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gh-111140: Fix edge case in PyLong_AsNativeBytes where large negative longs may require an extra byte #116053

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Merged
encukou merged 19 commits into from
Apr 5, 2024
Merged

gh-111140: Fix edge case in PyLong_AsNativeBytes where large negative longs may require an extra byte #116053

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d5b0e98
gh-111140: Fix edge case in PyLong_AsNativeBytes where large negative…
zooba Feb 28, 2024
f162348
Improved edge case testing and fuzz tests
zooba Mar 1, 2024
0efa143
Test comments
zooba Mar 1, 2024
15b3752
Fix for x86
zooba Mar 4, 2024
fbe42e7
Merge remote-tracking branch 'upstream/main' into gh-111140
zooba Mar 19, 2024
8dedad7
More precise check for unsigned non-overflow
zooba Mar 19, 2024
d3deebf
Merge branch 'main' into gh-111140
zooba Mar 28, 2024
621708c
Change endianness arguments to flags to allow additional arguments
zooba Mar 28, 2024
c607f04
Space
zooba Mar 28, 2024
140c011
Fix tests, one result, and docs
zooba Mar 28, 2024
77097bf
Fix test
zooba Mar 28, 2024
a8e2540
Update NEWS
zooba Mar 28, 2024
5ba6451
Missed colon
zooba Mar 28, 2024
68b9d8e
Doc fixes and improved test failure output
zooba Apr 2, 2024
37ad671
Remove my deliberate failure
zooba Apr 2, 2024
1e615cf
Reword PyLong_AsNativeBytes docs (#33)
encukou Apr 4, 2024
d1b886c
Apply PR feedback
zooba Apr 4, 2024
38ecfe2
Merge branch 'gh-111140' of https://github.com/zooba/cpython into gh-…
zooba Apr 4, 2024
614a6ae
Check for new error
zooba Apr 4, 2024
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@zooba
zooba committed Apr 4, 2024
commit d1b886c549ffb66b70a739e3c94338baba2a5e35
21 changes: 11 additions & 10 deletions Objects/longobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1088,10 +1088,7 @@ _resolve_endianness(int *endianness)
} else {
*endianness &= 1;
}
if (*endianness != 0 && *endianness != 1) {
PyErr_SetString(PyExc_SystemError, "invalid 'endianness' value");
return -1;
}
assert(*endianness == 0 || *endianness == 1);
return 0;
}

Expand Down Expand Up @@ -1129,7 +1126,7 @@ PyLong_AsNativeBytes(PyObject* vv, void* buffer, Py_ssize_t n, int flags)

if ((flags != -1 && (flags & Py_ASNATIVEBYTES_REJECT_NEGATIVE))
&& _PyLong_IsNegative(v)) {
PyErr_SetString(PyExc_OverflowError, "Cannot convert negative int");
PyErr_SetString(PyExc_ValueError, "Cannot convert negative int");
if (do_decref) {
Py_DECREF(v);
}
Expand Down Expand Up @@ -1222,16 +1219,20 @@ PyLong_AsNativeBytes(PyObject* vv, void* buffer, Py_ssize_t n, int flags)
/* Calculates the number of bits required for the *absolute* value
* of v. This does not take sign into account, only magnitude. */
size_t nb = _PyLong_NumBits((PyObject *)v);
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/* Normally this would be((nb - 1) / 8) + 1 to avoid rounding up
* multiples of 8 to the next byte, but we add an implied bit for
* the sign and it cancels out. */
res = (Py_ssize_t)(nb / 8) + 1;
if (nb == (size_t)-1) {
res = -1;
} else {
/* Normally this would be((nb - 1) / 8) + 1 to avoid rounding up
* multiples of 8 to the next byte, but we add an implied bit for
* the sign and it cancels out. */
res = (Py_ssize_t)(nb / 8) + 1;
}

/* Two edge cases exist that are best handled after extracting the
* bits. These may result in us reporting overflow when the value
* actually fits.
*/
if (n > 0 && res == n + 1 && nb == n * 8) {
if (n > 0 && res == n + 1 && nb % 8 == 0) {
if (_PyLong_IsNegative(v)) {
/* Values of 0x80...00 from negative values that use every
* available bit in the buffer do not require an additional
Expand Down