aio-libs / multidict / 37118459982

86%

push

github

Split entry_t into a shared compact layout and an anystr layout (#1656)

<!-- Thank you for your contribution! -->

## What do these changes do?

Split `entry_t` into the key and value layout every table kind shares,
which is exactly what a compact table stores, and `anystr_entry_t`,
which embeds it and adds the identity and its hash. Before, `entry_t`
declared all four fields although a compact table holds only two, so
nothing stopped code from reaching `->identity` or `->hash` on a compact
entry. Code that is the same for every kind keeps using `entry_t*`; the
anystr branches reach the extra fields through `as_anystr()`, and
`load_hash()` now takes an `anystr_entry_t*`.

The emitted code is unchanged apart from the COLD
`_md_clone_after_holes()`, whose target is always anystr and which no
longer checks the kind (157 to 141 instructions on GIL). C extension
only; the pure-Python backend has no such layout.

## Are there changes in behavior for the user?

No.

## Is it a substantial burden for the maintainers to support this?

No. It makes the per-kind layouts explicit types, so a wrong field
access on a compact entry no longer compiles silently.

## Related issue number

N/A

## Checklist

- [x] I think the code is well written
- [x] Unit tests for the changes exist (N/A: no behavior change; the
existing suite covers both table kinds)
- [x] Documentation reflects the changes (N/A: internal only)
- [ ] If you provide code modification, please add yourself to
`CONTRIBUTORS.txt` (N/A: no such file in this repo)
- [x] Add a new news fragment into the `CHANGES/` folder
- [x] `make doc-spelling` passes and any new technical words are added
to `docs/spelling_wordlist.txt`

<details>
<summary>Agent run details (optional, for reviewers)</summary>

Codegen: `tools/codegen_diff.py --ref 104f9848` on 3.14.7 and 3.14.7t;
after normalizing `.text.unlikely` relocation offsets (shifted by the
smaller cold function), only `_md_clone_after_holes` differs on both
build... (continued)

791 of 1582 branches covered (50.0%)

Branch coverage included in aggregate %.

9207 of 10051 relevant lines covered (91.6%)

1.83 hits per line