unlink rolled-back keys from hash buckets on insert rollback

[Ramya-9353]

Repro: bulk-insert a range or initializer_list into a hash-mode object that already has spare capacity, where a later element throws (e.g. an allocation failure) after an earlier one has been inserted; a subsequent lookup reads a freed key (ASAN heap-use-after-free in find_in_object).

Cause: on the no-reallocation path revert_insert::destroy rolls back the partially inserted elements and the size, but insert_impl has already linked each of them into a bucket chain, and those bucket heads are left pointing at the slots that are then destroyed.

Fix: unlink the rolled-back elements from their buckets in revert_insert::destroy, on the no-reallocation path only, before they are destroyed. Both bulk-insert overloads share this path. Regression test in test/object.cpp fails under ASAN before the change and passes after.

[cppalliance-bot]

An automated preview of the documentation is available at https://1188.json.prtest2.cppalliance.org/libs/json/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-08-18 13:36:10 UTC

[cppalliance-bot]

GCOVR code coverage report https://1188.json.prtest2.cppalliance.org/gcovr/index.html
LCOV code coverage report https://1188.json.prtest2.cppalliance.org/genhtml/index.html
Coverage Diff Report https://1188.json.prtest2.cppalliance.org/diff-report/index.html

Build time: 2026-08-18 13:58:14 UTC

[cppalliance-bot]

Benchmark test results. More info at https://benchmark.cppalliance.org/jsonbenchmarks-pullrequests/1188/pullrequest.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.76%. Comparing base (e2f976c) to head (2296754).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1188      +/-   ##
===========================================
+ Coverage    93.71%   93.76%   +0.05%     
===========================================
  Files           85       85              
  Lines         8971     8986      +15     
===========================================
+ Hits          8407     8426      +19     
+ Misses         564      560       -4     

Files with missing lines	Coverage Δ
include/boost/json/impl/object.ipp	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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