gh-131093: Enforce -std=c11 for gcc at configure time rather than make time

[CS-cwhite]

When compiling under gcc, configure.ac currently assumes -std=c11 rather than checking it. This causes configure to succeed but make to fail on old compilers. Fix this by adding a check for -std=c11 in configure.ac.

The changes to configure are the result of running Tools/build/regen-configure.sh.

Manual test on gcc 4.4.7:

Before:

$ ./configure
... (after it builds for a while)
gcc -std=gnu99 -pthread -c -fno-strict-overflow -Wsign-compare ...  -DPy_BUILD_CORE -o Parser/lexer/buffer.o Parser/lexer/buffer.c
cc1: error: unrecognized command line option "-std=c11"cc1: error: unrecognized command line option "-std=c11"

After:

$ ./configure
...
checking whether C compiler accepts -std=c11... no
configure: error: Python requires -std=c11 on gcc

Fixes #131093.

• Issue: configure.ac assumes -std=c11 rather than checking it, which causes make failures on old compilers #131093

[python-cla-bot]

The following commit authors need to sign the Contributor License Agreement:

• [email protected]

[CS-cwhite]

I previously signed the CLA on behalf of my organization, at the direction of the organization's legal department. Is there a way to tell CLA-bot to recognize that?

[AA-Turner]

cc @ambv re CLA

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @AA-Turner for commit b4fbd36 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F133608%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[CS-cwhite]

This is my first cpython PR, so I don't know --- do I have any action items from the build failures? E.g., Check if generated files are up to date appears to be checking C code, and this PR doesn't touch any C code. The failures don't appear to be related to this PR's changes, but I'm happy to work on fixes if they are!

[AA-Turner]

We had some teething issues with the bump to 3.15, so I've updated the branch to check the failures aren't related. In general, you may find the Python Developer's Guide useful.

A

[ZeroIntensity]

I previously signed the CLA on behalf of my organization, at the direction of the organization's legal department.

I think redoing the commits with whatever email you signed with and then force-pushing should work.

[CS-cwhite]

@ZeroIntensity Thanks! I checked, and the email is the same. However, the author name was different (it was "Chris White" in the commit but "Christopher White" on the CLA). I amended the commit to show the same name as the CLA in case that made a difference.

[AA-Turner]

I've asked internally for advice.

A

[AA-Turner]

@CS-cwhite, the advice I've had is that you should click the button to sign the CLA again. Sorry for the delay and the trouble this has caused. There's some more background/colour in #120171 (comment)

A

[erlend-aasland]

Suggested change

	works. This way you don't hit an "invalid option" error at make time on old
	works. This way you don't hit an "invalid option" error at build time on old