It's not clear to me that this is the right fix. With this change, it's now impossible to get the bit offset of a struct field.

It's not clear to me that this is the right fix. With this change, it's now impossible to get the bit offset of a struct field.

Getting offset should be use https://github.com/python/cpython/blob/master/Modules/_ctypes/cfield.c#L254

Getting offset should be use https://github.com/python/cpython/blob/master/Modules/_ctypes/cfield.c#L254

What if I want the bit offset and not the byte offset? Consider:

class S(ctypes.Structure):
    _fields_ = [
        ('a', ctypes.c_uint8),
        ('b', ctypes.c_uint8, 6),
        ('c', ctypes.c_uint8, 2),
    ]

Previously, I could do:

>>> S.c.size >> 16  # number of bits
2
>>> S.c.size & 0xFFFF  # bit offset
6
>>> S.c.offset  # byte offset
1

Obviously this API didn't make much sense from the current documentation, but it was at least possible to extract this information. How would I calculate those three values with your patch?

Getting offset should be use https://github.com/python/cpython/blob/master/Modules/_ctypes/cfield.c#L254

What if I want the bit offset and not the byte offset? Consider:

class S(ctypes.Structure):
    _fields_ = [
        ('a', ctypes.c_uint8),
        ('b', ctypes.c_uint8, 6),
        ('c', ctypes.c_uint8, 2),
    ]

Previously, I could do:

>>> S.c.size >> 16  # number of bits
2
>>> S.c.size & 0xFFFF  # bit offset
6
>>> S.c.offset  # byte offset
1

Obviously this API didn't make much sense from the current documentation, but it was at least possible to extract this information. How would I calculate those three values with your patch?

en, I think it should be a inner behavior. Why the user should know this detail?