compile('a=2**1000', '', 'single')
self.assertInBytecode(code, 'LOAD_CONST', 1000)
self.assertNotIn(2**1000, code.co_consts)
def test_binary_subscr_on_unicode(self):
# valid code get optimized

3
Misc/NEWS.d/next/Core and Builtins/2017-12-14-11-48-19.bpo-30416.hlHo_9.rst Normal file
View file

@ -0,0 +1,3 @@
The optimizer is now protected from spending much time doing complex
calculations and consuming much memory for creating large constants in
constant folding.

146
Python/peephole.c
View file

@ -167,6 +167,37 @@ copy_op_arg(_Py_CODEUNIT *codestr, Py_ssize_t i, unsigned char op,
return maxi - 1;
}
/* Check whether a collection doesn't containing too much items (including
subcollections). This protects from creating a constant that needs
too much time for calculating a hash.
"limit" is the maximal number of items.
Returns the negative number if the total number of items exceeds the
limit. Otherwise returns the limit minus the total number of items.
*/
static Py_ssize_t
check_complexity(PyObject *obj, Py_ssize_t limit)
{
if (PyTuple_Check(obj)) {
Py_ssize_t i;
limit -= PyTuple_GET_SIZE(obj);
for (i = 0; limit >= 0 && i < PyTuple_GET_SIZE(obj); i++) {
limit = check_complexity(PyTuple_GET_ITEM(obj, i), limit);
}
return limit;
}
else if (PyFrozenSet_Check(obj)) {
Py_ssize_t i = 0;
PyObject *item;
Py_hash_t hash;
limit -= PySet_GET_SIZE(obj);
while (limit >= 0 && _PySet_NextEntry(obj, &i, &item, &hash)) {
limit = check_complexity(item, limit);
}
}
return limit;
}
/* Replace LOAD_CONST c1, LOAD_CONST c2 ... LOAD_CONST cn, BUILD_TUPLE n
with LOAD_CONST (c1, c2, ... cn).
The consts table must still be in list form so that the
@ -218,6 +249,101 @@ fold_tuple_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
return copy_op_arg(codestr, c_start, LOAD_CONST, len_consts, opcode_end);
}
#define MAX_INT_SIZE 128 /* bits */
#define MAX_COLLECTION_SIZE 20 /* items */
#define MAX_STR_SIZE 20 /* characters */
#define MAX_TOTAL_ITEMS 1024 /* including nested collections */
static PyObject *
safe_multiply(PyObject *v, PyObject *w)
{
if (PyLong_Check(v) && PyLong_Check(w) && Py_SIZE(v) && Py_SIZE(w)) {
size_t vbits = _PyLong_NumBits(v);
size_t wbits = _PyLong_NumBits(w);
if (vbits == (size_t)-1 || wbits == (size_t)-1) {
return NULL;
}
if (vbits + wbits > MAX_INT_SIZE) {
return NULL;
}
}
else if (PyLong_Check(v) && (PyTuple_Check(w) || PyFrozenSet_Check(w))) {
Py_ssize_t size = PyTuple_Check(w) ? PyTuple_GET_SIZE(w) :
PySet_GET_SIZE(w);
if (size) {
long n = PyLong_AsLong(v);
if (n < 0 || n > MAX_COLLECTION_SIZE / size) {
return NULL;
}
if (n && check_complexity(w, MAX_TOTAL_ITEMS / n) < 0) {
return NULL;
}
}
}
else if (PyLong_Check(v) && (PyUnicode_Check(w) || PyBytes_Check(w))) {
Py_ssize_t size = PyUnicode_Check(w) ? PyUnicode_GET_LENGTH(w) :
PyBytes_GET_SIZE(w);
if (size) {
long n = PyLong_AsLong(v);
if (n < 0 || n > MAX_STR_SIZE / size) {
return NULL;
}
}
}
else if (PyLong_Check(w) &&
(PyTuple_Check(v) || PyFrozenSet_Check(v) ||
PyUnicode_Check(v) || PyBytes_Check(v)))
{
return safe_multiply(w, v);
}
return PyNumber_Multiply(v, w);
}
static PyObject *
safe_power(PyObject *v, PyObject *w)
{
if (PyLong_Check(v) && PyLong_Check(w) && Py_SIZE(v) && Py_SIZE(w) > 0) {
size_t vbits = _PyLong_NumBits(v);
size_t wbits = PyLong_AsSize_t(w);
if (vbits == (size_t)-1 || wbits == (size_t)-1) {
return NULL;
}
if (vbits > MAX_INT_SIZE / wbits) {
return NULL;
}
}
return PyNumber_Power(v, w, Py_None);
}
static PyObject *
safe_lshift(PyObject *v, PyObject *w)
{
if (PyLong_Check(v) && PyLong_Check(w) && Py_SIZE(v) && Py_SIZE(w)) {
size_t vbits = _PyLong_NumBits(v);
size_t wbits = PyLong_AsSize_t(w);
if (vbits == (size_t)-1 || wbits == (size_t)-1) {
return NULL;
}
if (wbits > MAX_INT_SIZE || vbits > MAX_INT_SIZE - wbits) {
return NULL;
}
}
return PyNumber_Lshift(v, w);
}
static PyObject *
safe_mod(PyObject *v, PyObject *w)
{
if (PyUnicode_Check(v) || PyBytes_Check(v)) {
return NULL;
}
return PyNumber_Remainder(v, w);
}
/* Replace LOAD_CONST c1, LOAD_CONST c2, BINOP
with LOAD_CONST binop(c1,c2)
The consts table must still be in list form so that the
@ -234,7 +360,7 @@ fold_binops_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
PyObject *consts, PyObject **objs)
{
PyObject *newconst, *v, *w;
Py_ssize_t len_consts, size;
Py_ssize_t len_consts;
/* Pre-conditions */
assert(PyList_CheckExact(consts));
@ -245,10 +371,10 @@ fold_binops_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
w = objs[1];
switch (opcode) {
case BINARY_POWER:
newconst = PyNumber_Power(v, w, Py_None);
newconst = safe_power(v, w);
break;
case BINARY_MULTIPLY:
newconst = PyNumber_Multiply(v, w);
newconst = safe_multiply(v, w);
break;
case BINARY_TRUE_DIVIDE:
newconst = PyNumber_TrueDivide(v, w);
@ -257,7 +383,7 @@ fold_binops_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
newconst = PyNumber_FloorDivide(v, w);
break;
case BINARY_MODULO:
newconst = PyNumber_Remainder(v, w);
newconst = safe_mod(v, w);
break;
case BINARY_ADD:
newconst = PyNumber_Add(v, w);
@ -269,7 +395,7 @@ fold_binops_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
newconst = PyObject_GetItem(v, w);
break;
case BINARY_LSHIFT:
newconst = PyNumber_Lshift(v, w);
newconst = safe_lshift(v, w);
break;
case BINARY_RSHIFT:
newconst = PyNumber_Rshift(v, w);
@ -296,16 +422,6 @@ fold_binops_on_constants(_Py_CODEUNIT *codestr, Py_ssize_t c_start,
}
return -1;
}
size = PyObject_Size(newconst);
if (size == -1) {
if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt)) {
return -1;
}
PyErr_Clear();
} else if (size > 20) {
Py_DECREF(newconst);
return -1;
}
/* Append folded constant into consts table */
if (PyList_Append(consts, newconst)) {