gh-102192: Replace PyErr_Fetch/Restore etc by more efficient alternatives (in Objects/) by iritkatriel · Pull Request #102218 · python/cpython

iritkatriel

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I don't think this is about PyErr_NormalizeException. This function is called from only one place:

/* Helper that tries to ensure the reported exception chain indicates the
 * codec that was invoked to trigger the failure without changing the type
 * of the exception raised.       
 */
static void
wrap_codec_error(const char *operation,
                 const char *encoding)
{
    /* TrySetFromCause will replace the active exception with a suitably
     * updated clone if it can, otherwise it will leave the original
     * exception alone.
     */
    _PyErr_TrySetFromCause("%s with '%s' codec failed",
                           operation, encoding);
}

This is a classic use case for notes (PEP 678). It is trying to create an exception of the same type with additional info (and does a lot of stuff to check that it can indeed safely create a new exception of the same type).

I would just rewrite this whole thing to attach the additional info as a note (but not in this PR, it's unrelated).