Sam Price added the comment:
Does not happen on windows.
Error is in cfield.c
```
#ifndef MS_WIN32
} else if (bitsize /* this is a bitfield request */
&& *pfield_size /* we have a bitfield open */
&& dict->size * 8 >= *pfield_size
&& (*pbitofs + bitsize) <=
New submission from Sam Price :
if 8 1 byte fields are included in a ctype field, it allows an extra byte to be
included in the packing when there is no room left for the next field.
If I put the bitfields in a child structure then I get expected results.
In [35]: run ctypeSizeTest.py
Size
