Patch - updates maybe_indices_to_slice to use intp_t
- [ ] closes ##59531 (https://github.com/pandas-dev/pandas/issues/59531)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Happy to give it a try.  I'll let you know. Do you mean intp_t ?  If so, changing max_len to intp_t and np.intp respectively in lib.pyx and lib.pyi (to match the array definitions) also produces expected results:

```
>>> import pandas as pd
>>> print (pd.__version__)
3.0.0.dev0+1351.g523afa840a.dirty
>>> test = pd.read_pickle("summary.pkl")
>>> summary = test[test['count'] > 0]
>>> print (len(test))
4261028590
>>> print (len(summary))
1621743
```

Very minor changes but happy to submit another PR if that works for you. Yes that's correct. You can just update this PR - no need to create another Got there.... Many thanks for your help! :) @benjamindonnachie great I think this change looks pretty good! Let's see if CI is green.

You will also want to add a whatsnew entry, which can be added to pandas/doc/source/whatsnew/v3.0.0.rst`  You can add it to the section on Bug Fixes > Indexing (just follow the same pattern you see for other notes already there) Whatsnew/v3.0.0.rst updated.  Fingers crossed! :) This pull request is stale because it has been open for thirty days with no activity. Please [update](https://pandas.pydata.org/pandas-docs/stable/development/contributing.html#updating-your-pull-request) and respond to this comment if you're still interested in working on this. Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen. @mroeschke  I'm not sure what else you need given the minor nature of this patch. It appeared the code checks were not all passing https://github.com/pandas-dev/pandas/actions/runs/10938423968/job/30366432851 @benjamindonnachie any plans to revive this PR?  Otherwise, I will - I'm affected by this bug as well. Opened #61080 as a replacement, but left @benjamindonnachie as the original author.