Actually, you're right. For now, PyErr_Occurred is a GIL lock plus a memory access. While the access is cheap because of a L1 cache hit, the GIL takes its toll in a hot path.

So I'm closing the PR until GIL removal is done so no performance penalty will be imposed.

I could use _PyErr_Occurred because "Currently Argument Clinic is considered internal-only for CPython", but it requires extra modifications of the clinic that is undesirable.