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https://issues.apache.org/jira/browse/FLINK-40605?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
ASF GitHub Bot updated FLINK-40605:
-----------------------------------
Labels: pull-request-available (was: )
> Code splitting still exceeds 64 KB for large if blocks containing loops with
> break or continue
> ----------------------------------------------------------------------------------------------
>
> Key: FLINK-40605
> URL: https://issues.apache.org/jira/browse/FLINK-40605
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Runtime
> Affects Versions: 2.4.0
> Environment: Apache Flink master / 2.4-SNAPSHOT at
> 4e9d5412d3dcd4776b750e8a94ba6e86d2b409c6; JDK 17; Janino 3.1.12; repository
> Maven wrapper 3.9.16. Reproduced on 9 September 2026.
> Reporter: Moses
> Priority: Major
> Labels: pull-request-available
>
> h2. Problem
> A large generated {{if}} block can still fail Janino compilation with {{Code
> grows beyond 64 KB}} when it contains a small, self-contained loop with
> {{break}} or {{continue}}, even after the full
> {{JavaCodeSplitter.split(...)}} pipeline has run.
> This is a remaining code-splitting corner case, rather than a request to
> reopen FLINK-23007. FLINK-23007 introduced the splitter, and FLINK-27246
> subsequently added block rewriting. The current implementation still
> conservatively rejects an enclosing statement whenever any descendant
> contains a jump.
> h2. Reproduction
> Reproduced on Apache Flink {{master}} / {{2.4-SNAPSHOT}} at commit
> {{4e9d5412d3dcd4776b750e8a94ba6e86d2b409c6}} on 9 September 2026, with JDK 17
> and Janino 3.1.12. Released versions have not been tested for this specific
> reproduction.
> Run the following with {{JavaCodeSplitter}} and Janino on the classpath.
> Repeat with {{jump = "continue"}} to reproduce the second case.
> {code:java}
> import org.apache.flink.table.codesplit.JavaCodeSplitter;
> import org.codehaus.janino.SimpleCompiler;
> public class CodeSplitReproducer {
> public static void main(String[] args) throws Exception {
> String jump = "break";
> String code =
> "public class Generated { public void run(int[] a) {"
> + "if (a[0] >= 0) {"
> + "a[1] += 1;".repeat(15000)
> + "for (int i = 0; i < 5; i++) {"
> + "a[2]++; if (i == 2) { " + jump + "; } a[3]++;"
> + "}} a[4] = 1; }}";
> String split = JavaCodeSplitter.split(code, 4000, 10000);
> SimpleCompiler compiler = new SimpleCompiler();
> compiler.cook(split);
> Class<?> generated = compiler.getClassLoader().loadClass("Generated");
> Object instance = generated.getDeclaredConstructor().newInstance();
> int[] result = {0, 0, 0, 0, 0};
> generated.getMethod("run", int[].class).invoke(instance, result);
> System.out.println(java.util.Arrays.toString(result));
> }
> }
> {code}
> *Actual:* compilation of the transformed code fails with:
> {noformat}
> Caused by: org.codehaus.commons.compiler.InternalCompilerException: Code
> grows beyond 64 KB
> {noformat}
> *Expected:* the large enclosing block is split into compilable methods
> without changing control flow. The result is {{[0, 15000, 3, 2, 1]}} for
> {{break}} and {{[0, 15000, 5, 4, 1]}} for {{continue}}. For an input of
> {{[-1, 0, 0, 0, 0]}}, the branch is skipped and the result is {{[-1, 0, 0, 0,
> 1]}}.
> h2. Cause and proposed fix
> {{BlockStatementSplitter.BlockStatementVisitor.visitStatement}} currently
> returns early when {{getNumOfReturnOrJumpStatements(ctx) != 0}}. Counting
> every nested {{break}}/{{continue}} prevents splitting the entire enclosing
> {{if}}, even though the loop and its jump targets can remain together inside
> an extracted method.
> Track returns separately, retain the conservative return guard and the jump
> guard when traversing loop bodies, and allow enclosing blocks containing
> complete loops to be extracted. This does not attempt to support arbitrary
> oversized loop bodies containing jumps.
> h2. Patch and verification
> A candidate fix with regression tests is available in [this fork
> commit|https://github.com/ChaomingZhangCN/flink/commit/12da06a50a0e7fe321560b28c9ab1b65f4fd9a53]
> (branch {{codex/fix-code-splitter-nested-jumps}}).
> * Both oversized-branch regression cases fail on the unmodified base commit
> with the 64 KB error and pass with the fix.
> * Execution assertions cover {{break}}, {{continue}}, skipped branches,
> labeled jumps and early returns.
> * The complete code-splitter module suite passes against its {{2.4-SNAPSHOT}}
> reactor dependencies: 54 tests, 0 failures, 0 errors and 1 pre-existing
> skipped test.
> * Spotless, Checkstyle and a module-scoped RAT check pass. The full
> repository test suite has not been run.
> Related: FLINK-23007 and FLINK-27246.
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