The previous code was perfectly fine with `-fwrapv` since it makes signed overflow behaviour defined. And afaik BDFLs stance is that signed integer overflow should be defined to wrap anyhow.

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In my opinion the `-fwrapv` itself makes one proliferate all these insane wrap-checks; indeed I'd rather have them defined in a macro, something like

    if (PYSSIZE_OVERFLOWS_ON_ADD(va.len, vb.len)) {
        PyErr_NoMemory();
        goto done;
    }

    size = va.len + vb.len;

even though `-fwrapv` is defined; that way it'd be obvious what is supposed to happen there.