Description
Bug report
Bug description:
Python 3.14 implements a special field _layout_ in ctypes.Structure that allows the programmer to explicitly choose the layout rules for bitfields used by either GCC/Clang or MSVC. The default layout is appropiate for the OS platform (MSVC on Windows, GCC otherwise) which is expected behaviour. It is also possible to use field _pack_ to change the layout to match the compiler. This is currently only implemented for the MSVC layout, not for GCC.
The problem is that using _pack_ on non-Windows systems silently switches the layout rules from GCC to MSVC, which is an unexpected layout by default on non-Windows systems. I propose that this case be handled as an error (NotImplementedError) rather than the silent layout switch. The error message may contain a hint that if the MSVC layout is indeed what is intended, one need to select it explicitly by setting field _layout_.
From the Zen of Python:
Explicit is better than implicit.
Readability counts.
Special cases aren't special enough to break the rules.
Errors should never pass silently.
Tested on 3.14a6
CPython versions tested on:
3.14
Operating systems tested on:
macOS