Bug ID: JDK-8322992 Javac fails with StackOverflowError when compiling deeply nested synchronized blocks

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JDK 21	JDK 23
21.0.9Fixed	23 b20Fixed

javac JavacBug.java

The system is out of resources.
Consult the following stack trace for details.
java.lang.StackOverflowError
	at jdk.compiler/com.sun.tools.javac.jvm.Code.emitStackMapFrame(Code.java:1366)
	at jdk.compiler/com.sun.tools.javac.jvm.Code.emitStackMap(Code.java:1261)
	at jdk.compiler/com.sun.tools.javac.jvm.Code.emitop(Code.java:388)
	at jdk.compiler/com.sun.tools.javac.jvm.Code.emitop1w(Code.java:938)
	at jdk.compiler/com.sun.tools.javac.jvm.Items$LocalItem.store(Items.java:409)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.genTry(Gen.java:1591)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitSynchronized(Gen.java:1489)
	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCSynchronized.accept(JCTree.java:1428)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.genDef(Gen.java:588)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:623)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStat(Gen.java:609)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.genStats(Gen.java:660)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.doVisitBlock(Gen.java:1102)
	at jdk.compiler/com.sun.tools.javac.jvm.Gen.visitBlock(Gen.java:1095)
	at jdk.compiler/com.sun.tools.javac.tree.JCTree$JCBlock.accept(JCTree.java:1092)

I bisected this and it seems to be a regression in JDK 20 b27. Relevant changes to javac:
https://bugs.openjdk.org/issues/?jql=project%20%3D%20JDK%20AND%20resolution%20%3D%20Fixed%20AND%20fixVersion%20%3D%20%2220%22%20AND%20component%20%3D%20tools%20AND%20%22Resolved%20In%20Build%22%20%3D%20b27%20AND%20Subcomponent%20%3D%20javac%20ORDER%20BY%20resolved%20DESC

Fix request [21u] I backport this to fix this obvious problem and as prereq of JDK-8332106. Low risk. Limited to javac, good repro case, no bugtail. Clean backport. Test passes and reproduces the issue. SAP nightly testing passed.
21-07-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk21u-dev/pull/1992 Date: 2025-07-19 19:10:32 +0000
19-07-2025
Please note that the new SOEDeeplyNestedBlocksTest is not passing in Linux x86 (I also commented in the PR). https://github.com/vicente-romero-oracle/jdk/actions/runs/8786696145/job/24111450455#step:9:17883
23-04-2024
Changeset: 0b9350e8 Author: Vicente Romero <vromero@openjdk.org> Date: 2024-04-22 16:31:32 +0000 URL: https://git.openjdk.org/jdk/commit/0b9350e8b619bc556f36652cde6f73211be5b85b
22-04-2024
A pull request was submitted for review. URL: https://git.openjdk.org/jdk/pull/18832 Date: 2024-04-18 01:24:01 +0000
18-04-2024
caused by JDK-8291769
16-04-2024

Causes :	JDK-8291769 - Translation of switch with record patterns could be improved
Relates :	JDK-8338567 - Deeply nested synchronized crashes javac
Relates :	JDK-8322996 - BoxLockNode creation fails with assert(reg < CHUNK_SIZE) failed: sanity