minor ZSET code cleanup: Remove dead guard in deleteRangeCore and enhance buffer contracts

[rainsupreme]

deleteRangeCore handles only ranges whose two boundary leaves differ: fbtreeDeleteRangeByRank descends distinct children (li != ri) before calling it, and the value and score paths route same-leaf ranges to deleteRangeSameLeaf. The guard

if (bp->end_idx < 0 && bp->start_leaf == bp->end_leaf) return 0;

therefore never fires. It also sat directly under a comment explaining that no local empty-range short-circuit belongs at that point, so the code contradicted its own documentation. Replace it with an assert that states the precondition every caller already satisfies, and move the split_depth declaration to the block that uses it.

Every score-prefix parameter in fbtree.c now asserts that it must reference at least SCORE_SIZE readable bytes: read-only prefixes become const char name[static SCORE_SIZE], and the two exact-size output buffers in scoreRangeBounds are upgraded from [SCORE_SIZE] to [static SCORE_SIZE], so the contract is visible at every call site and compilers can diagnose undersized buffers.

fbtreeSeekToScore, fbtreeDeleteRangeByScore and fbtreeCountRangeByScore are public, but only their definitions are annotated. A C99 array parameter with a static size qualifier is invalid C++, and fbtree.h is included by test_fbtree.cpp, so the header prototypes stay const char *; C permits a definition to carry array qualifiers its declaration lacks.

No behavioral change.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Reviewing files that changed from the base of the PR and between 5c24e5d and b3c260b.

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• src/fbtree.c

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📝 Walkthrough

Walkthrough

The change adds static SCORE_SIZE array bounds to score-related parameters and replaces a same-leaf early return in deleteRangeCore with an assertion that boundary leaves differ.

Changes

Score Range Contracts

Layer / File(s)	Summary
Score bounds and deletion invariant src/fbtree.c	Score lookup, range, deletion, and counting functions now declare score buffers with static SCORE_SIZE bounds. deleteRangeCore now asserts distinct boundary leaves instead of returning for same-leaf ranges.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~4 minutes

Merge Risk: ⚪ Minimal · up to b3c26

The cleanup preserves the existing score and deletion contracts, so the change is mergeable with normal checks.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main changes: removing the dead guard in deleteRangeCore and adding buffer contracts for ZSET score operations.
Description check	✅ Passed	The description is directly related to the changeset and clearly explains the assertion replacement, buffer annotations, C++ compatibility, and lack of behavioral change.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 1 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

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[valkey-review-bot]

The public score-buffer annotations introduce warnings in the default server build because their header declarations still use pointer parameters.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.82%. Comparing base (122ec7e) to head (b0e0534).
⚠️ Report is 2 commits behind head on unstable.

Files with missing lines	Patch %	Lines
src/fbtree.c	87.50%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #4715      +/-   ##
============================================
+ Coverage     80.63%   80.82%   +0.18%     
============================================
  Files           192      192              
  Lines        100803   100807       +4     
============================================
+ Hits          81287    81475     +188     
+ Misses        19516    19332     -184     

Files with missing lines	Coverage Δ
src/fbtree.c	95.49% <87.50%> (ø)

... and 24 files with indirect coverage changes

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