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gh-64490: Fix bugs in argument clinic varargs processing #32092

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merged 28 commits into from
Nov 24, 2022

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colorfulappl
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@colorfulappl colorfulappl commented Mar 24, 2022

Fix 3 bugs introduced in #18609.

Bug reason lists in each commit's commit message.

https://bugs.python.org/issue20291

Python allows at most *one* vararg in one function.
Remove the improper varargs check which allows function definition like
```
    *vararg1: object
    *vararg2: object
```
in argument clinic.
Variable `vararg` indicates the index of vararg in parameter list.
While copying kwargs to `buf`, the index `i` should not add `vararg`, which leads to an out-of-bound bug.

When there are positional args, vararg and keyword args in a function definition, in which case `vararg` > 1, this bug can be triggered.

e.g.
```
    pos: object
    *args: object
    kw: object
```
The calculation of noptargs is incorrect when there is a vararg.
This bug prevents parsed arguments passing to XXXX_impl function.

e.g.
Define function
```
    *args: object
    kw: object
```
and pass kw=1 to the function, the `kw` parameter won't receive the pass in value.
@erlend-aasland
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Could you also add a NEWS entry?

@bedevere-bot
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Most changes to Python require a NEWS entry.

Please add it using the blurb_it web app or the blurb command-line tool.

@erlend-aasland
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Thanks; still missing the NEWS entry, though.

@colorfulappl
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NEWS added :)

@erlend-aasland erlend-aasland changed the title bpo-20291: Fix bugs in argument clinic varargs processing gh-64490: Fix bugs in argument clinic varargs processing Aug 11, 2022
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NEWS added :)

Thanks; that's some entry! :) Could you narrow it down to a couple of concise sentences that describe the actual changes only?

@erlend-aasland
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Also, could you please add tests for each case?

@colorfulappl
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Also, could you please add tests for each case?

Do you mean put the test cases into test_linic.py?

To see if the OOB bug is fixed in commit 6203962 , I should write some code snippet calling function _PyArg_UnpackKeywordsWithVararg, compile it and ensure that it does not crash.

I'm not sure how can I do this without touching the Python vm or library,
though I have wrote a proof-of-concept by adding a built-in function and test it manually:
https://github.com/colorfulappl/cpython/tree/unpack_keywords_oob_bug_poc .

As for commit 6793f38, I'm looking at test_linic.py and will have a try later.

@erlend-aasland
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Is it still waiting for further changes?

Since gh-96178 has recently been merged, we finally have a test framework for functional clinic tests, so I'd say this PR should add some tests before we are ready to land.

@colorfulappl
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I added some test cases and did another change in a48971d, so this PR may be necessary to be reviewed again. @erlend-aasland @isidentical @kumaraditya303

@kumaraditya303 kumaraditya303 self-requested a review November 24, 2022 06:43
@colorfulappl
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Another change in e6a4e13:
Argument Clinic does not generate noptargs when there is a vararg and no optional argument.

@colorfulappl colorfulappl force-pushed the unpack_keywords_bugfix branch from 6087c2e to c3d6b73 Compare November 24, 2022 11:29
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LGTM, thanks! Kumar, Batuhan, do you have further remarks?

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LGTM

@erlend-aasland
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@colorfulappl, please fix the merge conflicts

# Conflicts:
#	Lib/test/test_clinic.py
#	Modules/_testclinic.c
#	Modules/clinic/_testclinic.c.h
@erlend-aasland erlend-aasland merged commit 0da7283 into python:main Nov 24, 2022
@miss-islington
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Thanks @colorfulappl for the PR, and @erlend-aasland for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.11.
🐍🍒⛏🤖

@miss-islington
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Sorry, @colorfulappl and @erlend-aasland, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 0da728387c99fe6c127b070f2d250dc5bdd62ee5 3.11

@miss-islington
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Sorry @colorfulappl and @erlend-aasland, I had trouble checking out the 3.10 backport branch.
Please retry by removing and re-adding the "needs backport to 3.10" label.
Alternatively, you can backport using cherry_picker on the command line.
cherry_picker 0da728387c99fe6c127b070f2d250dc5bdd62ee5 3.10

@erlend-aasland
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@kumaraditya303 I'm inclined to backport the functional tests for AC to 3.11 and 3.10. What do you think? We've backported tests to increase coverage in the maintained branches before; it would help backporting the AC fixes (and by the way, we should backport the AC bug fixes that we landed earlier today)

colorfulappl added a commit to colorfulappl/cpython that referenced this pull request Dec 20, 2022
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GH-100368 is a backport of this pull request to the 3.11 branch.

@bedevere-bot bedevere-bot removed the needs backport to 3.11 only security fixes label Dec 20, 2022
@colorfulappl
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I have backported this to 3.11 (#100368).
And since 3.10 Argument Clinic does not support varargs parsing, there is no need to backport this to 3.10, IMHO.

erlend-aasland pushed a commit that referenced this pull request Dec 28, 2022
@serhiy-storchaka serhiy-storchaka removed the needs backport to 3.10 only security fixes label Aug 11, 2024
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It is too later for 3.10.

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10 participants