[Marti2203]

Summary

MakeSharedCappedKeySegmentsExtractor() crashes for more than 6 byte widths:

auto ex = experimental::MakeSharedCappedKeySegmentsExtractor({1, 1, 1, 1, 1, 1, 1});  // segfault

For 0 to 6 widths it returns a SemiStaticCappedKeySegmentsExtractor<N> (a std::array). For more it returns a DynamicCappedKeySegmentsExtractor, whose constructor assigns ideal_ends_[i] while ideal_ends_ is still an empty std::vector, so it writes past the end of the vector. If it did not crash, Extract() would return no segments, since it copies ideal_ends_.

The fix sizes ideal_ends_ before filling it.

Test plan

DBBloomFilterTest.FixedWidthSegments now also covers a 7-width extractor ({1, 2, 0, 1, 1, 1, 1}): its id, and the extracted segment sizes for an empty key, a short key, an exact-length key and a longer key, matching the 4-width cases already there.

• Without the fix: the test segfaults while creating the extractor.
• With the fix: FixedWidthSegments and SstQueryFilter pass.

cmake --build <build> --target db_bloom_filter_test
./db_bloom_filter_test --gtest_filter='DBBloomFilterTest.FixedWidthSegments:DBBloomFilterTest.SstQueryFilter'

Debug build, clang 21. Independent of #15523, which fixes the decoding of SelectKeySegmentRange in the same file.

This issue was found by an LLM-Enhanced Static Analysis Engine and verified manually.