RFR: 8278965: crash in SymbolTable::do_lookup

Thu Feb 9 13:53:18 UTC 2023

Please review this small change to hold the refcount of a super class name while calling handle_parallel_super_load. Contrary to what I wrote in JDK-8298061, the refcount in the Placeholder table should never go to one.  I can reproduce this with btree012 occasionally, so this fixes this too.

The include in placeholders.hpp is required to make the gtest compiled since placeholders header file has Symbol::maybe_increment_refcount and decrement calls.

Tested with the graal test that failed, and tier1-7.

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Commit messages:
 - 8278965: crash in SymbolTable::do_lookup

Changes: https://git.openjdk.org/jdk/pull/12491/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12491&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8278965
  Stats: 119 lines in 3 files changed: 117 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/12491.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12491/head:pull/12491

PR: https://git.openjdk.org/jdk/pull/12491