Can a real function implementation be used as a default handler for a unit test stub?

[LucienMorey]

I have functions that read data buffers directly from a wire and handle endianness transforms to return a proper data type in a common utility library like the one shown below. I can unit-test this function and confirm it works exactly as expected, which is great.

float EndianUtils_float32_from_big_endian(const void *data)
{
    assert(sizeof(float) == sizeof(int32_t));
    float return_value = NAN;
    if (data != NULL)
    {
        uint32_t value = be32toh(*(uint32_t *)data);
        memcpy(&return_value, &value, sizeof(float));
    }
    return return_value;
}

Suppose I use this function in another library's function, like one that implements a decode for a HAL. The function is automatically stubbed out, and the real implementation is ignored in this situation. This is not ideal behaviour because even though the function itself is not subject to testing, its real implementation is required to validate the decode of a byte stream containing multiple sequential fields against data with a known value. Can a real function implementation be used as the default handler for a unit test stub in this situation?

Regards,
Lucien