python
static_assert undefined (with C11 compiler) on macOS <= 10.10
Bug report
Python 3.11 fails to build on macOS 10.10 because static_assert is not defined by the libc headers, even when using a C11 compiler. A workaround like the one in place for FreeBSD is needed.
Your environment
- CPython versions tested on: 3.11.0
- Operating system and architecture: macOS 10.10 x86_64
- PR: gh-94766
Isn't MacOS 10.10 unsupported since 2017?
By Apple, but there are still many users of older versions of macOS. The python.org macOS installers currently support running on systems back through macOS 10.9 (but the binaries are built on newer versions on macOS so would not see this build error) and the MacPorts project (where this issue originated) supports back to macOS 10.6 and earlier.
I have no issue on principle with supporting builds on Mac OS X 10.9 even if that's no longer supported by Apple. That being said, it's a question worth asking: how long will we commit to supporting ancient macOS versions with the latest Python? I mean, GH-94766 isn't particularly bad but it's one example of additional maintenance required.
For Windows we dropped Windows 7 support not long after it was dropped by Microsoft and the first Windows 7-specific issue arose. There are some complaints about that but it's a somewhat strange requirement: the latest Python version on a very old operating system. For Windows users, we said: hey, Python 3.7 and 3.8 are still supported, use those instead on Windows 7.
Maybe at some point we should say the same about 10.9 Mavericks, unsupported since September 2016? Again, there are still-supported versions of Python that you can install on those old operating systems. The question is: should 3.12 keep piling workarounds for it?
From our (MacPorts) point of view, we're going to be adding these workarounds downstream anyway for a long time to come, so we might as well send them upstream.
Isn't MacOS 10.10 unsupported since 2017?
By Apple, but there are still many users of older versions of macOS. The python.org macOS installers currently support running on systems back through macOS 10.9 (but the binaries are built on newer versions on macOS so would not see this build error) and the MacPorts project (where this issue originated) supports back to macOS 10.6 and earlier.
Off-topic for this issue, but we need to start thinking about which OS releases we want to support in the installer. The Xcode 14 release notes mention:
Building for deployment to OS releases older than macOS 10.13, iOS 11, tvOS 11, and watchOS 4 is no longer supported. (92834476)
Apple no longer supports deploying to older macOS versions than 10.13 with the latest version of Xcode, while we should use the latest compiler and SDK to get best performance and access to new APIs.
W.r.t. this particular issue I don't mind adding a workaround for this given that a similar workaround is present for FreeBSD.
WRT the dropping of support for older macOS releases in the latest Xcode/CLT, I plan to provide a new installer variant for 3.12 pre-releases that will use the latest tools. More to follow after alpha 2.
Pinging as per the dev guide since the PR has been awaiting review for over a month.
@jmroot's fix for the immediate problem was merged by @vstinner to main in #94766 and in 3.11 (for 3.11.4) in #103282.
I believe this last patch https://github.com/python/cpython/pull/103282 is what makes build to fail on ARMv5 using gcc 4.6.4. This was working previously with Python 3.11.3 and fails since 3.11.4.
Here's my related PR to build Python 3.10 and 3.11 pacakges for Synology linux NAS https://github.com/SynoCommunity/spksrc/pull/5800
EDIT: Confirmed, now having a revert patch for that specific arch armv5. https://github.com/SynoCommunity/spksrc/pull/5800/commits/8ca07f5b74ebba8789a40352781ea082e6387ed6 Note for others who may be in the same boat, in order to succesfully build Python 3.x using gcc 4.64 on armv5 where also enforcing C99 thus extending our luck a little longer https://github.com/SynoCommunity/spksrc/blob/master/cross/python311/patches/88f6281/005-configure.ac-remove-unknown-flags.patch
Relying on _Static_assert being accepted in C99 mode is certainly a hack, but if that's your goal you can probably get away with just removing or modifying the __STDC_VERSION__ >= 201112L part of the check.