LongHeap and TernaryLongHeap stop growing at 715,827,883 elements despite 'grows unbounded'

Finding LFV-069Area: util / heapsPriority: lowImpact: crashNovelty: new

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You push more than 715,827,882 elements into a growable LongHeap or TernaryLongHeap. You expect the heap to keep growing, as documented. Instead (size*3+1)/2 wraps, push throws and leaves the heap corrupt; TernaryLongHeap.downHeap has a related index overflow at the same size.

Expected vs actual

Expected: push(1) grows the array (to 1,207,959,553 slots) and size() is 715,827,883, or OutOfMemoryError if the heap is too small.
Actual: AssertionError: size must be positive (got -1073741823): likely integer overflow? from ArrayUtil.grow with assertions on; ArrayIndexOutOfBoundsException: Index 715827883 out of bounds for length 715827883 with them off.

Files

src/VerifyHeapPushGrowthOverflowTest.java (JUnit test)

Run it

Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
Tested on Lucene main b83101cdd2 (2026-10-23): reproduced.
How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.

# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble   (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar   # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar   # JUnit Platform console launcher (Maven Central)

javac -d classes -cp "$CP" $(find src -name '*.java')

# run 1: assertions on, seed DEADBEEF
java -ea -esa -Xmx2g --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF -Dtests.method=testGrowth* \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class VerifyHeapPushGrowthOverflowTest

Gradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).

Files shown on the finding page

TestLongHeapGrowthOverflow.java

Formal models and scripts this finding's part of the hunt used: study-overflow-at-scale

Feedback

Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.