RFR: 8308762: Metaspace leak with Instrumentation.retransform

[Coleen Phillimore]

On Thu, 6 Jul 2023 05:18:01 GMT, Jean-Philippe Bempel <jpbempel at openjdk.org> wrote:

> Fix a small leak in constant pool merging during retransformation of a class. If this class has a catch block with `Throwable`, the class `Throwable` is pre-resolved in the constant pool, while all the other classes are in a unresolved state. So the constant pool merging process was considering the entry with pre-resolved class as different compared to the destination and create a new entry. We now try to consider it as equal specially for Methodref/Fieldref.

I wonder if compare_entry_to can just handle this case directly and not have this function.

src/hotspot/share/oops/constantPool.cpp line 1302:

> 1300:   if (strcmp(s1, s2) != 0) {
> 1301:     return false;  // strings don't match; not our special case
> 1302:   }

klass_name_at() returns a Symbol* that's in the SymbolTable so this never needed to do a strcmp.  It can test for equality.

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Changes requested by coleenp (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/14780#pullrequestreview-1516550061
PR Review Comment: https://git.openjdk.org/jdk/pull/14780#discussion_r1254440703