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Assert AR table entry stability on replace #13705

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Merged
merged 1 commit into from
Jul 16, 2025

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sferik
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@sferik sferik commented Jun 25, 2025

Improve hash internal iteration by verifying that AR table entries remain stable after st_update_callback_func replaces a key-value pair. Fixes a TODO by @ko1 from 2019.

hash.c Outdated
Comment on lines 883 to 887
ar_table_pair *orig_pair = pair;
(*replace)(&key, &val, arg, TRUE);

// TODO: pair should be same as pair before.
pair = RHASH_AR_TABLE_REF(hash, i);
HASH_ASSERT(orig_pair == pair);
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Reading this, I think what the original TODO may have intended is that in non-debug builds, maybe we don't need to do the RHASH_AR_TABLE_REF lookup a second time? What do you think?

Suggested change
ar_table_pair *orig_pair = pair;
(*replace)(&key, &val, arg, TRUE);
// TODO: pair should be same as pair before.
pair = RHASH_AR_TABLE_REF(hash, i);
HASH_ASSERT(orig_pair == pair);
(*replace)(&key, &val, arg, TRUE);
// Pair should not have moved
HASH_ASSERT(pair == RHASH_AR_TABLE_REF(hash, i));

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This makes sense to me. I tried committing your patch but got the error:

Applying suggestions on deleted lines is currently not supported.

I'm going to manually apply your patch and push it for review.

I'd love for @ko1 to comment on his original intent for this TODO.a

@sferik sferik force-pushed the ar-table-replace branch from 5b1aff3 to 78771c7 Compare July 4, 2025 01:24
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sferik commented Jul 16, 2025

@jhawthorn Anything else you need me to change before this is merged?

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Nope! I meant to merge this last week.

@jhawthorn jhawthorn merged commit abc8745 into ruby:master Jul 16, 2025
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It's nice to see you opening PRs to Ruby Erik ❤️

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sferik commented Jul 16, 2025

Thanks! Now that they're being merged, I'm encouraged to make some more!

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2 participants