gh-134889: Fix handling of a few opcodes when optimizing LOAD_FAST

[mpage]

We were incorrectly handling a few opcodes that leave their operands on the stack. Treat all of these conservatively; assume that they always leave operands on the stack.

• FORMAT_SIMPLE leaves its operand on the stack if its a unicode object.
• GET_YIELD_FROM_ITER leaves its operand on the stack if its a coroutine or generator object.
• END_SEND leaves the TOS in place.
• SET_FUNCTION_ATTRIBUTE leaves the TOS in place.
• PUSH_EXC_INFO leaves the TOS in place.
• LOAD_SPECIAL may leave the TOS (self) in place.

• Issue: Python 3.14+: python: Objects/unicodeobject.c:10387: _PyUnicode_JoinArray: Assertion res_data == PyUnicode_1BYTE_DATA(res) + kind * PyUnicode_GET_LENGTH(res)' failed.` in sqlglot #134889

[mgorny]

I suppose this means Python 3.14 is going to see an ABI breakage too, is that correct?

[mpage]

I suppose this means Python 3.14 is going to see an ABI breakage too, is that correct?

I don’t think so. This doesn’t change the binary layout of anything. What about this would cause an ABI breakage?

[thesamesam]

It changed PYC_MAGIC_NUMBER (which is fine if it can't be avoided, it's just a pain if it can be).

[mpage]

It changed PYC_MAGIC_NUMBER (which is fine if it can't be avoided, it's just a pain if it can be).

I think I’m missing something. The magic number changes with every minor release. Since we haven’t released 3.14 yet, bumping the magic number shouldn’t cause any additional pain beyond what’s felt with a normal release.

[mgorny]

A few Linux distributions have already engaged in a lot of Python 3.14 testing (at least Fedora and Gentoo I'm aware of), and these systems will be affected by the magic number change.

[hroncok]

In Fedora, we can deal with the chnage of the magic number in b3. But the sooner it happens the better.

[miss-islington-app]

Thanks @mpage for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @mpage, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 6b77af257c25d31f1f137e477cb23e63692ddf29 3.14

[bedevere-app]

GH-135187 is a backport of this pull request to the 3.14 branch.