Importing ctypes results in extra open libffi file descriptor since 3.14

Bug report

Bug description:

On python 3.13 (Fedora), importing ctypes results in the following output from lsfd:

python3 893377 daandemeyer    mem r-x---  REG   0:37     0  304862113 /usr/lib64/libffi.so.8.1.4
python3 893377 daandemeyer    mem r-----  REG   0:37     0  304862113 /usr/lib64/libffi.so.8.1.4
python3 893377 daandemeyer    mem r-----  REG   0:37     0  304862113 /usr/lib64/libffi.so.8.1.4
python3 893377 daandemeyer    mem rw----  REG   0:37     0  304862113 /usr/lib64/libffi.so.8.1.4

On python 3.14 (Fedora), importing ctypes results in the following output from lsfd:

python3 892407 daandemeyer      5 r-----  REG  0:238  1342       7553 /usr/lib64/libffi.so.8.2.0

This ended up breaking https://github.com/systemd/mkosi because it relied on the fact that no new regular file descriptors were opened by importing ctypes (on python 3.14 the file descriptor shows up in /proc/self/fd whereas on python 3.13 the file descriptors are memory maps which don't show up in /proc/self/fd). I searched through the commit list and couldn't find the commit that introduced this change. It also didn't seem to be documented in the release notes. Can anyone point me to the commit introducing this change and the reasoning behind it?

CPython versions tested on:

3.14

Operating systems tested on:

Linux

首先，按照报告中的方法，使用 lsfd 和 /proc/self/fd 比较 Linux 上 Python 3.13 和 3.14 中的 ctypes 导入情况。追踪 CPython 的提交历史，找出使 libffi 显示为普通文件描述符的更改，然后确定其原因，以及这种行为是否需要回归修复或发布说明文档。完成的标准是明确识别并验证该更改及其原因。