From ce9bbc0a213bfb21b77ada8de5346be5e350e3c4 Mon Sep 17 00:00:00 2001 From: "Ralf W. Grosse-Kunstleve" Date: Tue, 23 May 2023 10:03:33 -0700 Subject: [PATCH] Python 3.11+: Add `__notes__` to `error_already_set::what()` output. (#4678) * First version adding `__notes__` to `error_already_set::what()` output. * Fix trivial oversight (missing adjustment in existing test). * Minor enhancements of new code. * Re-enable `cmake --target cpptest -j 2` * Revert "Re-enable `cmake --target cpptest -j 2`" This reverts commit 60816285e9e7b95b7d33a60805888b80b2bec641. * Add general comment explaining why the `error_fetch_and_normalize` code is so unusual. --- include/pybind11/pytypes.h | 70 +++++++++++++++++++++++++++++++++----- tests/test_exceptions.py | 36 +++++++++++++++----- 2 files changed, 90 insertions(+), 16 deletions(-) diff --git a/include/pybind11/pytypes.h b/include/pybind11/pytypes.h index f11ed5da78..f5d3f34f38 100644 --- a/include/pybind11/pytypes.h +++ b/include/pybind11/pytypes.h @@ -471,13 +471,24 @@ inline const char *obj_class_name(PyObject *obj) { std::string error_string(); +// The code in this struct is very unusual, to minimize the chances of +// masking bugs (elsewhere) by errors during the error handling (here). +// This is meant to be a lifeline for troubleshooting long-running processes +// that crash under conditions that are virtually impossible to reproduce. +// Low-level implementation alternatives are preferred to higher-level ones +// that might raise cascading exceptions. Last-ditch-kind-of attempts are made +// to report as much of the original error as possible, even if there are +// secondary issues obtaining some of the details. struct error_fetch_and_normalize { - // Immediate normalization is long-established behavior (starting with - // https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011 - // from Sep 2016) and safest. Normalization could be deferred, but this could mask - // errors elsewhere, the performance gain is very minor in typical situations - // (usually the dominant bottleneck is EH unwinding), and the implementation here - // would be more complex. + // This comment only applies to Python <= 3.11: + // Immediate normalization is long-established behavior (starting with + // https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011 + // from Sep 2016) and safest. Normalization could be deferred, but this could mask + // errors elsewhere, the performance gain is very minor in typical situations + // (usually the dominant bottleneck is EH unwinding), and the implementation here + // would be more complex. + // Starting with Python 3.12, PyErr_Fetch() normalizes exceptions immediately. + // Any errors during normalization are tracked under __notes__. explicit error_fetch_and_normalize(const char *called) { PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr()); if (!m_type) { @@ -492,6 +503,14 @@ struct error_fetch_and_normalize { "of the original active exception type."); } m_lazy_error_string = exc_type_name_orig; +#if PY_VERSION_HEX >= 0x030C0000 + // The presence of __notes__ is likely due to exception normalization + // errors, although that is not necessarily true, therefore insert a + // hint only: + if (PyObject_HasAttrString(m_value.ptr(), "__notes__")) { + m_lazy_error_string += "[WITH __notes__]"; + } +#else // PyErr_NormalizeException() may change the exception type if there are cascading // failures. This can potentially be extremely confusing. PyErr_NormalizeException(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr()); @@ -506,12 +525,12 @@ struct error_fetch_and_normalize { + " failed to obtain the name " "of the normalized active exception type."); } -#if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00 +# if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00 // This behavior runs the risk of masking errors in the error handling, but avoids a // conflict with PyPy, which relies on the normalization here to change OSError to // FileNotFoundError (https://github.com/pybind/pybind11/issues/4075). m_lazy_error_string = exc_type_name_norm; -#else +# else if (exc_type_name_norm != m_lazy_error_string) { std::string msg = std::string(called) + ": MISMATCH of original and normalized " @@ -523,6 +542,7 @@ struct error_fetch_and_normalize { msg += ": " + format_value_and_trace(); pybind11_fail(msg); } +# endif #endif } @@ -558,6 +578,40 @@ struct error_fetch_and_normalize { } } } +#if PY_VERSION_HEX >= 0x030B0000 + auto notes + = reinterpret_steal(PyObject_GetAttrString(m_value.ptr(), "__notes__")); + if (!notes) { + PyErr_Clear(); // No notes is good news. + } else { + auto len_notes = PyList_Size(notes.ptr()); + if (len_notes < 0) { + result += "\nFAILURE obtaining len(__notes__): " + detail::error_string(); + } else { + result += "\n__notes__ (len=" + std::to_string(len_notes) + "):"; + for (ssize_t i = 0; i < len_notes; i++) { + PyObject *note = PyList_GET_ITEM(notes.ptr(), i); + auto note_bytes = reinterpret_steal( + PyUnicode_AsEncodedString(note, "utf-8", "backslashreplace")); + if (!note_bytes) { + result += "\nFAILURE obtaining __notes__[" + std::to_string(i) + + "]: " + detail::error_string(); + } else { + char *buffer = nullptr; + Py_ssize_t length = 0; + if (PyBytes_AsStringAndSize(note_bytes.ptr(), &buffer, &length) + == -1) { + result += "\nFAILURE formatting __notes__[" + std::to_string(i) + + "]: " + detail::error_string(); + } else { + result += '\n'; + result += std::string(buffer, static_cast(length)); + } + } + } + } + } +#endif } else { result = ""; } diff --git a/tests/test_exceptions.py b/tests/test_exceptions.py index a92ab59a34..ccac4536d6 100644 --- a/tests/test_exceptions.py +++ b/tests/test_exceptions.py @@ -317,13 +317,7 @@ def test_error_already_set_what_with_happy_exceptions( assert what == expected_what -@pytest.mark.skipif( - # Intentionally very specific: - "sys.version_info == (3, 12, 0, 'alpha', 7)", - reason="WIP: https://github.com/python/cpython/issues/102594", -) -@pytest.mark.skipif("env.PYPY", reason="PyErr_NormalizeException Segmentation fault") -def test_flaky_exception_failure_point_init(): +def _test_flaky_exception_failure_point_init_before_py_3_12(): with pytest.raises(RuntimeError) as excinfo: m.error_already_set_what(FlakyException, ("failure_point_init",)) lines = str(excinfo.value).splitlines() @@ -337,7 +331,33 @@ def test_flaky_exception_failure_point_init(): # Checking the first two lines of the traceback as formatted in error_string(): assert "test_exceptions.py(" in lines[3] assert lines[3].endswith("): __init__") - assert lines[4].endswith("): test_flaky_exception_failure_point_init") + assert lines[4].endswith( + "): _test_flaky_exception_failure_point_init_before_py_3_12" + ) + + +def _test_flaky_exception_failure_point_init_py_3_12(): + # Behavior change in Python 3.12: https://github.com/python/cpython/issues/102594 + what, py_err_set_after_what = m.error_already_set_what( + FlakyException, ("failure_point_init",) + ) + assert not py_err_set_after_what + lines = what.splitlines() + assert lines[0].endswith("ValueError[WITH __notes__]: triggered_failure_point_init") + assert lines[1] == "__notes__ (len=1):" + assert "Normalization failed:" in lines[2] + assert "FlakyException" in lines[2] + + +@pytest.mark.skipif( + "env.PYPY and sys.version_info[:2] < (3, 12)", + reason="PyErr_NormalizeException Segmentation fault", +) +def test_flaky_exception_failure_point_init(): + if sys.version_info[:2] < (3, 12): + _test_flaky_exception_failure_point_init_before_py_3_12() + else: + _test_flaky_exception_failure_point_init_py_3_12() def test_flaky_exception_failure_point_str():