Test case: for verifying main(String[]), run() method of Thread and its subclasses are marked entry frames

[zhengyu123]

What does this PR do?:
This PR is a test case for https://datadoghq.atlassian.net/browse/PROF-15782 and https://datadoghq.atlassian.net/browse/PROF-15781

Motivation:
Improve test coverage.

Additional Notes:

How to test the change?:
New test successfully verifies that void main(String[]), void run() of Thread and its subclasses are entry frames.

For Datadog employees:

• If this PR touches code that signs or publishes builds or packages, or handles
  credentials of any kind, I've requested a security review (run the dd:platform-security-review
  skill, or file a request via the PSEC review form).
  bewaire also runs automatically on every PR.
• This PR doesn't touch any of that.
• JIRA: PROF-15783

Unsure? Have a question? Request a review!

[dd-octo-sts]

Scan-Build Report

User:	runner@runnervmzvulz
Working Directory:	/home/runner/work/java-profiler/java-profiler/ddprof-lib/src/test/make
Command Line:	make -j4 all
Clang Version:	Ubuntu clang version 18.1.3 (1ubuntu1)
Date:	Tue Aug 18 14:24:55 2026

Bug Summary

Bug Type	Quantity	Display?
All Bugs	1
Logic error
Dereference of null pointer	1

Reports

Bug Group	Bug Type ▾	File	Function/Method	Line	Path Length
Logic error	Dereference of null pointer	profiler.h	findLibraryByAddress	523	28

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a new integration-style JFR test to validate that stack traces are (not) marked truncated depending on whether the bottom Java frame is a recognized thread entry point, along with the supporting workload and clarifying stack-frame ordering docs.

Changes:

• Added EntryFrameTest to assert truncation behavior for known entry points vs non-entry frames under shallow jstackdepth.
• Extended ExternalLauncher with an entry-frames workload that burns CPU on three different thread entry paths.
• Clarified JfrStackTrace.frames() Javadoc to document actual frame ordering as written by Recording::writeStackTraces.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
ddprof-test/src/test/java/com/datadoghq/profiler/jfr/EntryFrameTest.java	New test validating truncated semantics by bottom frame across multiple entry points and a negative control.
ddprof-test/src/test/java/com/datadoghq/profiler/JfrStackTrace.java	Updates documentation to match actual frame ordering used by the new test logic.
ddprof-test/src/test/java/com/datadoghq/profiler/ExternalLauncher.java	Adds an entry-frames workload to generate samples rooted at specific entry frames for the new test.

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[dd-octo-sts]

CI Test Results

Run: #32147945178 | Commit: 102fced | Duration: 14m 32s (longest job)

✅ All 32 test jobs passed

Status Overview

JDK	glibc-aarch64/debug	glibc-amd64/debug	musl-aarch64/debug	musl-amd64/debug
8	-	✅	-	-
8-ibm	-	✅	-	-
8-j9	✅	✅	-	-
8-librca	-	-	✅	✅
8-orcl	-	✅	-	-
11	-	✅	-	-
11-j9	✅	✅	-	-
11-librca	-	-	✅	✅
17	✅	✅	-	-
17-graal	✅	✅	-	-
17-j9	✅	✅	-	-
17-librca	-	-	✅	✅
21	✅	✅	-	-
21-graal	✅	✅	-	-
21-librca	-	-	✅	✅
25	✅	✅	-	-
25-graal	✅	✅	-	-
25-librca	-	-	✅	✅

Legend: ✅ passed | ❌ failed | ⚪ skipped | 🚫 cancelled

Summary: Total: 32 | Passed: 32 | Failed: 0

---

Updated: 2026-08-18 15:06:47 UTC

[dd-octo-sts]

✅ All 40 integration tests passed

📊 Dashboard · 👷 Pipeline · 📦 570311d4

[datadog-datadog-prod-us1]

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[kaahos]

looks good to me, thanks!

[jbachorik]

LGTM

BTW, this is exactly the kind of PRs when it's ok to merge without going through formal review. Localized, low impact, easy to review with tools.