RFR: 8305913: com/sun/jdi/JdbLastErrorTest.java failed with '"lastError = 42' missing from stdout/stderr"

[Kevin Walls]

This test is failing often since 8304725 added a call to Thread::current_in_asgct().  This can end up being called e.g. when resolving calls, and then the OS last error value is lost.

The test is reliable with a single warm-up call to getLastError.invoke() before the loop.

The test was introduced when in JDK-8292302 a change was undone that had made JavaThread::threadObj call Thread::current_or_null_safe, as the use of TLS upset this case of accessing last error directly.

This new Thread::current_in_asgct() case shows that the VM will find new ways to interfere with the last error value, or at least new VM code keeps wanting to call Thread::current.  This testcase is kind of niche usage, so it not an argument that VM code should not be calling Thread::current.   If this test is to stay active, it needs to have this warm-up getLastError call.  (If there are more issues, it might mean removing the test.)

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Commit messages:
 - 8305913: com/sun/jdi/JdbLastErrorTest.java failed with '"lastError = 42' missing from stdout/stderr"

Changes: https://git.openjdk.org/jdk/pull/13481/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13481&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305913
  Stats: 6 lines in 2 files changed: 3 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13481.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13481/head:pull/13481

PR: https://git.openjdk.org/jdk/pull/13481