bpo-35091: Objects/listobject.c: Replace overflow checks in gallop fu… · python-emscripten/cpython@6bc5917 · GitHub

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Alexey Izbyshev

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miss-islington

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bpo-35091: Objects/listobject.c: Replace overflow checks in gallop fu… (pythonGH-10202)

…nctions with asserts The actual overflow can never happen because of the following: * The size of a list can't be greater than PY_SSIZE_T_MAX / sizeof(PyObject*). * The size of a pointer on all supported plaftorms is at least 4 bytes. * ofs is positive and less than the list size at the beginning of each iteration. https://bugs.python.org/issue35091

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+4-8Lines changed: 4 additions & 8 deletions

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‎Objects/listobject.c‎

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+4-8Lines changed: 4 additions & 8 deletions

Original file line number	Diff line number	Diff line change
@@ -1380,9 +1380,8 @@ gallop_left(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_
1380	1380	while (ofs < maxofs) {
1381	1381	IFLT(a[ofs], key) {
1382	1382	lastofs = ofs;
	1383	+ assert(ofs <= (PY_SSIZE_T_MAX - 1) / 2);
1383	1384	ofs = (ofs << 1) + 1;
1384		- if (ofs <= 0) /* int overflow */
1385		- ofs = maxofs;
1386	1385	}
1387	1386	else /* key <= a[hint + ofs] */
1388	1387	break;
@@ -1403,9 +1402,8 @@ gallop_left(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize_
1403	1402	break;
1404	1403	/* key <= a[hint - ofs] */
1405	1404	lastofs = ofs;
	1405	+ assert(ofs <= (PY_SSIZE_T_MAX - 1) / 2);
1406	1406	ofs = (ofs << 1) + 1;
1407		- if (ofs <= 0) /* int overflow */
1408		- ofs = maxofs;
1409	1407	}
1410	1408	if (ofs > maxofs)
1411	1409	ofs = maxofs;
@@ -1471,9 +1469,8 @@ gallop_right(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize
1471	1469	while (ofs < maxofs) {
1472	1470	IFLT(key, *(a-ofs)) {
1473	1471	lastofs = ofs;
	1472	+ assert(ofs <= (PY_SSIZE_T_MAX - 1) / 2);
1474	1473	ofs = (ofs << 1) + 1;
1475		- if (ofs <= 0) /* int overflow */
1476		- ofs = maxofs;
1477	1474	}
1478	1475	else /* a[hint - ofs] <= key */
1479	1476	break;
@@ -1495,9 +1492,8 @@ gallop_right(MergeState *ms, PyObject *key, PyObject **a, Py_ssize_t n, Py_ssize
1495	1492	break;
1496	1493	/* a[hint + ofs] <= key */
1497	1494	lastofs = ofs;
	1495	+ assert(ofs <= (PY_SSIZE_T_MAX - 1) / 2);
1498	1496	ofs = (ofs << 1) + 1;
1499		- if (ofs <= 0) /* int overflow */
1500		- ofs = maxofs;
1501	1497	}
1502	1498	if (ofs > maxofs)
1503	1499	ofs = maxofs;

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