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kalayciburak · 2026-09-08T10:34:38Z

StackWalkerStrategy.<clinit> loaded java.lang.StackWalker through the current thread's TCCL. When that loader is null (user threads that cleared it, or the JVM Attach Listener while a dynamic agent is installed), ReflectionUtils.tryLoadClass threw an uncaught NullPointerException. That failed class initialization and every later reference became NoClassDefFoundError: Could not initialize class ...StackWalkerStrategy.

Because console capture walks the stack on every println, a write from a null-TCCL thread could poison the forked JVM. On 3.6.0 this also surfaces as a confusing Byte Buddy / BlockHound self-attach failure when the JDK prints the dynamic-agent warning from Attach Listener.

This change:

treats a null ClassLoader as "not found" in tryLoadClass (ClassNotFoundException / NoClassDefFoundError only)
resolves StackWalker / StackFrame from StackWalkerStrategy's defining loader (system loader if that is bootstrap null), since those types are JDK classes and do not need the TCCL

Fixes #3460

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Validation (JDK 21, Maven 3.9.11):

mvn -pl surefire-api -Dtest=ReflectionUtilsTest,StackTraceProviderTest test — 23 tests, 0 failures
mvn -pl surefire-api test — 217 tests, 0 failures, 6 skipped

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MatthewRyanRead

Nice, hopefully they will accept this for 3.6.1.

elharo · 2026-09-09T11:14:51Z

    static {
-        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
+        // java.lang.StackWalker is a JDK class; do not depend on the current thread's TCCL, which can be null
+        // (Attach Listener, user threads that cleared it). A null TCCL used to NPE in tryLoadClass and poison


only describe current code, not what used to happen

elharo · 2026-09-09T11:15:21Z

        try {
            return classLoader.loadClass(className);
-        } catch (NoClassDefFoundError | ClassNotFoundException ignore) {
+        } catch (NoClassDefFoundError | ClassNotFoundException | RuntimeException ignore) {


return null should probably move into this catch block

Don't catch RuntimeException. Only catch more specific exceptions you actually expect. Otherwise we'll hide bugs we should know about

…TCCL tryLoadClass treated a null ClassLoader as loadClass on null and threw, which poisoned StackWalkerStrategy.<clinit> for the rest of the forked JVM. Load JDK types from the defining class loader instead, and treat a null loader as not found. Fixes apache#3460 Signed-off-by: Burak KALAYCI <kalayciburak1996@gmail.com>

olamy · 2026-09-10T02:47:47Z

+
+    @Test
+    void getStackDoesNotThrowWhenContextClassLoaderIsNull() {
+        ClassLoader original = Thread.currentThread().getContextClassLoader();


Thanks for your pull request.
Could you please provide an IT test as well. A real as simple as possible project reproducing the issue

added a tiny IT, same repro as on the issue (null TCCL thread + one println). pushed

Minimal project that prints from a thread whose context class loader is null, the same repro as on the issue.

maven-surefire-plugin and maven-failsafe-plugin 3.6.0 (bumped in #84) add StackWalkerStrategy, whose static initializer calls Thread.currentThread().getContextClassLoader().loadClass(...). The JVM's "Attach Listener" thread has no context class loader, so the initializer throws an NPE whenever that thread prints to the captured stdout/stderr. Mockito's self-attach prints the dynamic agent loading warning from that thread, so the agent fails to start ("Could not initialize plugin: interface org.mockito.plugins.MockMaker"), and every later console line in the same JVM fails with NoClassDefFoundError for StackWalkerStrategy. The fess-crawler CI build went from passing to failing on the same commit once the snapshot picked up 3.6.0. Running the same tests with the plugin version forced shows 13 errors with 3.6.0 and none with 3.5.6, and the whole fess-crawler module passes with 3.5.6. The upstream fix is SUREFIRE-3460 (apache/maven-surefire#3464), scheduled for 3.6.1, which is not released yet.

slawekjaranowski added the bug Something isn't working label Sep 8, 2026

MatthewRyanRead approved these changes Sep 9, 2026

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elharo requested changes Sep 9, 2026

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kalayciburak force-pushed the fix-3460-null-tccl-stackwalker branch from d3cd380 to 0349086 Compare September 9, 2026 12:11

olamy requested changes Sep 10, 2026

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[SUREFIRE-3460] Add IT for console capture with a null TCCL

9bab5e1

Minimal project that prints from a thread whose context class loader is null, the same repro as on the issue.

olamy merged commit b87cb03 into apache:master Sep 10, 2026
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github-actions Bot assigned olamy Sep 10, 2026

github-actions Bot added this to the 3.6.1 milestone Sep 10, 2026

yawkat mentioned this pull request Sep 12, 2026

Update dependency org.apache.maven.plugins:maven-surefire-plugin to v3.6.0 yawkat/lz4-java#90

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mathecruz mentioned this pull request Sep 28, 2026

Update quarkiverse-parent to 23 quarkiverse/quarkus-flow#1031

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gastaldi mentioned this pull request Sep 29, 2026

Update dependency io.quarkiverse:quarkiverse-parent to v23 quarkiverse/quarkus-vault#596

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marevol mentioned this pull request Oct 1, 2026

fix(build): go back to surefire and failsafe 3.5.6 codelibs/fess-parent#85

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olamy mentioned this pull request Oct 3, 2026

Fixing issues of new surefire mode using Junit Platform support-and-care/maven-support-and-care#246

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gastaldi mentioned this pull request Oct 13, 2026

Drop nexus-staging-maven-plugin and GPG signing from the release profile smallrye/smallrye-parent#691

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gastaldi mentioned this pull request Nov 4, 2026

@QuarkusTest discovery hang on 3.33.4.1: FacadeClassLoader vs ConsoleMavenTransferListener / StackWalkerStrategy quarkusio/quarkus#57796

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[SUREFIRE-3460] Don't NPE when StackWalkerStrategy inits with a null TCCL - #3464

[SUREFIRE-3460] Don't NPE when StackWalkerStrategy inits with a null TCCL#3464
olamy merged 2 commits into
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kalayciburak:fix-3460-null-tccl-stackwalker

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kalayciburak commented Sep 8, 2026 •

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