Function raise_from

include/pybind11/pytypes.h:812–836

Replaces the current Python error indicator with the chosen error, performing a 'raise from' to indicate that the chosen error was caused by the original error.

/// Replaces the current Python error indicator with the chosen error, performing a
/// 'raise from' to indicate that the chosen error was caused by the original error.
inline void raise_from(PyObject *type, const char *message) {
    // Based on _PyErr_FormatVFromCause:
    // https://github.com/python/cpython/blob/467ab194fc6189d9f7310c89937c51abeac56839/Python/errors.c#L405
    // See https://github.com/pybind/pybind11/pull/2112 for details.
    PyObject *exc = nullptr, *val = nullptr, *val2 = nullptr, *tb = nullptr;

    assert(PyErr_Occurred());
    PyErr_Fetch(&exc, &val, &tb);
    PyErr_NormalizeException(&exc, &val, &tb);
    if (tb != nullptr) {
        PyException_SetTraceback(val, tb);
        Py_DECREF(tb);
    }
    Py_DECREF(exc);
    assert(!PyErr_Occurred());

    PyErr_SetString(type, message);

    PyErr_Fetch(&exc, &val2, &tb);
    PyErr_NormalizeException(&exc, &val2, &tb);
    Py_INCREF(val);
    PyException_SetCause(val2, val);
    PyException_SetContext(val2, val);
    PyErr_Restore(exc, val2, tb);
}

/// Sets the current Python error indicator with the chosen error, performing a 'raise from'
/// from the error contained in error_already_set to indicate that the chosen error was