PEP 7: Python 3.11 uses C99 and C11 #2309

vstinner · 2022-02-07T14:18:09Z

No description provided.

vstinner · 2022-02-07T14:22:24Z

Update PEP 7 to reflect what's being used in practice: https://docs.python.org/dev/whatsnew/3.11.html#build-changes

Building Python now requires a C99 <math.h> header file providing the following functions: copysign(), hypot(), isfinite(), isinf(), isnan(), round(). (Contributed by Victor Stinner in bpo-45440.)
Building Python now requires a C99 <math.h> header file providing a NAN constant, or the __builtin_nan() built-in function. If a platform does not support Not-a-Number (NaN), the Py_NO_NAN macro can be defined in the pyconfig.h file. (Contributed by Victor Stinner in bpo-46640.)

IMO it's no longer worth it to go into details of which C99 features are used or not.

See https://bugs.python.org/issue46640 for @encukou's request about updating the PEP.

I'm only aware of one C99 feature which is causing troubles: https://bugs.python.org/issue40120 This issue is still being discussed, I prefer to not mention it in the PEP.

AA-Turner

Two on grammar

A

pep-0007.txt

tiran · 2022-02-07T15:35:29Z

We cannot require full C11 compatibility becase we have to special case MSVC. MSVC does not implement C11 features. Instead MSVC provides substitutes for APIs. For example MSVC has interlocked variable access instead of stdatomic.

C11 stdatomic.h https://en.cppreference.com/w/c/atomic
MSVC Interlocked Variable Access https://docs.microsoft.com/de-de/windows/win32/sync/interlocked-variable-access

GCC < 4.8 and AFAIK clang < 4.0 are lacking stdatomic support. I'm unsure about ICC. I found second hand information that ICC < 18 has incomplete stdatomic.h. I asked somebody to look into AIX xlc.

vstinner · 2022-02-07T15:55:41Z

We cannot require full C11 compatibility

My change doesn't require C11, but C99.

vstinner · 2022-02-07T15:57:11Z

Two on grammar

Fixed.

vstinner · 2022-02-07T15:58:15Z

cc @gpshead @encukou @pablogsal: Is it ok to require C99 to build Python 3.11? I don't think that we have to go into the details of which C99 features are used by Python, do you?

gvanrossum · 2022-02-07T16:36:04Z

Where was the discussion leading to this PEP change? It shouldn't be happening on this PR -- the peps repo is not for discussions about contents.

vstinner · 2022-02-07T16:47:15Z

@gvanrossum:

Where was the discussion leading to this PEP change? It shouldn't be happening on this PR -- the peps repo is not for discussions about contents.

https://bugs.python.org/issue46640#msg412728

gvanrossum · 2022-02-07T16:50:08Z

That discussion is far from conclusive. Please escalate to python-dev.

vstinner · 2022-02-07T17:10:47Z

That discussion is far from conclusive. Please escalate to python-dev.

Oh, I didn't expect this change to be controversial. Anyway, I created a thread on python-dev: https://mail.python.org/archives/list/python-dev@python.org/thread/J5FSP6J4EITPY5C2UJI7HSL2GQCTCUWN/

CAM-Gerlach

The current version LGTM from a PEP editor perspective, though you may need to modify it pending the outcome of the Python-Dev discussion (C11? Mention C99 features dropped in C11? Explicitly call out features unsupported in MSVC? Clarify that optional features are not supported? Add optional atomic support? etc)

vstinner · 2022-02-23T19:27:42Z

I created a thread on python-dev: https://mail.python.org/archives/list/python-dev@python.org/thread/J5FSP6J4EITPY5C2UJI7HSL2GQCTCUWN/

There is a consensus on using C99 and a willingness to even use some C11 feature, so I updated my PR for that.

@tiran @mdickinson: Does it look good to you?

encukou · 2022-02-24T10:09:07Z

pep-0007.txt

+* Python 3.11 and newer versions use C99 in the public C API and use a
+  subset of C11 in Python internals. The public C API should be
+  compatible with C++. The C11 subset are features supported by GCC 8.5,
+  clang 8.0, and MSVC of Visual Studio 2017.


The public C API should be compatible with C11 as well.
C11 made several features present in C99 optional (most notably variable-length arrays, MSVC doesn't have). Those shouldn't be used in the API.

Ok, let me try something simpler: "Python 3.11 and newer versions use C11 without optional features". Is it better? (see the updated PR)

Not sure if you want to add a reference for that, but a simple overview is:
https://en.wikipedia.org/wiki/C11_%28C_standard_revision%29#Optional_features

That indeed seems helpful

CAM-Gerlach

One grammar correction; otherwise LGTM from a textual perspective. Adding a link to C11 seems to be a good idea, though.

CAM-Gerlach · 2022-02-24T19:21:24Z

pep-0007.txt


-* Python versions greater than or equal to 3.6 use C89 with several
-  select C99 features:
+* Python 3.6 to 3.10 uses C89 with several select C99 features:


Suggested change

* Python 3.6 to 3.10 uses C89 with several select C99 features:

* Python 3.6 to 3.10 use C89 with several select C99 features:

Plural agreement error (grammar)

gvanrossum

Once CAM approves this can go in. Thanks for pushing for this!

pep-0007.txt

AA-Turner · 2022-02-24T20:44:09Z

The latest version of the PR says "C11 without optional features" -- ideally the PR title should be updated before merging too for an accurate commit message.

A

vstinner · 2022-02-24T23:12:47Z

The latest version of the PR says "C11 without optional features" -- ideally the PR title should be updated before merging too for an accurate commit message.

I changed the commit title. GitHub keeps the original commit title. When I click on merge, it uses the commit title, but not the GitHub PR title... I hate that part of GitHub. Gerrit is way better for that, it's possible to review the commit message.

vstinner · 2022-02-24T23:13:16Z

Merged, thanks for the reviews.

gvanrossum · 2022-02-24T23:18:15Z

The latest version of the PR says "C11 without optional features" -- ideally the PR title should be updated before merging too for an accurate commit message.

I changed the commit title. GitHub keeps the original commit title. When I click on merge, it uses the commit title, but not the GitHub PR title... I hate that part of GitHub. Gerrit is way better for that, it's possible to review the commit message.

Must be your git(hub) tooling. When I merge (in the browser) I get to edit the commit title and message.

vstinner · 2022-02-24T23:27:57Z

Must be your git(hub) tooling. When I merge (in the browser) I get to edit the commit title and message.

Yes. I also get a form to edit the PR title. But in my experience, if I modify the commit title in Git and then use git push --force, the GitHub PR title is not updated. And when I merge a PR, the edit form gives me the title from Git as expected.

It's just that I'm too lazy sometimes to update them :-)

Anyway, I modified the merged commit title to omit C99 :-)

CAM-Gerlach · 2022-02-24T23:32:54Z

Yeah, the PR title is auto-filled from the initial commit message if the PR branch only has one commit, but otherwise independent of the commit message, since PRs can have any number of commits and it wouldn't really make sense to arbitrarily lock it to one of them. The PR title can be changed at any time, and the commit message can likewise be modified at will when merging.

Anyway, I modified the merged commit title to omit C99 :-)

On main? 😱

vstinner · 2022-02-24T23:55:12Z

On main? scream

I used the merge form to clean up the commit message. See the final commit: e846b70

CAM-Gerlach · 2022-02-25T00:34:30Z

Understood, thanks. I apologize for the confusion; my fault there.

vstinner requested review from gvanrossum and warsaw as code owners February 7, 2022 14:18

the-knights-who-say-ni added the CLA signed label Feb 7, 2022

AA-Turner reviewed Feb 7, 2022

View reviewed changes

pep-0007.txt Outdated Show resolved Hide resolved

pep-0007.txt Outdated Show resolved Hide resolved

CAM-Gerlach reviewed Feb 15, 2022

View reviewed changes

CAM-Gerlach changed the title ~~Python 3.11 uses C99~~ PEP 7: Require C99 for Python 3.11+ Feb 16, 2022

vstinner changed the title ~~PEP 7: Require C99 for Python 3.11+~~ PEP 7: Python 3.11 uses C99 and C11 Feb 23, 2022

vstinner mentioned this pull request Feb 23, 2022

bpo-46656: Remove Py_NO_NAN macro python/cpython#31160

Merged

encukou reviewed Feb 24, 2022

View reviewed changes

PEP 7: Python 3.11 uses C11

b230af8

CAM-Gerlach reviewed Feb 24, 2022

View reviewed changes

gvanrossum reviewed Feb 24, 2022

View reviewed changes

pep-0007.txt Outdated Show resolved Hide resolved

pep-0007.txt Outdated Show resolved Hide resolved

vstinner added 2 commits February 25, 2022 00:06

Grammar; remove Future C99 features

cd43ebe

Add link

2864440

vstinner merged commit e846b70 into python:main Feb 24, 2022

vstinner deleted the pep7 branch February 24, 2022 23:13

erlend-aasland mentioned this pull request May 13, 2022

pep8/greppable exception messages erlend-aasland/peps#1

Closed

erlend-aasland mentioned this pull request Jun 27, 2022

pep 687/mark as accepted erlend-aasland/peps#2

Closed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

PEP 7: Python 3.11 uses C99 and C11 #2309

PEP 7: Python 3.11 uses C99 and C11 #2309

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

AA-Turner left a comment

tiran commented Feb 7, 2022

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

gvanrossum commented Feb 7, 2022

vstinner commented Feb 7, 2022

gvanrossum commented Feb 7, 2022 via email

vstinner commented Feb 7, 2022

CAM-Gerlach left a comment

vstinner commented Feb 23, 2022

encukou Feb 24, 2022

vstinner Feb 24, 2022

h-vetinari Feb 24, 2022

CAM-Gerlach Feb 24, 2022

CAM-Gerlach left a comment

CAM-Gerlach Feb 24, 2022

gvanrossum left a comment

AA-Turner commented Feb 24, 2022

vstinner commented Feb 24, 2022

vstinner commented Feb 24, 2022

gvanrossum commented Feb 24, 2022

vstinner commented Feb 24, 2022

CAM-Gerlach commented Feb 24, 2022

vstinner commented Feb 24, 2022

CAM-Gerlach commented Feb 25, 2022

	* Python 3.6 to 3.10 uses C89 with several select C99 features:
	* Python 3.6 to 3.10 use C89 with several select C99 features:

PEP 7: Python 3.11 uses C99 and C11 #2309

PEP 7: Python 3.11 uses C99 and C11 #2309

Conversation

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

AA-Turner left a comment

Choose a reason for hiding this comment

tiran commented Feb 7, 2022

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

vstinner commented Feb 7, 2022

gvanrossum commented Feb 7, 2022

vstinner commented Feb 7, 2022

gvanrossum commented Feb 7, 2022 via email

vstinner commented Feb 7, 2022

CAM-Gerlach left a comment

Choose a reason for hiding this comment

vstinner commented Feb 23, 2022

encukou Feb 24, 2022

Choose a reason for hiding this comment

vstinner Feb 24, 2022

Choose a reason for hiding this comment

h-vetinari Feb 24, 2022

Choose a reason for hiding this comment

CAM-Gerlach Feb 24, 2022

Choose a reason for hiding this comment

CAM-Gerlach left a comment

Choose a reason for hiding this comment

CAM-Gerlach Feb 24, 2022

Choose a reason for hiding this comment

gvanrossum left a comment

Choose a reason for hiding this comment

AA-Turner commented Feb 24, 2022

vstinner commented Feb 24, 2022

vstinner commented Feb 24, 2022

gvanrossum commented Feb 24, 2022

vstinner commented Feb 24, 2022

CAM-Gerlach commented Feb 24, 2022

vstinner commented Feb 24, 2022

CAM-Gerlach commented Feb 25, 2022