Free arena on _PyCompile_AstOptimize failure in Py_CompileStringObject

[berkerpeksag]

After commit 10a91d7 introduced arena cleanup, commit 2dfbd4f removed the free call when _PyCompile_AstOptimize fails.

[iritkatriel]

How did you find this? Are you able to write a test?

[berkerpeksag]

I saw the snippet of Py_CompileStringObject in a blog post. I'll see what can I do about writing a minimal test case.

[berkerpeksag]

I took some time to think about how to write a test. If this were a refleak, I would probably launch a Python process with -X showrefcount and make sure that the leak is no longer present. Since this case involves forgetting to free the arena, I can't think of a reliable way to confirm that the leak is fixed in the test case.

Also, it seems that the only way to trigger this issue is by testing Py_CompileStringObject directly in test_capi, which feels a bit excessive.

[miss-islington-app]

Thanks @berkerpeksag for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-128006 is a backport of this pull request to the 3.13 branch.