The signal.signal() function directly compares PyObject *handler with PyObject *modstate->ignore_handler. This works on most platforms because they are both small ints and Python uses singletons for cached small ints.

The assumption breaks when Python is built without small int cache or a platform has SIG_IGN / SIG_DFL that is outside the range of small int cache. The wasm32-emscripten platform uses "((void (*)(int))-2)" (4294967294) for SIG_IGN. The wrong comparison breaks several tests on WASM32. The function should use PyObject_RichCompareBool(handler, modstate->ignore_handler, Py_EQ) instead.

    if (handler == modstate->ignore_handler) {
        func = SIG_IGN;
    }
    else if (handler == modstate->default_handler) {
        func = SIG_DFL;
    }

https://github.com/python/cpython/blob/7f4b69b9076bdbcea31f6ad16eb125ee99cf0175/Modules/signalmodule.c#L530-L534

See msg234768 and issue23325. I propose to close this as a duplicate of issue23325.

Yes, it's a duplicate.